69 results on '"Melissa D. Conrad"'
Search Results
2. Susceptibility of Ugandan Plasmodium falciparum Isolates to the Antimalarial Drug Pipeline
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Oriana Kreutzfeld, Patrick K. Tumwebaze, Martin Okitwi, Stephen Orena, Oswald Byaruhanga, Thomas Katairo, Melissa D. Conrad, Stephanie A. Rasmussen, Jennifer Legac, Ozkan Aydemir, David Giesbrecht, Barbara Forte, Peter Campbell, Alasdair Smith, Hiroki Kano, Samuel L. Nsobya, Benjamin Blasco, Maelle Duffey, Jeffrey A. Bailey, Roland A. Cooper, and Philip J. Rosenthal
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Plasmodium falciparum ,Ugandan field isolates ,antimalarials ,drug resistance ,genotypic identification ,malaria ,Microbiology ,QR1-502 - Abstract
ABSTRACT Malaria, especially Plasmodium falciparum infection, remains an enormous problem, and its treatment and control are seriously challenged by drug resistance. New antimalarial drugs are needed. To characterize the Medicines for Malaria Venture pipeline of antimalarials under development, we assessed the ex vivo drug susceptibilities to 19 compounds targeting or potentially impacted by mutations in P. falciparum ABC transporter I family member 1, acetyl-CoA synthetase, cytochrome b, dihydroorotate dehydrogenase, elongation factor 2, lysyl-tRNA synthetase, phenylalanyl-tRNA synthetase, plasmepsin X, prodrug activation and resistance esterase, and V-type H+ ATPase of 998 fresh P. falciparum clinical isolates collected in eastern Uganda from 2015 to 2022. Drug susceptibilities were assessed by 72-h growth inhibition (half-maximum inhibitory concentration [IC50]) assays using SYBR green. Field isolates were highly susceptible to lead antimalarials, with low- to midnanomolar median IC50s, near values previously reported for laboratory strains, for all tested compounds. However, outliers with decreased susceptibilities were identified. Positive correlations between IC50 results were seen for compounds with shared targets. We sequenced genes encoding presumed targets to characterize sequence diversity, search for polymorphisms previously selected with in vitro drug pressure, and determine genotype-phenotype associations. We identified many polymorphisms in target genes, generally in
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- 2023
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3. Balanced impacts of fitness and drug pressure on the evolution of PfMDR1 polymorphisms in Plasmodium falciparum
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Marvin Duvalsaint, Melissa D. Conrad, Stephen Tukwasibwe, Patrick K. Tumwebaze, Jennifer Legac, Roland A. Cooper, and Philip J. Rosenthal
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Malaria ,Plasmodium falciparum ,Drug resistance ,Fitness ,PfMDR1 ,Arctic medicine. Tropical medicine ,RC955-962 ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Anti-malarial drug resistance may be limited by decreased fitness in resistant parasites. Important contributors to resistance are mutations in the Plasmodium falciparum putative drug transporter PfMDR1. Methods Impacts on in vitro fitness of two common PfMDR1 polymorphisms, N86Y, which is associated with sensitivity to multiple drugs, and Y184F, which has no clear impact on drug sensitivity, were evaluated to study associations between resistance mediators and parasite fitness, measured as relative growth in competitive culture experiments. NF10 P. falciparum lines engineered to represent all PfMDR1 N86Y and Y184F haplotypes were co-cultured for 40 days, and the genetic make-up of the cultures was characterized every 4 days by pyrosequencing. The impacts of culture with anti-malarials on the growth of different haplotypes were also assessed. Lastly, the engineering of P. falciparum containing another common polymorphism, PfMDR1 D1246Y, was attempted. Results Co-culture results were as follows. With wild type (WT) Y184 fixed (N86/Y184 vs. 86Y/Y184), parasites WT and mutant at 86 were at equilibrium. With mutant 184 F fixed (N86/184F vs. 86Y/184F), mutants at 86 overgrew WT. With WT N86 fixed (N86/Y184 vs. N86/184F), WT at 184 overgrew mutants. With mutant 86Y fixed (86Y/Y184 vs. 86Y/184F), WT and mutant at 86 were at equilibrium. Parasites with the double WT were in equilibrium with the double mutant, but 86Y/Y184 overgrew N86/184F. Overall, WT N86/mutant 184F parasites were less fit than parasites with all other haplotypes. Parasites engineered for another mutation, PfMDR1 1246Y, were unstable in culture, with reversion to WT over time. Thus, the N86 WT is stable when accompanied by the Y184 WT, but incurs a fitness cost when accompanied by mutant 184F. Culturing in the presence of chloroquine favored 86Y mutant parasites and in the presence of lumefantrine favored N86 WT parasites; piperaquine had minimal impact. Conclusions These results are consistent with those for Ugandan field isolates, suggest reasons for varied haplotypes, and highlight the interplay between drug pressure and fitness that is guiding the evolution of resistance-mediating haplotypes in P. falciparum.
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- 2021
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4. Deletions of pfhrp2 and pfhrp3 genes were uncommon in rapid diagnostic test-negative Plasmodium falciparum isolates from Uganda
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Sam L. Nsobya, Andrew Walakira, Elizabeth Namirembe, Moses Kiggundu, Joaniter I. Nankabirwa, Emmanuel Ruhamyankaka, Emmanuel Arinaitwe, Melissa D. Conrad, Moses R. Kamya, Grant Dorsey, and Philip J. Rosenthal
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pfhrp2 ,pfhrp3 ,Plasmodium falciparum ,HRP2 ,Rapid diagnostic test ,Arctic medicine. Tropical medicine ,RC955-962 ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Rapid diagnostic tests (RDTs) play a key role in malaria case management. The most widely used RDT identifies Plasmodium falciparum based on immunochromatographic recognition of P. falciparum histidine-rich protein 2 (PfHRP2). Deletion of the paralogous pfhrp2 and pfhrp3 genes leads to false-negative PfHRP2-based RDTs, and has been reported in P. falciparum infections from South America and Africa. However, identification of pfhrp2/pfhrp3 deletions has usually been based only on failure to amplify these genes using PCR, without confirmation based on PfHRP2 protein expression, and understanding of the true prevalence of deletions is incomplete. Methods Deletions of pfhrp2/pfhrp3 in blood samples were investigated from cross-sectional surveys in 2012-13 in three regions of varied malaria transmission intensity in Uganda. Samples with positive Giemsa-stained thick blood smears, but negative PfHRP2-based RDTs were evaluated by PCR amplification of conserved subunit ribosomal DNA for Plasmodium species, PCR amplification of pfhrp2 and pfhrp3 genes to identify deletions, and bead-based immunoassays for expression of PfHRP2. Results Of 3516 samples collected in cross-sectional surveys, 1493 (42.5%) had positive blood smears, of which 96 (6.4%) were RDT-negative. Of these 96 RDT-negative samples, P. falciparum DNA was identified by PCR in 56 (58%) and only non-falciparum plasmodial DNA in 40 (42%). In all 56 P. falciparum-positive samples there was a failure to amplify pfhrp2 or pfhrp3: in 25 (45%) pfhrp2 was not amplified, in 39 (70%) pfhrp3 was not amplified, and in 19 (34%) neither gene was amplified. For the 39 P. falciparum-positive, RDT-negative samples available for analysis of protein expression, PfHRP2 was not identified by immunoassay in only four samples (10.3%); these four samples all had failure to amplify both pfhrp2 and pfhrp3 by PCR. Thus, only four of 96 (4.2%) smear-positive, RDT-negative samples had P. falciparum infections with deletion of pfhrp2 and pfhrp3 confirmed by failure to amplify the genes by PCR and lack of expression of PfHRP2 demonstrated by immunoassay. Conclusion False negative RDTs were uncommon. Deletions in pfhrp2 and pfhrp3 explained some of these false negatives, but most false negatives were not due to deletion of the pfhrp2 and pfhrp3 genes.
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- 2021
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5. Identification and characterization of immature Anopheles and culicines (Diptera: Culicidae) at three sites of varying malaria transmission intensities in Uganda
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Alex K. Musiime, David L. Smith, Maxwell Kilama, Otto Geoffrey, Patrick Kyagamba, John Rek, Melissa D. Conrad, Joaniter I. Nankabirwa, Emmanuel Arinaitwe, Anne M. Akol, Moses R. Kamya, Grant Dorsey, Sarah G. Staedke, Chris Drakeley, and Steve W. Lindsay
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Anopheles ,Culicine ,Anopheline ,Larvae ,Pupae ,Aquatic habitats ,Arctic medicine. Tropical medicine ,RC955-962 ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Over the last two decades, there has been remarkable progress in malaria control in sub-Saharan Africa, due mainly to the massive deployment of long-lasting insecticidal nets and indoor residual spraying. Despite these gains, it is clear that in many situations, additional interventions are needed to further reduce malaria transmission. The World Health Organization (WHO) has promoted the Integrated Vector Management (IVM) approach through its Global Vector Control Response 2017–2030. However, prior roll-out of larval source management (LSM) as part of IVM, knowledge on ecology of larval aquatic habitats is required. Methods Aquatic habitats colonized by immature Anopheles and culicines vectors were characterized at three sites of low, medium and high malaria transmission in Uganda from October 2011 to June 2015. Larval surveys were conducted along transects in each site and aquatic habitats described according to type and size. Immature Anopheles, culicines and pupae from the described habitats were sampled using standard dipping methods to determine larval and pupae densities. Larvae were identified as anopheline or culicine, and counted. Pupae were not identified further. Binary logistic regression analysis was used to identify factors associated with the presence of immature Anopheles and culicines in each site. Results A total of 1205 larval aquatic habitats were surveyed and yielded a total of 17,028 anopheline larvae, 26,958 culicine larvae and 1189 pupae. Peaks in larval abundance occurred in all sites in March–May and August-October coinciding with the rainy seasons. Anopheles larvae were found in 52.4% (n = 251) of aquatic habitats in Tororo, a site of high transmission, 41.9% (n = 536) of habitats in Kanungu, a site with moderate malaria transmission, and 15.8% (n = 418) in Jinja, a site with low malaria transmission. The odds of finding larvae was highest in rice fields compared to pools in both Tororo (odds ratio, OR = 4.21, 95% CI 1.22–14.56, p = 0.02) and Kanungu (OR = 2.14, 95% CI 1.12–4.07, p = 0.02), while in Jinja the odd were highest in containers (OR = 4.55, 95% CI = 1.09–19.14, p = 0.03). In Kanungu, larvae were less likely to be found in containers compared to pools (OR = 0.26, 95% CI 0.09–0.66, p = 0.008) and river fringe (OR = 0.19, 95% CI 0.07–0.52, p = 0.001). Medium sized habitats were associated with high odds of finding larvae compared to small habitats (OR = 3.59, 95% CI 1.18–14.19, p = 0.039). Conclusions These findings show that immature Anopheles and culicines were common in areas of high and moderate transmission but were rare in areas of low transmission. Although immature Anopheles and culicines were found in all types of water bodies, they were most common in rice fields and less common in open drains and in river fringes. Methods are needed to reduce the aquatic stages of anopheline mosquitoes in human-made habitats, particularly rice fields.
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- 2020
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6. House design and risk of malaria, acute respiratory infection and gastrointestinal illness in Uganda: A cohort study
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Alex K. Musiime, Paul J. Krezanoski, David L. Smith, Maxwell Kilama, Melissa D. Conrad, Geoffrey Otto, Patrick Kyagamba, Jackson Asiimwe, John Rek, Joaniter I. Nankabirwa, Emmanuel Arinaitwe, Anne M. Akol, Moses R. Kamya, Sarah G. Staedke, Chris Drakeley, Teun Bousema, Steve W. Lindsay, Grant Dorsey, and Lucy S. Tusting
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Public aspects of medicine ,RA1-1270 - Abstract
House construction is rapidly modernizing across Africa but the potential benefits for human health are poorly understood. We hypothesised that improvements to housing would be associated with reductions in malaria, acute respiratory infection (ARI) and gastrointestinal illness in an area of low malaria endemicity in Uganda. Data were analysed from a cohort study of male and female child and adult residents (n = 531) of 80 randomly-selected households in Nagongera sub-county, followed for 24 months (October 4, 2017 to October 31, 2019). Houses were classified as modern (brick walls, metal roof and closed eaves) or traditional (all other homes). Light trap collections of mosquitoes were done every two weeks in all sleeping rooms. Every four weeks, we measured malaria infection (using microscopy and qPCR to detect malaria parasites), incidence of malaria, ARI and gastrointestinal illness. We collected 15,780 adult female Anopheles over 7,631 nights. We collected 13,277 blood samples of which 10.2% (1,347) were positive for malaria parasites. Over 958 person years we diagnosed 38 episodes of uncomplicated malaria (incidence 0.04 episodes per person-year at risk), 2,553 episodes of ARI (incidence 2.7 episodes per person-year) and 387 episodes of gastrointestinal illness (incidence 0.4 episodes per person-year). Modern houses were associated with a 53% lower human biting rate compared to traditional houses (adjusted incidence rate ratio [aIRR] 0.47, 95% confidence interval [CI] 0.32–0.67, p
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- 2022
7. Impact of vector control interventions on malaria transmission intensity, outdoor vector biting rates and Anopheles mosquito species composition in Tororo, Uganda
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Alex K. Musiime, David L. Smith, Maxwell Kilama, John Rek, Emmanuel Arinaitwe, Joaniter I. Nankabirwa, Moses R. Kamya, Melissa D. Conrad, Grant Dorsey, Anne M. Akol, Sarah G. Staedke, Steve W. Lindsay, and James P. Egonyu
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Indoor residual spraying ,Long-lasting insecticide nets ,Malaria vector ,Transmission ,Biting rates ,Arctic medicine. Tropical medicine ,RC955-962 ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are widely recommended for the prevention of malaria in endemic regions. Data from human landing catches provide information on the impact of vector control on vector populations. Here, malaria transmission indoors and outdoors, before and after mass deployment of LLINs and IRS in Uganda was compared. Methods The study took place in Tororo district, a historically high transmission area where universal LLIN distribution was conducted in November 2013 and May 2017 and 6 rounds of IRS implemented from December 2014 to July 2018. Human landing catches were performed in 8 houses monthly from October 2011 to September 2012 (pre-intervention period) and every 4 weeks from November 2017 to October 2018 (post-intervention period). Mosquitoes were collected outdoors from 18:00 to 22:00 h and indoors from 18:00 to 06:00 h. Female Anopheles were tested for the presence of Plasmodium falciparum sporozoites and species identification performed using gross dissection and polymerase chain reaction (PCR). Results The interventions were associated with a decline in human biting rate from 19.6 to 2.3 female Anopheles mosquitoes per house per night (p
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- 2019
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8. Seasonal malaria chemoprevention drug levels and drug resistance markers in children with or without malaria in Burkina Faso: a case control study
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Michelle E Roh, Issaka Zongo, Alassane Haro, Liusheng Huang, Anyirékun Fabrice Somé, Rakiswendé Serge Yerbanga, Melissa D Conrad, Erika Wallender, Jennifer Legac, Francesca Aweeka, Jean-Bosco Ouédraogo, and Philip J Rosenthal
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Infectious Diseases ,Immunology and Allergy - Abstract
Background Despite scale-up of seasonal malaria chemoprevention (SMC) with sulfadoxine-pyrimethamine and amodiaquine (SP-AQ) in children Methods We enrolled 310 children presenting at health facilities in Bobo-Dioulasso. Cases were SMC-eligible children 6-59 months of age diagnosed with malaria. Two controls were enrolled per case: SMC-eligible children without malaria and older (5-10 years old), SMC-ineligible children with malaria. We measured SP-AQ drug levels among SMC-eligible children and SP-AQ resistance markers among parasitemic children. Conditional logistic regression was used to compute odds ratios (ORs) comparing drug levels between cases and controls. Results Compared to SMC-eligible controls, children with malaria were less likely to have any detectable SP or AQ (OR = 0.33 [95% CI: 0.16-0.67]; p = 0.002) and have lower drug levels (p 0.05). Conclusion Incident malaria among SMC-eligible children was likely due to suboptimal levels of SP-AQ, resulting from missed cycles, rather than increased antimalarial resistance to SP-AQ.
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- 2023
9. Asymptomatic School-Aged Children Are Important Drivers of Malaria Transmission in a High Endemicity Setting in Uganda
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John Rek, Sara Lynn Blanken, Joseph Okoth, Daniel Ayo, Ismail Onyige, Eric Musasizi, Jordache Ramjith, Chiara Andolina, Kjerstin Lanke, Emmanuel Arinaitwe, Peter Olwoch, Katharine A Collins, Moses R Kamya, Grant Dorsey, Chris Drakeley, Sarah G Staedke, Teun Bousema, and Melissa D Conrad
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Adolescent ,Plasmodium falciparum ,lnfectious Diseases and Global Health Radboud Institute for Molecular Life Sciences [Radboudumc 4] ,Burkitt Lymphoma ,Malaria ,Women's cancers Radboud Institute for Health Sciences [Radboudumc 17] ,lnfectious Diseases and Global Health Radboud Institute for Health Sciences [Radboudumc 4] ,Infectious Diseases ,Child, Preschool ,Anopheles ,Animals ,Humans ,Immunology and Allergy ,Uganda ,Malaria, Falciparum ,Child ,Asymptomatic Infections - Abstract
Contains fulltext : 282499.pdf (Publisher’s version ) (Open Access) Achieving malaria elimination requires a better understanding of the transmissibility of human infections in different transmission settings. This study aimed to characterize the human infectious reservoir in a high endemicity setting in eastern Uganda, using gametocyte quantification and mosquito feeding assays. In asymptomatic infections, gametocyte densities were positively associated with the proportion of infected mosquitoes (β = 1.60; 95% CI, 1.32-1.92; P
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- 2022
10. Drug susceptibility of Plasmodium falciparum in eastern Uganda: a longitudinal phenotypic and genotypic study
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Stephen Orena, Frida G. Ceja, Brett R. Bayles, Melissa D. Conrad, Thomas Katairo, Jennifer Legac, Jeffrey A. Bailey, Martin Okitwi, Philip J. Rosenthal, Sevil Chelebieva, Stephanie A Rasmussen, Victor Asua, Roland A. Cooper, Samuel L. Nsobya, Oswald Byaruhanga, Ozkan Aydemir, Marvin Duvalsaint, and Patrick K Tumwebaze
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Microbiology (medical) ,Medicine (General) ,Genotype ,medicine.medical_treatment ,Plasmodium falciparum ,Dihydroartemisinin ,Drug resistance ,Lumefantrine ,Microbiology ,Article ,Antimalarials ,chemistry.chemical_compound ,R5-920 ,Virology ,Piperaquine ,parasitic diseases ,medicine ,Humans ,Uganda ,Longitudinal Studies ,Prospective Studies ,Malaria, Falciparum ,Pyronaridine ,biology ,Mefloquine ,business.industry ,Chloroquine ,biology.organism_classification ,medicine.disease ,QR1-502 ,Phenotype ,Infectious Diseases ,chemistry ,business ,Malaria ,medicine.drug - Abstract
Summary: Background: Treatment and control of malaria depends on artemisinin-based combination therapies (ACTs) and is challenged by drug resistance, but thus far resistance to artemisinins and partner drugs has primarily occurred in southeast Asia. The aim of this study was to characterise antimalarial drug susceptibility of Plasmodium falciparum isolates from Tororo and Busia districts in Uganda. Methods: In this prospective longitudinal study, P falciparum isolates were collected from patients aged 6 months or older presenting at the Tororo District Hospital (Tororo district, a site with relatively low malaria incidence) or Masafu General Hospital (Busia district, a high-incidence site) in eastern Uganda with clinical symptoms of malaria, a positive Giemsa-stained blood film for P falciparum, and no signs of severe disease. Ex-vivo susceptibilities to ten antimalarial drugs were measured using a 72-h microplate growth inhibition assay with SYBR Green detection. Relevant P falciparum genetic polymorphisms were characterised by molecular methods. We compared results with those from earlier studies in this region and searched for associations between drug susceptibility and parasite genotypes. Findings: From June 10, 2016, to July 29, 2019, 361 P falciparum isolates were collected in the Busia district and 79 in the Tororo district from 440 participants. Of 440 total isolates, 392 (89%) successfully grew in culture and showed excellent drug susceptibility for chloroquine (median half-maximal inhibitory concentration [IC50] 20·0 nM [IQR 12·0–26·0]), monodesethylamodiaquine (7·1 nM [4·3–8·9]), pyronaridine (1·1 nM [0·7–2·3]), piperaquine (5·6 nM [3·3–8·6]), ferroquine (1·8 nM [1·5–3·3]), AQ-13 (24·0 nM [17·0–32·0]), lumefantrine (5·1 nM [3·2–7·7]), mefloquine (9·5 nM [6·6–13·0]), dihydroartemisinin (1·5 nM [1·0–2·0]), and atovaquone (0·3 nM [0·2–0·4]). Compared with results from our study in 2010–13, significant improvements in susceptibility were seen for chloroquine (median IC50 288·0 nM [IQR 122·0–607·0]; p100 nM) was more common in isolates from the Tororo district (11 [15%] of 71), compared with those from the Busia district (12 [4%] of 320; p=0·0017). We showed significant increases between 2010–12 and 2016–19 in the prevalences of wild-type P falciparum multidrug resistance protein 1 (PfMDR1) Asn86Tyr from 60% (391 of 653) to 99% (418 of 422; p
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- 2021
11. Susceptibilities of Ugandan Plasmodium falciparum Isolates to Proteasome Inhibitors
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Shreeya Garg, Oriana Kreutzfeld, Sevil Chelebieva, Patrick K. Tumwebaze, Oswald Byaruhanga, Martin Okitwi, Stephen Orena, Thomas Katairo, Samuel L. Nsobya, Melissa D. Conrad, Ozkan Aydemir, Jennifer Legac, Alexandra E. Gould, Brett R. Bayles, Jeffrey A. Bailey, Maelle Duffey, Gang Lin, Laura A. Kirkman, Roland A. Cooper, and Philip J. Rosenthal
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Falciparum ,Proteasome Endopeptidase Complex ,Plasmodium falciparum ,Drug Resistance ,Microbiology ,Antimalarials ,Rare Diseases ,Mechanisms of Resistance ,Genetics ,Humans ,Pharmacology (medical) ,Uganda ,Malaria, Falciparum ,antimalarial agents ,Pharmacology ,Pharmacology and Pharmaceutical Sciences ,Ethylenediamines ,Malaria ,Vector-Borne Diseases ,proteasome ,Infectious Diseases ,Good Health and Well Being ,5.1 Pharmaceuticals ,Medical Microbiology ,Asparagine ,Development of treatments and therapeutic interventions ,Peptides ,Proteasome Inhibitors ,Biotechnology - Abstract
The proteasome is a promising target for antimalarial chemotherapy. We assessed ex vivo susceptibilities of fresh Plasmodium falciparum isolates from eastern Uganda to seven proteasome inhibitors: two asparagine ethylenediamines, two macrocyclic peptides, and three peptide boronates; five had median IC(50) values
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- 2022
12. Age-Related Changes in Malaria Clinical Phenotypes During Infancy Are Modified by Sickle Cell Trait
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Richard Kajubi, Moses R. Kamya, Melissa D. Conrad, Felistas Nankya, Teddy Andra, Harriet Adrama, Abel Kakuru, Nicholas Zehner, Isabel Rodriguez-Barraquer, Grant Dorsey, Tamara D. Clark, and Prasanna Jagannathan
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0301 basic medicine ,Parasitemia ,Rate ratio ,Medical and Health Sciences ,0302 clinical medicine ,malaria in infancy ,Medicine ,2.2 Factors relating to the physical environment ,030212 general & internal medicine ,Aetiology ,Malaria, Falciparum ,Pediatric ,biology ,Biological Sciences ,Infectious Diseases ,AcademicSubjects/MED00290 ,Phenotype ,medicine.symptom ,Infection ,Microbiology (medical) ,Falciparum ,medicine.medical_specialty ,030106 microbiology ,Plasmodium falciparum ,Asymptomatic ,Microbiology ,Sickle Cell Trait ,03 medical and health sciences ,Rare Diseases ,Clinical Research ,Internal medicine ,parasitic diseases ,Humans ,Sickle cell trait ,business.industry ,Infant ,biology.organism_classification ,medicine.disease ,asymptomatic parasitemia ,Confidence interval ,Malaria ,Clinical trial ,Vector-Borne Diseases ,Major Articles and Commentaries ,Good Health and Well Being ,business ,sickle cell trait - Abstract
Background Infants are protected against Plasmodium falciparum malaria. Mechanisms that drive this protection remain unclear due to a poor understanding of malaria clinical phenotypes during infancy. Methods We enrolled a birth cohort of 678 infants in Busia, Uganda, an area of high malaria transmission. We followed infants through 12 months of age and quantified protection against parasitemia and clinical disease. Results Symptomatic malaria incidence increased from 1.2 to 2.6 episodes per person-year between 0 and, In 678 Ugandan infants followed through 12 months of age, 1131 malaria episodes were observed. Age-dependent changes in sickle cell trait (HbAS) protective efficacy were accompanied by differential loss of antiparasite and antidisease protection among HbAS and HbAA infants.
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- 2021
13. Changing Prevalence of Potential Mediators of Aminoquinoline, Antifolate, and Artemisinin Resistance Across Uganda
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Adoke Yeka, Melissa D. Conrad, Sam L. Nsobya, Roland A. Cooper, Deborah M Chin, Jennifer Legac, Moses R. Kamya, Jeffrey A. Bailey, Philip J. Rosenthal, Ozkan Aydemir, Elias Duarte, Grant Dorsey, Patrick K Tumwebaze, Victor Asua, and Marvin Duvalsaint
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0301 basic medicine ,Drug Resistance ,PfMDR1 ,Drug resistance ,medicine.disease_cause ,Medical and Health Sciences ,0302 clinical medicine ,Pregnancy ,Multidrug Resistance Protein 1 ,Prevalence ,Immunology and Allergy ,Uganda ,Malaria, Falciparum ,Artemisinin ,Mutation ,Biological Sciences ,Artemisinins ,Infectious Diseases ,5.1 Pharmaceuticals ,Aminoquinolines ,PfDHFR ,Female ,Development of treatments and therapeutic interventions ,Infection ,medicine.drug ,Falciparum ,PfCRT ,Plasmodium falciparum ,030106 microbiology ,030231 tropical medicine ,Biology ,Microbiology ,Major Articles and Brief Reports ,Antimalarials ,03 medical and health sciences ,Rare Diseases ,Piperaquine ,parasitic diseases ,Genetics ,medicine ,Humans ,PfK13 ,biology.organism_classification ,medicine.disease ,Virology ,Malaria ,Vector-Borne Diseases ,Good Health and Well Being ,Folic Acid Antagonists ,Antimicrobial Resistance ,Dihydropteroate synthase ,PfDHPS - Abstract
Background In Uganda, artemether-lumefantrine is recommended for malaria treatment and sulfadoxine-pyrimethamine for chemoprevention during pregnancy, but drug resistance may limit efficacies. Methods Genetic polymorphisms associated with sensitivities to key drugs were characterized in samples collected from 16 sites across Uganda in 2018 and 2019 by ligase detection reaction fluorescent microsphere, molecular inversion probe, dideoxy sequencing, and quantitative polymerase chain reaction assays. Results Considering transporter polymorphisms associated with resistance to aminoquinolines, the prevalence of Plasmodium falciparum chloroquine resistance transporter (PfCRT) 76T decreased, but varied markedly between sites (0–46% in 2018; 0–23% in 2019); additional PfCRT polymorphisms and plasmepsin-2/3 amplifications associated elsewhere with resistance to piperaquine were not seen. For P. falciparum multidrug resistance protein 1, in 2019 the 86Y mutation was absent at all sites, the 1246Y mutation had prevalence ≤20% at 14 of 16 sites, and gene amplification was not seen. Considering mutations associated with high-level sulfadoxine-pyrimethamine resistance, prevalences of P. falciparum dihydrofolate reductase 164L (up to 80%) and dihydropteroate synthase 581G (up to 67%) were high at multiple sites. Considering P. falciparum kelch protein propeller domain mutations associated with artemisinin delayed clearance, prevalence of the 469Y and 675V mutations has increased at multiple sites in northern Uganda (up to 23% and 41%, respectively). Conclusions We demonstrate concerning spread of mutations that may limit efficacies of key antimalarial drugs.
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- 2020
14. Impact of Short-Term Storage on Ex Vivo Antimalarial Susceptibilities of Fresh Ugandan Plasmodium falciparum Isolates
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Martin Okitwi, Stephen Orena, Katairo Thomas, Patrick K. Tumwebaze, Oswald Byaruhanga, Samuel L. Nsobya, Melissa D. Conrad, Brett R. Bayles, Philip J. Rosenthal, and Roland A. Cooper
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Falciparum ,Pharmacology ,growth ,Plasmodium falciparum ,Drug Resistance ,malaria ,Pharmacology and Pharmaceutical Sciences ,Microbiology ,drug susceptibility ,antimalarials ,Vector-Borne Diseases ,Inhibitory Concentration 50 ,Orphan Drug ,Rare Diseases ,Good Health and Well Being ,Infectious Diseases ,cold storage ,Medical Microbiology ,parasitic diseases ,ex vivo ,Humans ,HIV/AIDS ,Uganda ,Pharmacology (medical) - Abstract
We measured susceptibilities of Ugandan Plasmodium falciparum isolates assayed on the day of collection or after storage at 4°C. Samples were incubated with serial dilutions of 8 antimalarials, and susceptibilities were determined from 72-h growth inhibition assays. Storage was associated with decreased growth and lower 50% inhibitory concentration values, but differences between assays beginning on day 0 or after 1 or 2 days of storage were modest, indicating that short-term storage before drug susceptibility determination is feasible.
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- 2022
15. Decreased Susceptibility to Dihydrofolate Reductase Inhibitors Associated With Genetic Polymorphisms in Ugandan Plasmodium falciparum Isolates
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Roland A. Cooper, Melissa D. Conrad, Oswald Byaruhanga, Ozkan Aydemir, Stephen Orena, Jeffrey A. Bailey, Patrick K Tumwebaze, Thomas Katairo, Philip J. Rosenthal, Sam L. Nsobya, Stephanie A Rasmussen, Jennifer Legac, Martin Okitwi, Oriana Kreutzfeld, and Maëlle Duffey
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Drug Resistance ,Drug resistance ,Medical and Health Sciences ,Dihydrofolate reductase ,Genotype ,Immunology and Allergy ,2.1 Biological and endogenous factors ,Uganda ,Malaria, Falciparum ,Aetiology ,biology ,antifolate resistance ,Biological Sciences ,Pyrimethamine ,Infectious Diseases ,Proguanil ,5.1 Pharmaceuticals ,PfDHFR ,Development of treatments and therapeutic interventions ,Infection ,medicine.drug ,Cycloguanil ,Falciparum ,Plasmodium falciparum ,malaria ,Microbiology ,Vaccine Related ,Major Articles and Brief Reports ,Antimalarials ,Rare Diseases ,Genetic ,parasitic diseases ,medicine ,Genetics ,Humans ,Polymorphism ,Polymorphism, Genetic ,Prevention ,medicine.disease ,biology.organism_classification ,Virology ,Vector-Borne Diseases ,Tetrahydrofolate Dehydrogenase ,Good Health and Well Being ,biology.protein ,Folic Acid Antagonists ,Malaria - Abstract
Background The Plasmodium falciparum dihydrofolate reductase (PfDHFR) inhibitors pyrimethamine and cycloguanil (the active metabolite of proguanil) have important roles in malaria chemoprevention, but drug resistance challenges their efficacies. A new compound, P218, was designed to overcome resistance, but drug-susceptibility data for P falciparum field isolates are limited. Methods We studied ex vivo PfDHFR inhibitor susceptibilities of 559 isolates from Tororo and Busia districts, Uganda, from 2016 to 2020, sequenced 383 isolates, and assessed associations between genotypes and drug-susceptibility phenotypes. Results Median half-maximal inhibitory concentrations (IC50s) were 42 100 nM for pyrimethamine, 1200 nM for cycloguanil, 13000 nM for proguanil, and 0.6 nM for P218. Among sequenced isolates, 3 PfDHFR mutations, 51I (100%), 59R (93.7%), and 108N (100%), were very common, as previously seen in Uganda, and another mutation, 164L (12.8%), had moderate prevalence. Increasing numbers of mutations were associated with decreasing susceptibility to pyrimethamine, cycloguanil, and P218, but not proguanil, which does not act directly against PfDHFR. Differences in P218 susceptibilities were modest, with median IC50s of 1.4 nM for parasites with mixed genotype at position 164 and 5.7 nM for pure quadruple mutant (51I/59R/108N/164L) parasites. Conclusions Resistance-mediating PfDHFR mutations were common in Ugandan isolates, but P218 retained excellent activity against mutant parasites.
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- 2022
16. Associations between Varied Susceptibilities to PfATP4 Inhibitors and Genotypes in Ugandan Plasmodium falciparum Isolates
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Jennifer Legac, Patrick K Tumwebaze, Stephen Orena, Roland A. Cooper, Maëlle Duffey, Aarti A. Ramanathan, Samuel L. Nsobya, Melissa D. Conrad, Martin Okitwi, Oriana Kreutzfeld, Philip J. Rosenthal, Oswald Byaruhanga, Ozkan Aydemir, Jeffrey A. Bailey, Stephanie A Rasmussen, Thomas Katairo, Victor Asua, Akhil B. Vaidya, and Brett R. Bayles
- Subjects
Nonsynonymous substitution ,Genotype ,Mutant ,Plasmodium falciparum ,Drug Resistance ,Protozoan Proteins ,Single-nucleotide polymorphism ,Drug resistance ,Biology ,medicine.disease_cause ,Microbiology ,Antimalarials ,Mechanisms of Resistance ,parasitic diseases ,medicine ,Humans ,Pharmacology (medical) ,Uganda ,Malaria, Falciparum ,Pharmacology ,Adenosine Triphosphatases ,Mutation ,medicine.disease ,biology.organism_classification ,Infectious Diseases ,Malaria - Abstract
Among novel compounds under recent investigation as potential new antimalarial drugs are three independently developed inhibitors of the Plasmodium falciparum P-type ATPase (PfATP4): KAE609 (cipargamin), PA92, and SJ733. We assessed ex vivo susceptibilities to these compounds of 374 fresh P. falciparum isolates collected in Tororo and Busia districts, Uganda, from 2016 to 2019. Median IC(50)s were 65 nM for SJ733, 9.1 nM for PA92, and 0.5 nM for KAE609. Sequencing of pfatp4 for 218 of these isolates demonstrated many nonsynonymous single nucleotide polymorphisms; the most frequent mutations were G1128R (69% of isolates mixed or mutant), Q1081K/R (68%), G223S (25%), N1045K (16%), and D1116G/N/Y (16%). The G223S mutation was associated with decreased susceptibility to SJ733, PA92, and KAE609. The D1116G/N/Y mutations were associated with decreased susceptibility to SJ733, and the presence of mutations at both codons 223 and 1116 was associated with decreased susceptibility to PA92 and SJ733. In all of these cases, absolute differences in susceptibilities of wild-type (WT) and mutant parasites were modest. Analysis of clones separated from mixed field isolates consistently identified mutant clones as less susceptible than WT. Analysis of isolates from other sites demonstrated the presence of the G223S and D1116G/N/Y mutations across Uganda. Our results indicate that malaria parasites circulating in Uganda have a number of polymorphisms in PfATP4 and that modestly decreased susceptibility to PfATP4 inhibitors is associated with some mutations now present in Ugandan parasites.
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- 2021
17. Sources of persistent malaria transmission in a setting with effective malaria control in eastern Uganda: a longitudinal, observational cohort study
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Lisette Meerstein-Kessel, Isabel Rodriguez-Barraquer, Chiara Andolina, Kjerstin Lanke, Philip J. Rosenthal, Moses R. Kamya, Joseph Okoth, Peter Olwoch, Teun Bousema, Bryan Greenhouse, Joaniter I. Nankabirwa, Melissa D. Conrad, Alex K. Musiime, Grant Dorsey, Jordache Ramjith, Jessica Briggs, John Rek, Chris Drakeley, Emmanuel Arinaitwe, Noam Teyssier, and Sarah G. Staedke
- Subjects
0301 basic medicine ,Male ,medicine.medical_specialty ,Adolescent ,Plasmodium falciparum ,Asymptomatic ,Cohort Studies ,03 medical and health sciences ,Antimalarials ,0302 clinical medicine ,All institutes and research themes of the Radboud University Medical Center ,Malaria transmission ,Internal medicine ,Anopheles ,parasitic diseases ,medicine ,Gametocyte ,Animals ,Humans ,Uganda ,030212 general & internal medicine ,Longitudinal Studies ,Malaria, Falciparum ,Child ,biology ,Transmission (medicine) ,business.industry ,Incidence (epidemiology) ,Artemether, Lumefantrine Drug Combination ,medicine.disease ,biology.organism_classification ,3. Good health ,Women's cancers Radboud Institute for Health Sciences [Radboudumc 17] ,030104 developmental biology ,Infectious Diseases ,lnfectious Diseases and Global Health Radboud Institute for Health Sciences [Radboudumc 4] ,Child, Preschool ,Female ,medicine.symptom ,business ,Malaria ,Cohort study - Abstract
BACKGROUND: Symptomatic malaria cases reflect only a small proportion of all Plasmodium spp infections. Many infected individuals are asymptomatic, and persistent asymptomatic Plasmodium falciparum infections are common in endemic settings. We aimed to quantify the contribution of symptomatic and asymptomatic infections to P falciparum transmission in Tororo, Uganda. METHODS: We did a longitudinal, observational cohort study in Tororo district, Uganda. We recruited participants of all ages from randomly selected households within this district. Participants were eligible if the selected household had no more than nine permanent residents and at least two members younger than 10 years, and the household was their primary residence, and they agreed to come to the study clinic for any fever episode and avoid antimalarial medications outside the study. Participants were followed-up by continuous passive surveillance for the incidence of symptomatic infections; routine assessments (ie, standardised clinical evaluation and blood samples) were done at baseline and at routine visits every 4 weeks for 2 years. P falciparum parasite density, gametocyte density, and genetic composition were determined molecularly using quantitative PCR (qPCR), quantitative reverse transcriptase PCR (qRT-PCR), and amplicon deep sequencing, respectively. Membrane feeding assays were also done to assess infectivity to mosquitoes. The contribution of different populations to the infectious reservoir was estimated for symptomatic infections, asymptomatic but microscopically detected infections, and asymptomatic but qPCR-detected infections; and for age groups younger than 5 years, 5-15 years, and 16 years or older. FINDINGS: Between Oct 4, 2017, and Oct 31, 2019, 531 individuals were enrolled from 80 randomly selected households and were followed-up for 2 years. At baseline, P falciparum was detected in 28 (5·3%) of 531 participants by microscopy and an additional 64 (12·1%) by qPCR and declined thereafter. In 538 mosquito feeding experiments on 107 individuals, 446 (1·2%) of 37 404 mosquitoes became infected, with mosquito infection rates being strongly associated with gametocyte densities (β=2·11, 95% CI 1·62-2·67; p
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- 2021
18. Balanced impacts of fitness and drug pressure on the evolution of PfMDR1 polymorphisms in Plasmodium falciparum
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Roland A. Cooper, Melissa D. Conrad, Jennifer Legac, Stephen Tukwasibwe, Marvin Duvalsaint, Patrick K Tumwebaze, and Philip J. Rosenthal
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0301 basic medicine ,Mutant ,RC955-962 ,PfMDR1 ,Drug resistance ,Infectious and parasitic diseases ,RC109-216 ,medicine.disease_cause ,Arctic medicine. Tropical medicine ,Fitness ,Genetics ,Mutation ,biology ,Chloroquine ,Infectious Diseases ,Medical Microbiology ,Quinolines ,Public Health and Health Services ,Multidrug Resistance-Associated Proteins ,Infection ,030106 microbiology ,Plasmodium falciparum ,Reversion ,Microbiology ,Vaccine Related ,03 medical and health sciences ,Antimalarials ,Rare Diseases ,Biodefense ,Tropical Medicine ,parasitic diseases ,medicine ,Lumefantrine ,Research ,Prevention ,Haplotype ,Wild type ,biology.organism_classification ,Malaria ,Vector-Borne Diseases ,030104 developmental biology ,Emerging Infectious Diseases ,Good Health and Well Being ,Parasitology ,Haplotypes ,Genetic Fitness ,Antimicrobial Resistance - Abstract
Background Anti-malarial drug resistance may be limited by decreased fitness in resistant parasites. Important contributors to resistance are mutations in the Plasmodium falciparum putative drug transporter PfMDR1. Methods Impacts on in vitro fitness of two common PfMDR1 polymorphisms, N86Y, which is associated with sensitivity to multiple drugs, and Y184F, which has no clear impact on drug sensitivity, were evaluated to study associations between resistance mediators and parasite fitness, measured as relative growth in competitive culture experiments. NF10 P. falciparum lines engineered to represent all PfMDR1 N86Y and Y184F haplotypes were co-cultured for 40 days, and the genetic make-up of the cultures was characterized every 4 days by pyrosequencing. The impacts of culture with anti-malarials on the growth of different haplotypes were also assessed. Lastly, the engineering of P. falciparum containing another common polymorphism, PfMDR1 D1246Y, was attempted. Results Co-culture results were as follows. With wild type (WT) Y184 fixed (N86/Y184 vs. 86Y/Y184), parasites WT and mutant at 86 were at equilibrium. With mutant 184 F fixed (N86/184F vs. 86Y/184F), mutants at 86 overgrew WT. With WT N86 fixed (N86/Y184 vs. N86/184F), WT at 184 overgrew mutants. With mutant 86Y fixed (86Y/Y184 vs. 86Y/184F), WT and mutant at 86 were at equilibrium. Parasites with the double WT were in equilibrium with the double mutant, but 86Y/Y184 overgrew N86/184F. Overall, WT N86/mutant 184F parasites were less fit than parasites with all other haplotypes. Parasites engineered for another mutation, PfMDR1 1246Y, were unstable in culture, with reversion to WT over time. Thus, the N86 WT is stable when accompanied by the Y184 WT, but incurs a fitness cost when accompanied by mutant 184F. Culturing in the presence of chloroquine favored 86Y mutant parasites and in the presence of lumefantrine favored N86 WT parasites; piperaquine had minimal impact. Conclusions These results are consistent with those for Ugandan field isolates, suggest reasons for varied haplotypes, and highlight the interplay between drug pressure and fitness that is guiding the evolution of resistance-mediating haplotypes in P. falciparum.
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- 2021
19. Persistent malaria transmission from asymptomatic children despite highly effective malaria control in eastern Uganda
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Chris Drakeley, Grant Dorsey, Chiara Andolina, Joseph Okoth, Sarah G. Staedke, Emmanuel Arinaitwe, Moses R. Kamya, Kjerstin Lanke, Bryan Greenhouse, Peter Olwoch, Teun Bousema, P. Rosenthal, Joaniter I. Nankabirwa, Alex K. Musiime, Melissa D. Conrad, Isabel Rodriguez-Barraquer, Lisette Meerstein-Kessel, Ramjith J, Noam Teyssier, John Rek, and Jessica Briggs
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Pediatrics ,medicine.medical_specialty ,biology ,Transmission (medicine) ,business.industry ,Plasmodium falciparum ,biology.organism_classification ,medicine.disease ,Asymptomatic ,Malaria transmission ,Cohort ,Gametocyte ,medicine ,medicine.symptom ,Malaria control ,business ,Malaria - Abstract
SummaryBackgroundPersistent asymptomaticPlasmodium falciparuminfections are common in malaria-endemic settings, but their contribution to transmission is poorly understood.MethodsA cohort of children and adults from Tororo, Uganda was closely followed for 24 months by continuous passive surveillance and routine assessments.P. falciparumparasite density, gametocyte density and genetic composition were determined molecularly; mosquito membrane feeding assays were performed on samples from participants with symptomatic and asymptomatic infections.FindingsFrom October 2017 to October 2019, we followed all 531 residents from 80 households. Parasite prevalence was 5·8% by microscopy and 17·3% by PCR at enrolment and declined thereafter. We conducted 538 mosquito feeding experiments on samples from 107 individuals. Mosquito infection rates were strongly associated with gametocyte densities of participants. Considering both transmissibility of infections and their relative frequency, the estimated human infectious reservoir was primarily asymptomatic microscopy-detected infections (83·8%), followed by asymptomatic submicroscopic (15·6%) and symptomatic (0·6%) infections. Over half of the infectious reservoir was children aged 5-15 years (56·8%); individuals >16 years (15·7%) contributed less. Four children were responsible for 62·6% (279/446) of infected mosquitos and were infectious at multiple timepoints.InterpretationIndividuals with asymptomatic infections were important drivers of malaria transmission. School-aged children were responsible for over half of all mosquito infections, with a small minority of asymptomatic children highly infectious. Demographically targeted interventions, aimed at school-aged children, could further reduce transmission in areas under effective vector control.FundingNational institute of Health, Bill & Melinda Gates Foundation, European Research Council.
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- 2021
20. Antimalarial drug resistance in Africa: the calm before the storm?
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Philip J. Rosenthal and Melissa D. Conrad
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0301 basic medicine ,medicine.medical_specialty ,Combination therapy ,Plasmodium falciparum ,030106 microbiology ,030231 tropical medicine ,Drug resistance ,Antimalarials ,03 medical and health sciences ,0302 clinical medicine ,Pharmacotherapy ,Chloroquine ,parasitic diseases ,medicine ,Humans ,Malaria, Falciparum ,Artemisinin ,Child ,Intensive care medicine ,Africa South of the Sahara ,Resistance (ecology) ,biology ,business.industry ,Incidence ,Drug Resistance, Microbial ,medicine.disease ,biology.organism_classification ,Artemisinins ,Treatment Outcome ,Infectious Diseases ,Drug Therapy, Combination ,business ,Malaria ,medicine.drug - Abstract
Antimalarial drug resistance, in particular resistance to Plasmodium falciparum, challenges the treatment and control of malaria. In this Review, we summarise evolving patterns of antimalarial drug resistance in Africa. Resistance to aminoquinolines and antifolates is long-standing, yet with greatly decreased use of chloroquine to treat malaria, the prevalence of resistance to chloroquine has decreased. Resistance to antifolates, which are used to prevent malaria in some settings, remains widespread. Resistance to artemisinin-based combination therapies, the standard treatments for malaria in Africa, has emerged in southeast Asia. At present, resistance to artemisinins or key partner drugs included in combination therapies does not appear to be a substantial problem in Africa. However, emergence of resistance to artemisinin-based combination therapies in Africa would probably have devastating consequences, and continued surveillance for the emergence of resistance on this continent is a high priority.
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- 2019
21. Comparative Efficacy of Artemether-Lumefantrine and Dihydroartemisinin-Piperaquine for the Treatment of Uncomplicated Malaria in Ugandan Children
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Erika Wallender, Ruth Kigozi, Philip J. Rosenthal, Ronald Mulebeke, Joseph Senzoga, Agaba B. Bosco, Simeon Kalyesubula, Adoke Yeka, Melissa D. Conrad, Paul Kyambadde, Jimmy Opigo, Afizi Kibuuka, and Joanna Vinden
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Male ,0301 basic medicine ,Comparative Effectiveness Research ,medicine.medical_specialty ,Artemether/lumefantrine ,Genotype ,Plasmodium falciparum ,Drug Resistance ,Protozoan Proteins ,Parasitemia ,Drug resistance ,Antimalarials ,Major Articles and Brief Reports ,03 medical and health sciences ,0302 clinical medicine ,Dihydroartemisinin/piperaquine ,Recurrence ,Internal medicine ,Piperaquine ,parasitic diseases ,medicine ,Humans ,Immunology and Allergy ,Single-Blind Method ,Uganda ,030212 general & internal medicine ,Malaria, Falciparum ,biology ,business.industry ,Artemether, Lumefantrine Drug Combination ,Infant ,Membrane Transport Proteins ,medicine.disease ,biology.organism_classification ,Artemisinins ,Drug Combinations ,Regimen ,030104 developmental biology ,Infectious Diseases ,Child, Preschool ,Quinolines ,Female ,Multidrug Resistance-Associated Proteins ,business ,Malaria ,medicine.drug - Abstract
Background In Uganda, artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DHA-PQ) showed excellent treatment efficacy for uncomplicated malaria in prior trials. Because the frequency of resistance to artemisinins and piperaquine is increasing in Southeast Asia and the prevalence of Plasmodium falciparum polymorphisms associated with resistance has changed, we reassessed treatment efficacies at 3 sites in Uganda. Methods For this randomized, single-blinded clinical trial, children aged 6–59 months with uncomplicated falciparum malaria were assigned treatment with AL or DHA-PQ and followed for 42 days. Primary end points were risks of recurrent parasitemia, either unadjusted or adjusted to distinguish recrudescence from new infection. We assessed selection by study regimens of relevant P. falciparum genetic polymorphisms associated with drug resistance. Results Of 599 patients enrolled, 578 completed follow-up. There were no early treatment failures. The risk of recurrent parasitemia was lower with DHA-PQ as compared to AL at all 3 sites at 42 days (26.0% vs 47.0%; P < .001). Recrudescent infections were uncommon in both the DHA-PQ and AL arms (1.1% and 2.2%, respectively; P = .25). Neither regimen selected for pfcrt or pfmdr1 polymorphisms associated with drug resistance. Conclusions AL and DHA-PQ remain effective for the treatment of malaria in Uganda. Neither regimen selected for genetic polymorphisms associated with drug resistance. Clinical Trials Registration ISRCTN15793046.
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- 2018
22. Deletions of pfhrp2 and pfhrp3 genes were uncommon in rapid diagnostic test-negative Plasmodium falciparum isolates from Uganda
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Andrew Walakira, Emmanuel Ruhamyankaka, Joaniter I. Nankabirwa, Emmanuel Arinaitwe, Melissa D. Conrad, Philip J. Rosenthal, Elizabeth Namirembe, Moses Kiggundu, Moses R. Kamya, Sam L. Nsobya, and Grant Dorsey
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Protozoan Proteins ,pfhrp3 ,Rapid diagnostic test ,pfhrp2 ,law.invention ,law ,Uganda ,Child ,Polymerase chain reaction ,biology ,medicine.diagnostic_test ,Infectious Diseases ,Medical Microbiology ,Child, Preschool ,Protozoan ,Public Health and Health Services ,Infection ,lcsh:Arctic medicine. Tropical medicine ,Adolescent ,lcsh:RC955-962 ,Plasmodium falciparum ,HRP2 ,Antigens, Protozoan ,Microbiology ,lcsh:Infectious and parasitic diseases ,Rare Diseases ,Diagnostic Tests ,Clinical Research ,Tropical Medicine ,parasitic diseases ,Genetics ,medicine ,Humans ,lcsh:RC109-216 ,Routine ,Antigens ,Preschool ,Gene ,Ribosomal DNA ,Diagnostic Tests, Routine ,Research ,Infant ,biology.organism_classification ,medicine.disease ,Virology ,Malaria ,Vector-Borne Diseases ,Good Health and Well Being ,Cross-Sectional Studies ,Parasitology ,Immunoassay ,Gene Deletion - Abstract
Background Rapid diagnostic tests (RDTs) play a key role in malaria case management. The most widely used RDT identifies Plasmodium falciparum based on immunochromatographic recognition of P. falciparum histidine-rich protein 2 (PfHRP2). Deletion of the paralogous pfhrp2 and pfhrp3 genes leads to false-negative PfHRP2-based RDTs, and has been reported in P. falciparum infections from South America and Africa. However, identification of pfhrp2/pfhrp3 deletions has usually been based only on failure to amplify these genes using PCR, without confirmation based on PfHRP2 protein expression, and understanding of the true prevalence of deletions is incomplete. Methods Deletions of pfhrp2/pfhrp3 in blood samples were investigated from cross-sectional surveys in 2012-13 in three regions of varied malaria transmission intensity in Uganda. Samples with positive Giemsa-stained thick blood smears, but negative PfHRP2-based RDTs were evaluated by PCR amplification of conserved subunit ribosomal DNA for Plasmodium species, PCR amplification of pfhrp2 and pfhrp3 genes to identify deletions, and bead-based immunoassays for expression of PfHRP2. Results Of 3516 samples collected in cross-sectional surveys, 1493 (42.5%) had positive blood smears, of which 96 (6.4%) were RDT-negative. Of these 96 RDT-negative samples, P. falciparum DNA was identified by PCR in 56 (58%) and only non-falciparum plasmodial DNA in 40 (42%). In all 56 P. falciparum-positive samples there was a failure to amplify pfhrp2 or pfhrp3: in 25 (45%) pfhrp2 was not amplified, in 39 (70%) pfhrp3 was not amplified, and in 19 (34%) neither gene was amplified. For the 39 P. falciparum-positive, RDT-negative samples available for analysis of protein expression, PfHRP2 was not identified by immunoassay in only four samples (10.3%); these four samples all had failure to amplify both pfhrp2 and pfhrp3 by PCR. Thus, only four of 96 (4.2%) smear-positive, RDT-negative samples had P. falciparum infections with deletion of pfhrp2 and pfhrp3 confirmed by failure to amplify the genes by PCR and lack of expression of PfHRP2 demonstrated by immunoassay. Conclusion False negative RDTs were uncommon. Deletions in pfhrp2 and pfhrp3 explained some of these false negatives, but most false negatives were not due to deletion of the pfhrp2 and pfhrp3 genes.
- Published
- 2021
23. Deletions of pfhrp2 and pfhrp3 genes were uncommon in rapid diagnostic test-negative Plasmodium falciparum isolates from Uganda
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Sam L Nsobya, Andrew Walakira, Elizabeth Namirembe, Moses Kiggundu, Joaniter I Nankabirwa, Emmanuel Ruhamyankaka, Emmanuel Arinaitwe, Melissa D Conrad, Moses R Kamya, Grant Dorsey, and Philip J Rosenthal
- Subjects
parasitic diseases - Abstract
BackgroundRapid diagnostic tests (RDTs) play a key role in malaria case management. The most widely used RDT identifies Plasmodium falciparum based on immunochromatographic recognition of P. falciparum histidine-rich protein 2 (PfHRP2). Deletion of the paralogous pfhrp2 and pfhrp3 genes leads to false-negative PfHRP2-based RDTs, and has been reported in P. falciparum infections from South America and Africa. However, identification of pfhrp2/pfhrp3 deletions has usually been based only on failure to amplify these genes using PCR, without confirmation based on PfHRP2 protein expression, and understanding of the true prevalence of deletions is incomplete.MethodsDeletions of pfhrp2/pfhrp3 in blood samples were investigated from cross-sectional surveys in 2012-13 in three regions of varied malaria transmission intensity in Uganda. Samples with positive Giemsa-stained thick blood smears, but negative PfHRP2-based RDTs were evaluated by PCR amplification of conserved subunit ribosomal DNA for Plasmodium species, PCR amplification of pfhrp2 and pfhrp3 genes to identify deletions, and bead-based immunoassays for expression of PfHRP2.ResultsOf 3516 samples collected in cross-sectional surveys, 1493 (42.5%) had positive blood smears, of which 96 (6.4%) were RDT-negative. Of these 96 RDT-negative samples, P. falciparum DNA was identified by PCR in 56 (58%) and only non-falciparum plasmodial DNA in 40 (42%). In all 56 P. falciparum-positive samples there was a failure to amplify pfhrp2 or pfhrp3: in 25 (45%) pfhrp2 was not amplified, in 39 (70%) pfhrp3 was not amplified, and in 19 (34%) neither gene was amplified. For the 39 P. falciparum-positive, RDT-negative samples available for analysis of protein expression, PfHRP2 was not identified by immunoassay in only four samples (10.3%); these four samples all had failure to amplify both pfhrp2 and pfhrp3 by PCR. Thus, only four of 96 (4.2%) smear-positive, RDT-negative samples had P. falciparum infections with deletion of pfhrp2 and pfhrp3 confirmed by failure to amplify the genes by PCR and lack of expression of PfHRP2 demonstrated by immunoassay.ConclusionFalse negative RDTs were uncommon. Deletions in pfhrp2 and pfhrp3 explained some of these false negatives, but most false negatives were not due to deletion of the pfhrp2 and pfhrp3 genes.
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- 2020
24. Associations between Malaria-Preventive Regimens and Plasmodium falciparum Drug Resistance-Mediating Polymorphisms in Ugandan Pregnant Women
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Richard Kajubi, Victor Asua, Moses R. Kamya, Philip J. Rosenthal, Melissa D. Conrad, Dennis Muhanguzi, Patience Nayebare, Abel Kakuru, Grant Dorsey, Sam L. Nsobya, and Joaniter I. Nankabirwa
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Drug Resistance ,Drug resistance ,chemistry.chemical_compound ,0302 clinical medicine ,Dihydroartemisinin/piperaquine ,Pregnancy ,Medicine ,Pharmacology (medical) ,Uganda ,030212 general & internal medicine ,Malaria, Falciparum ,0303 health sciences ,biology ,dihydroartemisinin-piperaquine ,Pharmacology and Pharmaceutical Sciences ,Drug Combinations ,Infectious Diseases ,Pyrimethamine ,Medical Microbiology ,Antifolate ,HIV/AIDS ,Female ,Infection ,medicine.drug ,Falciparum ,medicine.medical_specialty ,Clinical Trials and Supportive Activities ,Plasmodium falciparum ,malaria ,Microbiology ,03 medical and health sciences ,Antimalarials ,Rare Diseases ,Genetic ,Clinical Research ,Mechanisms of Resistance ,Internal medicine ,parasitic diseases ,Sulfadoxine ,Genetics ,Humans ,Polymorphism ,Pharmacology ,Intermittent preventive therapy ,Polymorphism, Genetic ,030306 microbiology ,business.industry ,Prevention ,medicine.disease ,biology.organism_classification ,Sulfadoxine/pyrimethamine ,sulfadoxine-pyrimethamine ,Malaria ,Vector-Borne Diseases ,Orphan Drug ,Good Health and Well Being ,chemistry ,intermittent preventive therapy ,Pregnant Women ,business - Abstract
Intermittent preventive treatment in pregnancy (IPTp) with monthly sulfadoxine-pyrimethamine (SP) is recommended for malaria-endemic parts of Africa, but efficacy is compromised by resistance, and, in recent trials, dihydroartemisinin-piperaquine (DP) has shown better antimalarial protective efficacy. We utilized blood samples from a recent trial to evaluate selection by IPTp with DP or SP of Plasmodium falciparum genetic polymorphisms that alter susceptibility to these drugs. The prevalence of known genetic polymorphisms associated with altered drug susceptibility was determined in parasitemic samples, including 375 collected before IPTp drugs were administered, 125 randomly selected from those receiving SP, and 80 from those receiving DP. For women receiving DP, the prevalence of mixed/mutant sequences was greater in samples collected during IPTp than that in samples collected prior to the intervention for PfMDR1 N86Y (20.3% versus 3.9%; P
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- 2020
25. Deletions of pfhrp2 and pfhrp3 genes in rapid diagnostic test-negative Plasmodium falciparum isolates from Uganda
- Author
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Joaniter I. Nankabirwa, Emmanuel Ruhamyankaka, Grant Dorsey, Philip J. Rosenthal, Andrew Walakira, Elizabeth Namirembe, Sam L. Nsobya, Emmanuel Arinaitwe, Moses Kiggundu, Moses R. Kamya, and Melissa D. Conrad
- Subjects
Rapid diagnostic test ,parasitic diseases ,Plasmodium falciparum ,Biology ,biology.organism_classification ,Gene ,Virology - Abstract
Background: Rapid diagnostic tests (RDTs) play a key role in malaria case management. The most widely used RDT identifies Plasmodium falciparum based on immunochromatographic recognition of P. falciparum histidine-rich protein 2 (PfHRP2). Deletion of the homologous pfhrp2 and pfhrp3 genes leads to false-negative PfHRP2-based RDTs, and has been reported in P. falciparum from South America and Africa. However, identification of pfhrp2/pfhrp3 deletions has usually been based only on failure to amplify these genes using PCR, without confirmation based on protein expression, and our understanding of the true prevalence of deletions is incomplete. Methods: We investigated pfhrp2 / pfhrp3 deletions in blood samples from cross-sectional surveys in 2012-13 in three regions of varied malaria transmission intensity in Uganda. We evaluated samples with positive Giemsa-stained thick blood smears and negative PfHRP2-based RDTs by PCR amplification of conserved subunit ribosomal DNA for Plasmodium species, PCR amplification of pfhrp2 and pfhrp3 genes to identify deletions, and bead-based immunoassays for expression ofPfHRP2. Results: Of 3516 samples collected in cross-sectional surveys, 1493 (42.5%) had positive blood smears, of which 96 (6.4%) were RDT-negative. Of these 96 RDT-negative samples, P. falciparum was identified in 56 (58%) and only non-falciparum plasmodial DNA in 40 (42%). In all 56 P. falciparum -positive samples there was a failure to amplify pfhrp2 or pfhrp3 :in 25 (45%) pfhrp2 was not amplified, in 39 (70%) pfhrp3 was not amplified, and in 19 (34%) neither gene was amplified. For the 39 P. falciparum -positive, RDT-negative samples available for analysis of protein expression, PfHRP2 was not identified by immunoassay in only four samples (10.3%); these four samples all had failure to amplify both pfhrp2 and pfhrp3 by PCR. Thus, only four of 96 (4.2%) smear-positive, RDT-negative samples had P. falciparum infections with deletion of pfhrp2 and pfhrp3 confirmed by failure to amplify the genes by PCR and lack of expression of PfHRP2 demonstrated by immunoassay. Conclusion: False negative RDTs were uncommon, and deletions in pfhrp2 and pfhrp3 explained some of these findings, although most false negatives were not due to deletion of the pfhrp2 and pfhrp3 genes.
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- 2020
26. Identification and characterization of immature Anopheles and culicines (Diptera: Culicidae) at three sites of varying malaria transmission intensities in Uganda
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David L. Smith, Moses R. Kamya, Chris Drakeley, Melissa D. Conrad, Maxwell Kilama, Emmanuel Arinaitwe, Joaniter I. Nankabirwa, Alex K. Musiime, Grant Dorsey, Steve W. Lindsay, Patrick Kyagamba, Sarah G. Staedke, John Rek, Otto Geoffrey, and Anne M. Akol
- Subjects
Veterinary medicine ,lcsh:Arctic medicine. Tropical medicine ,lcsh:RC955-962 ,030231 tropical medicine ,Indoor residual spraying ,Mosquito Vectors ,Aquatic habitats ,lcsh:Infectious and parasitic diseases ,law.invention ,03 medical and health sciences ,Larvae ,0302 clinical medicine ,law ,Anopheles ,parasitic diseases ,medicine ,Animals ,Uganda ,lcsh:RC109-216 ,030212 general & internal medicine ,Ecosystem ,Larva ,biology ,Research ,fungi ,Pupa ,Pupae ,biology.organism_classification ,medicine.disease ,Malaria ,Culicine ,Culicidae ,Infectious Diseases ,Transmission (mechanics) ,Parasitology ,Anopheline ,Paddy field ,Animal Distribution - Abstract
Background Over the last two decades, there has been remarkable progress in malaria control in sub-Saharan Africa, due mainly to the massive deployment of long-lasting insecticidal nets and indoor residual spraying. Despite these gains, it is clear that in many situations, additional interventions are needed to further reduce malaria transmission. The World Health Organization (WHO) has promoted the Integrated Vector Management (IVM) approach through its Global Vector Control Response 2017–2030. However, prior roll-out of larval source management (LSM) as part of IVM, knowledge on ecology of larval aquatic habitats is required. Methods Aquatic habitats colonized by immature Anopheles and culicines vectors were characterized at three sites of low, medium and high malaria transmission in Uganda from October 2011 to June 2015. Larval surveys were conducted along transects in each site and aquatic habitats described according to type and size. Immature Anopheles, culicines and pupae from the described habitats were sampled using standard dipping methods to determine larval and pupae densities. Larvae were identified as anopheline or culicine, and counted. Pupae were not identified further. Binary logistic regression analysis was used to identify factors associated with the presence of immature Anopheles and culicines in each site. Results A total of 1205 larval aquatic habitats were surveyed and yielded a total of 17,028 anopheline larvae, 26,958 culicine larvae and 1189 pupae. Peaks in larval abundance occurred in all sites in March–May and August-October coinciding with the rainy seasons. Anopheles larvae were found in 52.4% (n = 251) of aquatic habitats in Tororo, a site of high transmission, 41.9% (n = 536) of habitats in Kanungu, a site with moderate malaria transmission, and 15.8% (n = 418) in Jinja, a site with low malaria transmission. The odds of finding larvae was highest in rice fields compared to pools in both Tororo (odds ratio, OR = 4.21, 95% CI 1.22–14.56, p = 0.02) and Kanungu (OR = 2.14, 95% CI 1.12–4.07, p = 0.02), while in Jinja the odd were highest in containers (OR = 4.55, 95% CI = 1.09–19.14, p = 0.03). In Kanungu, larvae were less likely to be found in containers compared to pools (OR = 0.26, 95% CI 0.09–0.66, p = 0.008) and river fringe (OR = 0.19, 95% CI 0.07–0.52, p = 0.001). Medium sized habitats were associated with high odds of finding larvae compared to small habitats (OR = 3.59, 95% CI 1.18–14.19, p = 0.039). Conclusions These findings show that immature Anopheles and culicines were common in areas of high and moderate transmission but were rare in areas of low transmission. Although immature Anopheles and culicines were found in all types of water bodies, they were most common in rice fields and less common in open drains and in river fringes. Methods are needed to reduce the aquatic stages of anopheline mosquitoes in human-made habitats, particularly rice fields.
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- 2020
27. Identification and characterization of Anopheles larval aquatic habitats at three sites of varying malaria transmission intensities in Uganda
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John Rek, Grant Dorsey, David L. Smith, Melissa D. Conrad, Chris Drakeley, Geoffrey Otto, Anne M. Akol, Steve W. Lindsay, Sarah G. Staedke, Emmanuel Arinaitwe, Moses R. Kamya, Maxwell Kilama, Joaniter I. Nankabirwa, Alex K. Musiime, and Patrick Kyagamba
- Subjects
Larva ,Malaria transmission ,Aquatic ecosystem ,parasitic diseases ,fungi ,Anopheles ,Zoology ,Identification (biology) ,Biology ,biology.organism_classification - Abstract
Background: Over the last two decades, there has been remarkable progress in malaria control in sub-Saharan Africa, due mainly to the massive deployment of long-lasting insecticidal nets and indoor residual spraying. Despite these gains, it is clear that in many situations, additional interventions are needed to further reduce malaria transmission. Larval source management (LSM) is a potential supplementary measure that could be used to control malaria. However, prior to its roll-out, knowledge on ecology of larval aquatic habitats is required.Methods: Aquatic habitats colonized by Anopheles vectors were characterised at three sites of low, medium and high malaria transmission in Uganda from October 2011 to June 2016. Larval surveys were conducted along transects in each site and aquatic habitats described according to type and size. Anopheles mosquito larvae and pupae from the described habitats were sampled using standard dipping methods to determine larval densities. Larvae were identified as anopheline or culicine and counted. Pupae were not identified further. Binary logistic regression analysis was used to identify factors associated with the presence of Anopheles larvae in each site.Results: A total of 1,205 larval aquatic habitats were surveyed and yielded a total of 17,028 anopheline larvae, 26,958 culicine larvae and 1,189 pupae. Peaks in larval abundance occurred in all sites in March-May and August-October coinciding with the rainy seasons. Anopheles larvae were found in 52.4 % (n = 251) of aquatic habitats in Tororo, a site of high transmission, 41.9 % (n = 536) of habitats in Kanungu, a site with moderate malaria transmission, and 15.8 % (n=418) in Jinja, a site with low malaria transmission. The odds of finding Anopheles larvae was highest in rice fields compared to pools in both Tororo (odds ratio, OR = 4.21, 95% CI 1.22-14.56, p = 0.02) and Kanungu (OR= 2.14, 95% CI 1.12-4.07, p =0.02). In Kanungu, Anopheles larvae were less likely to be found in open drains compared to pools (OR = 0.15, 95% CI 0.03-0.72, p = 0.02) and river fringe (OR = 0.19, 95% CI 0.07-0.52, p = 0.001). Conclusions: These findings show that Anopheles larvae were common in areas of high and moderate transmission but were rare in areas of low transmission. Although Anopheles larvae were found in all types of water bodies, they were most common in rice fields and less common in open drains and on river fringes. Methods are needed to reduce the aquatic stages of anopheline mosquitoes in human-made habitats, particularly rice fields.
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- 2020
28. Persistent Malaria Transmission from Asymptomatic Children Despite Highly Effective Malaria Control in Eastern Uganda
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Noam Teyssier, Lisette Meerstein-Kessel, Chiara Andolina, Sarah G. Staedke, Melissa D. Conrad, Grant Dorsey, Jessica Briggs, Jordache Ramjith, Moses R. Kamya, Peter Olwoch, Philip J. Rosenthal, Bryan Greenhouse, Kjerstin Lanke, John Rek, Alex K. Musiime, Joaniter I. Nankabirwa, Isabel Rodriguez-Barraquer, Joseph Okoth, Teun Bousema, and Chris Drakeley
- Subjects
medicine.medical_specialty ,biology ,Transmission (medicine) ,business.industry ,Indoor residual spraying ,Anopheles ,medicine.disease ,biology.organism_classification ,Asymptomatic ,Environmental health ,parasitic diseases ,Tropical medicine ,Cohort ,medicine ,Gametocyte ,medicine.symptom ,business ,Malaria - Abstract
Background: Persistent asymptomatic Plasmodium falciparum infections are common in malaria- endemic settings, but their contribution to transmission is poorly understood. Methods: A cohort of children and adults from Tororo, Uganda was closely followed for 24 months by continuous passive surveillance and routine assessments. P. falciparum parasite density, gametocyte density and genetic composition were determined molecularly; mosquito membrane feeding assays were performed on samples from participants with symptomatic and asymptomatic infections. Findings: From October 2017 to October 2019, we followed all 531 residents from 80 households. Parasite prevalence was 5·8% by microscopy and 17·3% by PCR at enrolment and declined thereafter. We conducted 538 mosquito feeding experiments on samples from 107 individuals. Mosquito infection rates were strongly associated with gametocyte densities of participants. Considering both transmissibility of infections and their relative frequency, the estimated human infectious reservoir was primarily asymptomatic microscopy-detected infections (83·8%), followed by asymptomatic submicroscopic (15·6%) and symptomatic (0·6%) infections. Over half of the infectious reservoir was children aged 5-15 years (56·8%); individuals 16 years (15·7%) contributed less. Four children were responsible for 62·6% (279/446) of infected mosquitos and were infectious at multiple timepoints. Interpretation: Individuals with asymptomatic infections were important drivers of malaria transmission. School-aged children were responsible for over half of all mosquito infections, with a small minority of asymptomatic children highly infectious. Demographically targeted interventions, aimed at school-aged children, could further reduce transmission in areas under effective vector control. Funding Statement: National institute of Health, Bill & Melinda Gates Foundation, European Research Council. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: Ethical approval for the study was received from the Uganda National Council of Science and Technology (HS119ES), Makerere University School of Medicine, the University of California, San Francisco and the London School of Hygiene & Tropical Medicine.
- Published
- 2020
29. Impact of vector control interventions on malaria transmission intensity, outdoor vector biting rates and Anopheles mosquito species composition in Tororo, Uganda
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Emmanuel Arinaitwe, Sarah G. Staedke, Moses R. Kamya, Melissa D. Conrad, John Rek, Alex K. Musiime, Grant Dorsey, Steve W. Lindsay, David L. Smith, J.P. Egonyu, Anne M. Akol, Joaniter I. Nankabirwa, and Maxwell Kilama
- Subjects
Veterinary medicine ,medicine.medical_specialty ,Mosquito Control ,lcsh:Arctic medicine. Tropical medicine ,lcsh:RC955-962 ,Anopheles gambiae ,030231 tropical medicine ,Indoor residual spraying ,Mosquito Vectors ,lcsh:Infectious and parasitic diseases ,law.invention ,03 medical and health sciences ,0302 clinical medicine ,law ,Anopheles ,parasitic diseases ,medicine ,Animals ,Transmission ,Uganda ,lcsh:RC109-216 ,030212 general & internal medicine ,2. Zero hunger ,biology ,Research ,Long-lasting insecticide nets ,Biting rates ,Insect Bites and Stings ,Plasmodium falciparum ,Biodiversity ,biology.organism_classification ,medicine.disease ,Malaria ,3. Good health ,Infectious Diseases ,Transmission (mechanics) ,Malaria vector ,Vector (epidemiology) ,Tropical medicine ,Female ,Parasitology - Abstract
Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are widely recommended for the prevention of malaria in endemic regions. Data from human landing catches provide information on the impact of vector control on vector populations. Here, malaria transmission indoors and outdoors, before and after mass deployment of LLINs and IRS in Uganda was compared. Methods The study took place in Tororo district, a historically high transmission area where universal LLIN distribution was conducted in November 2013 and May 2017 and 6 rounds of IRS implemented from December 2014 to July 2018. Human landing catches were performed in 8 houses monthly from October 2011 to September 2012 (pre-intervention period) and every 4 weeks from November 2017 to October 2018 (post-intervention period). Mosquitoes were collected outdoors from 18:00 to 22:00 h and indoors from 18:00 to 06:00 h. Female Anopheles were tested for the presence of Plasmodium falciparum sporozoites and species identification performed using gross dissection and polymerase chain reaction (PCR). Results The interventions were associated with a decline in human biting rate from 19.6 to 2.3 female Anopheles mosquitoes per house per night (p Anopheles gambiae sensu stricto (s.s.), which comprised an estimated 76.7% of mosquitoes. Following the interventions, the predominant species was Anopheles arabiensis, which comprised 99.5% of mosquitoes, with almost complete elimination of An. gambiae s.s. (0.5%). Conclusions Mass distribution of LLINs and 6 rounds of IRS dramatically decreased vector density and sporozoite rate resulting in a marked reduction in malaria transmission intensity in a historically high transmission site in Uganda. These changes were accompanied by a shift in vector species from An. gambiae s.s. to An. arabiensis and a relative increase in outdoor biting.
- Published
- 2019
30. Comparative Prevalence of Plasmodium falciparum Resistance-Associated Genetic Polymorphisms in Parasites Infecting Humans and Mosquitoes in Uganda
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Maxwell Kilama, Moses R. Kamya, Philip J. Rosenthal, Grant Dorsey, Alex K. Musiime, Melissa D. Conrad, John Rek, and Daniel Mota
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0301 basic medicine ,Genetics ,biology ,Directional selection ,Anopheles gambiae ,030106 microbiology ,Plasmodium falciparum ,Drug resistance ,medicine.disease ,biology.organism_classification ,Virology ,03 medical and health sciences ,Infectious Diseases ,parasitic diseases ,Genotype ,medicine ,Parasitology ,Allele ,Gene ,Malaria - Abstract
Controlling malaria in high transmission areas, such as much of sub-Saharan Africa, will require concerted efforts to slow the spread of drug resistance and to impede malaria transmission. Understanding the fitness costs associated with the development of drug resistance, particularly within the context of transmission, can help guide policy decisions to accomplish these goals, as fitness constraints might lead to decreased transmission of drug-resistant strains. To determine if Plasmodium falciparum resistance-mediating polymorphisms impact on development at different parasite stages, we compared the genotypes of parasites infecting humans and mosquitoes from households in Uganda. Genotypes at 14 polymorphic loci in genes encoding putative transporters (pfcrt and pfmdr1) and folate pathway enzymes (pfdhfr and pfdhps) were characterized using ligase detection reaction-fluorescent microsphere assays. In paired analysis using the Wilcoxon signed-rank test, prevalences of mutations at 12 loci did not differ significantly between parasites infecting humans and mosquitoes. However, compared with parasites infecting humans, those infecting mosquitoes were enriched for the pfmdr1 86Y mutant allele (P = 0.0001) and those infecting Anopheles gambiae s.s. were enriched for the pfmdr1 86Y (P = 0.0001) and pfcrt 76T (P = 0.0412) mutant alleles. Our results suggest modest directional selection resulting from varied fitness costs during the P. falciparum life cycle. Better appreciation of the fitness implications of drug resistance mediating mutations can inform optimal malaria treatment and prevention strategies.
- Published
- 2017
31. Impact of Intermittent Preventive Treatment During Pregnancy on Plasmodium falciparum Drug Resistance–Mediating Polymorphisms in Uganda
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Melissa D. Conrad, Francesca T. Aweeka, Liusheng Huang, Moses R. Kamya, Daniel Mota, Marissa Foster, Meghan Whalen, Grant Dorsey, Philip J. Rosenthal, Patrick K Tumwebaze, Diane V. Havlir, Erika Wallender, Stephen Tukwasibwe, Patience Nayebare, Prasanna Jagannathan, Abel Kakuru, and Jennifer Legac
- Subjects
IPT ,0301 basic medicine ,Drug Resistance ,Drug resistance ,Medical and Health Sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Dihydroartemisinin/piperaquine ,Pregnancy ,2.1 Biological and endogenous factors ,Immunology and Allergy ,Aetiology ,Malaria, Falciparum ,biology ,dihydroartemisinin-piperaquine ,Biological Sciences ,Artemisinins ,Drug Combinations ,Pyrimethamine ,Infectious Diseases ,Antifolate ,Quinolines ,HIV/AIDS ,Female ,Infection ,medicine.drug ,Falciparum ,Plasmodium falciparum ,030231 tropical medicine ,030106 microbiology ,P. falciparum ,Microbiology ,Major Articles and Brief Reports ,Antimalarials ,03 medical and health sciences ,Rare Diseases ,Genetic ,Piperaquine ,Sulfadoxine ,parasitic diseases ,Genetics ,medicine ,Humans ,Polymorphism ,Polymorphism, Genetic ,business.industry ,Prevention ,Haplotype ,medicine.disease ,biology.organism_classification ,Sulfadoxine/pyrimethamine ,Malaria ,sulfadoxine-pyrimethamine ,Vector-Borne Diseases ,Good Health and Well Being ,chemistry ,Immunology ,Antimicrobial Resistance ,business - Abstract
BackgroundIn a recent trial of intermittent preventive treatment in pregnancy (IPTp) in Uganda, dihydroartemisinin-piperaquine (DP) was superior to sulfadoxine-pyrimethamine (SP) in preventing maternal and placental malaria.MethodsWe compared genotypes using sequencing, fluorescent microsphere, and quantitative polymerase chain reaction assays at loci associated with drug resistance in Plasmodium falciparum isolated from subjects receiving DP or SP.ResultsConsidering aminoquinoline resistance, DP was associated with increased prevalences of mutations at pfmdr1 N86Y, pfmdr1 Y184F, and pfcrt K76T compared to SP (64.6% vs 27.4%, P < .001; 93.9% vs 59.2%, P < .001; and 87.7% vs 75.4%, P = .03, respectively). Increasing plasma piperaquine concentration at the time of parasitemia was associated with increasing pfmdr1 86Y prevalence; no infections with the N86 genotype occurred with piperaquine >2.75 ng/mL. pfkelch13 propeller domain polymorphisms previously associated with artemisinin resistance were not identified. Recently identified markers of piperaquine resistance were uncommon and not associated with DP. Considering antifolate resistance, SP was associated with increased prevalence of a 5-mutation haplotype (pfdhfr 51I, 59R, and 108N; pfdhps 437G and 581G) compared to DP (90.8% vs 60.0%, P = .001).ConclusionsIPTp selected for genotypes associated with decreased sensitivity to treatment regimens, but genotypes associated with clinically relevant DP resistance in Asia have not emerged in Uganda.
- Published
- 2017
32. The Diversity of the Plasmodium falciparum K13 Propeller Domain Did Not Increase after Implementation of Artemisinin-Based Combination Therapy in Uganda
- Author
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Sam L. Nsobya, Melissa D. Conrad, and Philip J. Rosenthal
- Subjects
Nonsynonymous substitution ,Protozoan Proteins ,artemisinin resistance ,0302 clinical medicine ,2.2 Factors relating to the physical environment ,Pharmacology (medical) ,Uganda ,Artemisinin ,Aetiology ,Genetics ,K13 ,0303 health sciences ,biology ,Single Nucleotide ,Pharmacology and Pharmaceutical Sciences ,Artemisinins ,Infectious Diseases ,Medical Microbiology ,Infection ,Sequence Analysis ,medicine.drug ,Falciparum ,Combination therapy ,030231 tropical medicine ,Plasmodium falciparum ,Single-nucleotide polymorphism ,Locus (genetics) ,Microbiology ,03 medical and health sciences ,Antimalarials ,Rare Diseases ,parasitic diseases ,medicine ,Humans ,Polymorphism ,Codon ,Pharmacology ,Genetic diversity ,030306 microbiology ,DNA ,biology.organism_classification ,medicine.disease ,Malaria ,Vector-Borne Diseases ,Good Health and Well Being ,Haplotypes ,Mutation ,Antimicrobial Resistance - Abstract
Artemisinin-based combination therapies (ACTs) are the standard of care to treat uncomplicated falciparum malaria. However, resistance to artemisinins, defined as delayed parasite clearance after therapy, has emerged in Southeast Asia, and the spread of resistance to sub-Saharan Africa could have devastating consequences. Artemisinin resistance has been associated in Southeast Asia with multiple nonsynonymous single nucleotide polymorphisms (NS-SNPs) in the propeller domain of the gene encoding the Plasmodium falciparum K13 protein (K13PD). Some K13PD NS-SNPs have been seen in Africa, but the relevance of these mutations is unclear. To assess whether ACT use has selected for specific K13PD mutations, we compared the K13PD genetic diversity in clinical isolates collected before and after the implementation of ACT use from seven sites across Uganda. We detected K13PD NS-SNPs in 16 of 683 (2.3%) clinical isolates collected between 1999 and 2004 and in 26 of 716 (3.6%) isolates collected between 2012 and 2016 (P = 0.16), representing a total of 29 different polymorphisms at 27 codons. Individual NS-SNPs were usually detected only once, and none were found in more than 0.7% of the isolates. Three SNPs (C469F, P574L, and A675V) associated with delayed clearance in Southeast Asia were seen in samples collected between 2012 and 2016, each in a single isolate. No differences in diversity following implementation of ACT use were found at any of the seven sites, nor was there evidence of selective pressures acting on the locus. Our results suggest that selection by ACTs is not impacting on K13PD diversity in Uganda.
- Published
- 2019
33. The Diversity of the
- Author
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Melissa D, Conrad, Sam L, Nsobya, and Philip J, Rosenthal
- Subjects
Plasmodium falciparum ,Protozoan Proteins ,Sequence Analysis, DNA ,Polymorphism, Single Nucleotide ,Artemisinins ,Epidemiology and Surveillance ,Antimalarials ,Haplotypes ,parasitic diseases ,Mutation ,Humans ,Uganda ,Malaria, Falciparum ,Codon - Abstract
Artemisinin-based combination therapies (ACTs) are the standard of care to treat uncomplicated falciparum malaria. However, resistance to artemisinins, defined as delayed parasite clearance after therapy, has emerged in Southeast Asia, and the spread of resistance to sub-Saharan Africa could have devastating consequences. Artemisinin resistance has been associated in Southeast Asia with multiple nonsynonymous single nucleotide polymorphisms (NS-SNPs) in the propeller domain of the gene encoding the Plasmodium falciparum K13 protein (K13PD). Some K13PD NS-SNPs have been seen in Africa, but the relevance of these mutations is unclear. To assess whether ACT use has selected for specific K13PD mutations, we compared the K13PD genetic diversity in clinical isolates collected before and after the implementation of ACT use from seven sites across Uganda. We detected K13PD NS-SNPs in 16 of 683 (2.3%) clinical isolates collected between 1999 and 2004 and in 26 of 716 (3.6%) isolates collected between 2012 and 2016 (P = 0.16), representing a total of 29 different polymorphisms at 27 codons. Individual NS-SNPs were usually detected only once, and none were found in more than 0.7% of the isolates. Three SNPs (C469F, P574L, and A675V) associated with delayed clearance in Southeast Asia were seen in samples collected between 2012 and 2016, each in a single isolate. No differences in diversity following implementation of ACT use were found at any of the seven sites, nor was there evidence of selective pressures acting on the locus. Our results suggest that selection by ACTs is not impacting on K13PD diversity in Uganda.
- Published
- 2019
34. The Impact of Antimalarial Resistance on the Genetic Structure ofPlasmodium falciparumin the DRC
- Author
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Nicholas J. Hathaway, Patrick W Marsh, Nicholas F Brazeau, Patrick K Tumwebaze, Jonathan B. Parr, Melchior Kashamuka Mwandagalirwa, Azra C. Ghani, Travis Fulton, James L. Myers-Hansen, Jonathan J. Juliano, Steven R Meshnick, Julie Gutman, William J. Moss, Robert Verity, Jeffrey A. Bailey, Modest Mulenga, Deus S. Ishengoma, Jeremiah Ngondi, Melissa D. Conrad, Douglas E. Norris, Anita Ghansah, Andrew P. Morgan, Philip J. Rosenthal, Ozkan Aydemir, Benedicta A. Mensah, Kyaw L. Thwai, Oliver J Watson, Antoinette K. Tshefu, Madeline Denton, and National Institutes of Health
- Subjects
0301 basic medicine ,Drug Resistance ,General Physics and Astronomy ,Drug resistance ,Gene flow ,Microbial ecology ,0302 clinical medicine ,Malaria, Falciparum ,lcsh:Science ,Genetics ,Principal Component Analysis ,0303 health sciences ,education.field_of_study ,Multidisciplinary ,Geography ,Chloroquine ,3. Good health ,Drug Combinations ,Pyrimethamine ,Genetic structure ,Democratic Republic of the Congo ,medicine.drug ,Genotype ,Science ,Plasmodium falciparum ,030231 tropical medicine ,Population ,Biology ,Polymorphism, Single Nucleotide ,Article ,General Biochemistry, Genetics and Molecular Biology ,Antimalarials ,03 medical and health sciences ,Sulfadoxine ,parasitic diseases ,medicine ,Humans ,Genetic variation ,education ,Genotyping ,030304 developmental biology ,Isolation by distance ,General Chemistry ,medicine.disease ,biology.organism_classification ,Sulfadoxine/pyrimethamine ,Malaria ,030104 developmental biology ,Haplotypes ,Mutation ,lcsh:Q ,Genome, Protozoan - Abstract
The Democratic Republic of the Congo (DRC) harbors 11% of global malaria cases, yet little is known about the spatial and genetic structure of the parasite population in that country. We sequence 2537 Plasmodium falciparum infections, including a nationally representative population sample from DRC and samples from surrounding countries, using molecular inversion probes - a high-throughput genotyping tool. We identify an east-west divide in haplotypes known to confer resistance to chloroquine and sulfadoxine-pyrimethamine. Furthermore, we identify highly related parasites over large geographic distances, indicative of gene flow and migration. Our results are consistent with a background of isolation by distance combined with the effects of selection for antimalarial drug resistance. This study provides a high-resolution view of parasite genetic structure across a large country in Africa and provides a baseline to study how implementation programs may impact parasite populations., The genome of the malaria parasite Plasmodium falciparum contains a record of past evolutionary forces. Here, using 2537 parasite sequences from the Democratic Republic of the Congo, the authors demonstrate how drug pressure and human movement have shaped the present-day parasite population.
- Published
- 2019
35. Changing Molecular Markers of Antimalarial Drug Sensitivity across Uganda
- Author
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Victor Asua, Melissa D. Conrad, Samuel L. Nsobya, Jennifer Legac, Philip J. Rosenthal, Grant Dorsey, Moses R. Kamya, Joanna Vinden, and Simon P. Kigozi
- Subjects
Protozoan Proteins ,Drug Resistance ,Drug resistance ,chemistry.chemical_compound ,0302 clinical medicine ,Chloroquine ,Aspartic Acid Endopeptidases ,Uganda ,Pharmacology (medical) ,Malaria, Falciparum ,Child ,media_common ,0303 health sciences ,biology ,Single Nucleotide ,Pharmacology and Pharmaceutical Sciences ,Artemisinins ,Infectious Diseases ,5.1 Pharmaceuticals ,Medical Microbiology ,Antifolate ,Quinolines ,HIV/AIDS ,Artemether ,Multidrug Resistance-Associated Proteins ,Development of treatments and therapeutic interventions ,Infection ,medicine.drug ,Falciparum ,Drug ,molecular markers ,media_common.quotation_subject ,Plasmodium falciparum ,030231 tropical medicine ,Lumefantrine Drug Combination ,Lumefantrine ,Polymorphism, Single Nucleotide ,Microbiology ,Antimalarials ,03 medical and health sciences ,Rare Diseases ,Piperaquine ,parasitic diseases ,Genetics ,medicine ,Humans ,Polymorphism ,Pharmacology ,antimalarial drug sensitivity ,030306 microbiology ,Artemether, Lumefantrine Drug Combination ,Wild type ,Membrane Transport Proteins ,biology.organism_classification ,Virology ,Malaria ,Vector-Borne Diseases ,Orphan Drug ,Good Health and Well Being ,chemistry ,Folic Acid Antagonists ,Antimicrobial Resistance - Abstract
The potential spread of antimalarial drug resistance to Africa, in particular for artemisinins and key partner drugs, is a major concern. We surveyed Plasmodium falciparum genetic markers associated with drug sensitivity on 3 occasions at ∼6-month intervals in 2016 and 2017 at 10 sites representing a range of epidemiological settings in Uganda. For putative drug transporters, we found continued evolution toward wild-type sequences associated with increased sensitivity to chloroquine. For pfcrt K76T, by 2017 the prevalence of the wild type was >60% at all sites and >90% at 6 sites. For the pfmdr1 N86Y and D1246Y alleles, wild type prevalence ranged from 80 to 100%. We found low prevalence of K13 propeller domain mutations, which are associated with artemisinin resistance in Asia, but one mutation previously identified in northern Uganda, 675V, was seen in 2.0% of samples, including 5.5% of those from the 3 northernmost sites. Amplification of the pfmdr1 and plasmepsin2 genes, associated elsewhere with decreased sensitivity to lumefantrine and piperaquine, respectively, was seen in
- Published
- 2019
36. Modeling Prevention of Malaria and Selection of Drug Resistance with Different Dosing Schedules of Dihydroartemisinin-Piperaquine Preventive Therapy during Pregnancy in Uganda
- Author
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Philip J. Rosenthal, Abel Kakuru, Jennifer Legac, Rada M. Savic, Prasanna Jagannathan, Grant Dorsey, Mary K. Muhindo, Patrick K Tumwebaze, Melissa D. Conrad, Moses R. Kamya, Diane V. Havlir, Erika Wallender, Daniel Mota, Richard Kajubi, Francesca T. Aweeka, and Nan Zhang
- Subjects
and promotion of well-being ,Drug Resistance ,Drug resistance ,Parasitemia ,antimalarial resistance ,0302 clinical medicine ,Dihydroartemisinin/piperaquine ,Pregnancy ,Medicine ,Pharmacology (medical) ,Uganda ,030212 general & internal medicine ,intermittent preventive treatment during pregnancy ,0303 health sciences ,biology ,dihydroartemisinin-piperaquine ,Pharmacology and Pharmaceutical Sciences ,Artemisinins ,Infectious Diseases ,Medical Microbiology ,Parasitic ,Combination ,Quinolines ,Drug Therapy, Combination ,Female ,PK/PD modeling ,Infection ,medicine.medical_specialty ,Clinical Therapeutics ,Microbiology ,03 medical and health sciences ,Antimalarials ,Young Adult ,Rare Diseases ,Drug Therapy ,Internal medicine ,Piperaquine ,parasitic diseases ,Humans ,Dosing ,3.3 Nutrition and chemoprevention ,Pharmacology ,030306 microbiology ,business.industry ,Prevention ,Plasmodium falciparum ,biology.organism_classification ,medicine.disease ,Prevention of disease and conditions ,Malaria ,Pregnancy Complications ,Vector-Borne Diseases ,Emerging Infectious Diseases ,Good Health and Well Being ,Pharmacodynamics ,Pregnancy Complications, Parasitic ,business - Abstract
Dihydroartemisinin-piperaquine (DHA-PQ) is under study for intermittent preventive treatment during pregnancy (IPTp), but it may accelerate selection for drug resistance. Understanding the relationships between piperaquine concentration, prevention of parasitemia, and selection for decreased drug sensitivity can inform control policies and optimization of DHA-PQ dosing. Piperaquine concentrations, measures of parasitemia, and Plasmodium falciparum genotypes associated with decreased aminoquinoline sensitivity in Africa (pfmdr1 86Y, pfcrt 76T) were obtained from pregnant Ugandan women randomized to IPTp with sulfadoxine-pyrimethamine (SP) or DHA-PQ. Joint pharmacokinetic/pharmacodynamic models described relationships between piperaquine concentration and the probability of genotypes of interest using nonlinear mixed effects modeling. An increase in the piperaquine plasma concentration was associated with a log-linear decrease in risk of parasitemia. Our models predicted that higher median piperaquine concentrations would be required to provide 99% protection against mutant infections than against wild-type infections (pfmdr1: N86, 9.6 ng/ml; 86Y, 19.6 ng/ml; pfcrt: K76, 6.5 ng/ml; 76T, 19.6 ng/ml). Comparing monthly, weekly, and daily dosing, daily low-dose DHA-PQ was predicted to result in the fewest infections and the fewest mutant infections per 1,000 pregnancies (predicted mutant infections for pfmdr1 86Y: SP monthly, 607; DHA-PQ monthly, 198; DHA-PQ daily, 1; for pfcrt 76T: SP monthly, 1,564; DHA-PQ monthly, 283; DHA-PQ daily, 1). Our models predict that higher piperaquine concentrations are needed to prevent infections with the pfmdr1/pfcrt mutant compared to those with wild-type parasites and that, despite selection for mutants by DHA-PQ, the overall burden of mutant infections is lower for IPTp with DHA-PQ than for IPTp with SP. (This study has been registered at ClinicalTrials.gov under identifier {"type":"clinical-trial","attrs":{"text":"NCT02282293","term_id":"NCT02282293"}}NCT02282293.)
- Published
- 2019
37. Artesunate/Amodiaquine Versus Artemether/Lumefantrine for the Treatment of Uncomplicated Malaria in Uganda: A Randomized Trial
- Author
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Kassahun Belay, Myers Lugemwa, Adoke Yeka, Melissa D. Conrad, Ruth Kigozi, Peter Okui, Grant Dorsey, Bryan K. Kapella, Philip J. Rosenthal, Moses R. Kamya, Michelle A. Chang, Charles Katureebe, and Sarah G. Staedke
- Subjects
Male ,0301 basic medicine ,medicine.medical_specialty ,Artemether/lumefantrine ,030106 microbiology ,030231 tropical medicine ,Parasitemia ,Amodiaquine ,Lumefantrine ,Major Articles and Brief Reports ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Internal medicine ,parasitic diseases ,medicine ,Humans ,Immunology and Allergy ,Uganda ,Artemether ,Malaria, Falciparum ,Fluorenes ,business.industry ,Artemether, Lumefantrine Drug Combination ,Artesunate/amodiaquine ,Infant ,medicine.disease ,Artemisinins ,Surgery ,Drug Combinations ,Regimen ,Infectious Diseases ,chemistry ,Ethanolamines ,Artesunate ,Child, Preschool ,Female ,business ,medicine.drug - Abstract
BACKGROUND In treating malaria in Uganda, artemether-lumefantrine (AL) has been associated with a lower risk of recurrent parasitemia, compared with artesunate-amodiaquine (AS/AQ), but changing treatment practices may have altered parasite susceptibility. METHODS We enrolled 602 children aged 6-59 months with uncomplicated falciparum malaria from 3 health centers in 2013-2014 and randomly assigned them to receive treatment with AS/AQ or AL. Primary outcomes were risks of recurrent parasitemia within 28 days, with or without adjustment to distinguish recrudescence from new infection. Drug safety and tolerability and Plasmodium falciparum resistance-mediating polymorphisms were assessed. RESULTS Of enrolled patients, 594 (98.7%) completed the 28-day study. Risks of recurrent parasitemia were lower with AS/AQ at all 3 sites (overall, 28.6% vs 44.6%; P < .001). Recrudescences were uncommon, and all occurred after AL treatment (0% vs 2.5%; P = .006). Recovery of the hemoglobin level was greater with AS/AQ (1.73 vs 1.39 g/dL; P = .04). Both regimens were well tolerated; serious adverse events were uncommon (1.7% in the AS/AQ group and 1.0% in the AL group). AS/AQ selected for mutant pfcrt/pfmdr1 polymorphisms and AL for wild-type pfcrt/pfmdr1 polymorphisms associated with altered drug susceptibility. CONCLUSIONS AS/AQ treatment was followed by fewer recurrences than AL treatment, contrasting with older data. Each regimen selected for polymorphisms associated with decreased treatment response. Research should consider multiple or rotating regimens to maintain treatment efficacies.
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- 2015
38. Changing Antimalarial Drug Sensitivities in Uganda
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Frida G. Ceja, Thomas Katairo, Oswald Byaruhanga, Melissa D. Conrad, Roland A. Cooper, Philip J. Rosenthal, Stephanie A Rasmussen, Samuel L. Nsobya, and Patrick K Tumwebaze
- Subjects
Male ,0301 basic medicine ,Artemether/lumefantrine ,medicine.medical_treatment ,Drug Resistance ,Protozoan Proteins ,Gene Expression ,Pharmacology ,chemistry.chemical_compound ,Parasitic Sensitivity Tests ,Dihydroartemisinin/piperaquine ,Chloroquine ,Aspartic Acid Endopeptidases ,Uganda ,Pharmacology (medical) ,Malaria, Falciparum ,Child ,Mefloquine ,Artemisinins ,Infectious Diseases ,Ethanolamines ,Child, Preschool ,Quinolines ,Female ,Multidrug Resistance-Associated Proteins ,medicine.drug ,Adolescent ,Plasmodium falciparum ,030106 microbiology ,Dihydroartemisinin ,Amodiaquine ,Lumefantrine ,Antimalarials ,Inhibitory Concentration 50 ,Young Adult ,03 medical and health sciences ,Mechanisms of Resistance ,Piperaquine ,parasitic diseases ,medicine ,Humans ,Fluorenes ,business.industry ,Infant ,Membrane Transport Proteins ,chemistry ,Mutation ,business - Abstract
Dihydroartemisinin-piperaquine (DP) has demonstrated excellent efficacy for the treatment and prevention of malaria in Uganda. However, resistance to both components of this regimen has emerged in Southeast Asia. The efficacy of artemether-lumefantrine, the first-line regimen to treat malaria in Uganda, has also been excellent, but continued pressure may select for parasites with decreased sensitivity to lumefantrine. To gain insight into current drug sensitivity patterns, ex vivo sensitivities were assessed and genotypes previously associated with altered drug sensitivity were characterized for 58 isolates collected in Tororo, Uganda, from subjects presenting in 2016 with malaria from the community or as part of a clinical trial comparing DP chemoprevention regimens. Compared to community isolates, those from trial subjects had lower sensitivities to the aminoquinolines chloroquine, monodesethyl amodiaquine, and piperaquine and greater sensitivities to lumefantrine and mefloquine, an observation consistent with DP selection pressure. Compared to results for isolates from 2010 to 2013, the sensitivities of 2016 community isolates to chloroquine, amodiaquine, and piperaquine improved (geometric mean 50% inhibitory concentrations [IC 50 ] = 248, 76.9, and 19.1 nM in 2010 to 2013 and 33.4, 14.9, and 7.5 nM in 2016, respectively [ P < 0.001 for all comparisons]), the sensitivity to lumefantrine decreased (IC 50 = 3.0 nM in 2010 to 2013 and 5.4 nM in 2016 [ P < 0.001]), and the sensitivity to dihydroartemisinin was unchanged (IC 50 = 1.4 nM). These changes were accompanied by decreased prevalence of transporter mutations associated with aminoquinoline resistance and low prevalence of polymorphisms recently associated with resistance to artemisinins or piperaquine. Antimalarial drug sensitivities are changing in Uganda, but novel genotypes associated with DP treatment failure in Asia are not prevalent.
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- 2017
39. Comparative Prevalence of
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Melissa D, Conrad, Daniel, Mota, Alex, Musiime, Maxwell, Kilama, John, Rek, Moses, Kamya, Grant, Dorsey, and Philip J, Rosenthal
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Male ,Polymorphism, Genetic ,Genotyping Techniques ,Plasmodium falciparum ,Drug Resistance ,Protozoan Proteins ,Infant ,Membrane Transport Proteins ,Articles ,DNA, Protozoan ,Child, Preschool ,parasitic diseases ,Anopheles ,Prevalence ,Animals ,Humans ,Female ,Uganda ,Malaria, Falciparum ,Multidrug Resistance-Associated Proteins ,Child ,Alleles - Abstract
Controlling malaria in high transmission areas, such as much of sub-Saharan Africa, will require concerted efforts to slow the spread of drug resistance and to impede malaria transmission. Understanding the fitness costs associated with the development of drug resistance, particularly within the context of transmission, can help guide policy decisions to accomplish these goals, as fitness constraints might lead to decreased transmission of drug-resistant strains. To determine if Plasmodium falciparum resistance–mediating polymorphisms impact on development at different parasite stages, we compared the genotypes of parasites infecting humans and mosquitoes from households in Uganda. Genotypes at 14 polymorphic loci in genes encoding putative transporters (pfcrt and pfmdr1) and folate pathway enzymes (pfdhfr and pfdhps) were characterized using ligase detection reaction-fluorescent microsphere assays. In paired analysis using the Wilcoxon signed-rank test, prevalences of mutations at 12 loci did not differ significantly between parasites infecting humans and mosquitoes. However, compared with parasites infecting humans, those infecting mosquitoes were enriched for the pfmdr1 86Y mutant allele (P = 0.0001) and those infecting Anopheles gambiae s.s. were enriched for the pfmdr1 86Y (P = 0.0001) and pfcrt 76T (P = 0.0412) mutant alleles. Our results suggest modest directional selection resulting from varied fitness costs during the P. falciparum life cycle. Better appreciation of the fitness implications of drug resistance mediating mutations can inform optimal malaria treatment and prevention strategies.
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- 2017
40. Comparative Impacts Over 5 Years of Artemisinin-Based Combination Therapies on Plasmodium falciparum Polymorphisms That Modulate Drug Sensitivity in Ugandan Children
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Jordan W. Tappero, Emmanuel Arinaitwe, Melissa D. Conrad, Norbert P. LeClair, Abel Kakuru, Philip J. Rosenthal, Humphrey Wanzira, Victor Bigira, Mary K. Muhindo, Moses R. Kamya, Bryan Greenhouse, and Grant Dorsey
- Subjects
Male ,Artemether/lumefantrine ,Drug Resistance ,Pharmacology ,artemether-lumefantrine ,Medical and Health Sciences ,chemistry.chemical_compound ,pfmdr1 ,Dihydroartemisinin/piperaquine ,Immunology and Allergy ,Uganda ,Artemether ,Malaria, Falciparum ,Artemisinin ,Child ,dihydroartemisinin-piperaquine ,Biological Sciences ,Artemisinins ,Infectious Diseases ,Child, Preschool ,HIV/AIDS ,Female ,Infection ,medicine.drug ,Falciparum ,Plasmodium falciparum ,Clinical Trials and Supportive Activities ,Amodiaquine ,Biology ,Lumefantrine ,Microbiology ,pfcrt ,Major Articles and Brief Reports ,Rare Diseases ,Genetic ,Clinical Research ,Piperaquine ,parasitic diseases ,Genetics ,medicine ,Humans ,Polymorphism ,Preschool ,Alleles ,Polymorphism, Genetic ,Infant ,medicine.disease ,Malaria ,Vector-Borne Diseases ,Orphan Drug ,Good Health and Well Being ,chemistry ,Immunology - Abstract
(See the editorial commentary by Taylor and Juliano on pages 335–7.) Artemisinin-based combination therapies (ACTs) have shown excellent efficacy and are now recommended to treat falciparum malaria in nearly all countries [1]. ACTs include potent, short-acting artemisinins that rapidly reduce parasite biomass and alleviate malaria symptoms and longer-acting partner drugs that improve antimalarial efficacy and reduce the risk of selection for artemisinin resistance [2]. However, as partner drugs circulate well after artemisinins have been cleared, there is concern that subsequent infections will be exposed to subtherapeutic concentrations, facilitating the selection of parasites with reduced sensitivity to the partner drugs. Artemether-lumefantrine (AL) is the most widely recommended ACT in Africa and the national malaria treatment regimen in Uganda [1, 3]. It has shown outstanding efficacy [4, 5], but treatment selects in recurrent Plasmodium falciparum infections for polymorphisms in pfcrt and pfmdr1 [6–11]—genes encoding 2 putative drug transporters—that reduce sensitivity to artemether, lumefantrine, and other antimalarial drugs [12–15]. AL exerts an opposite selective pressure compared to that of the aminoquinolines chloroquine and amodiaquine. Specifically, the aminoquinolines select for the mutant pfcrt 76T, pfmdr1 86Y, and pfmdr1 1246Y alleles, which decrease sensitivity to these drugs, whereas AL selects for the wild-type alleles [6–11, 16]. AL also selected for the I876 polymorphism in pfmrp1, which encodes another putative drug transporter, in Tanzania [17]. Three additional pfmdr1 polymorphisms (S1034C, N1042D, and increased gene copy number) are associated with altered sensitivity to some drugs, but are primarily seen outside of Africa [12, 15, 18–20]. Ex vivo sensitivities of field isolates to lumefantrine have varied widely, but clinically relevant resistance does not appear to be a problem [14, 21, 22]. Analysis of parasites selected in vitro for high-level lumefantrine resistance demonstrated multiple differentially expressed genes, including pfmdr1, but the phenotype was unstable [23]. Dihydroartemisinin-piperaquine (DP) has shown excellent efficacy in clinical trials in Africa [16, 24–27], but has only been adopted as a first-line therapy in Southeast Asia [1]. Particularly in areas with high malaria transmission intensity, DP benefits from the pharmacokinetics of piperaquine, which has a much longer half-life (3–4 weeks) than that of lumefantrine (3–5 days) and other ACT partner drugs [28], yielding a long posttreatment prophylactic effect [5, 24, 27]. Piperaquine was used extensively to prevent and treat malaria decades ago in China [29, 30], but reported resistance led to reduced use by the 1980s. More recently, with implementation of DP as a standard therapy, piperaquine resistance does not appear to be a major problem, although ex vivo sensitivities of field isolates to piperaquine have varied [14, 22, 31, 32]. Mechanisms of resistance to piperaquine are poorly understood. Parasites selected in vitro for resistance acquired a number of genetic changes, including a novel mutation in pfcrt and deamplification of pfmdr1, but the phenotype was unstable [33]. AL replaced chloroquine plus sulfadoxine-pyrimethamine as the first-line regimen for uncomplicated malaria in Uganda in 2004, although implementation did not begin until 2006 and was initially slow [34, 35]. With improved utilization of AL in recent years, it was of interest to determine the prevalence over time of parasite polymorphisms that alter sensitivity to ACT components and to determine how use of AL impacts upon these polymorphisms. Therefore, we analyzed the prevalence of polymorphisms of interest in samples from a 5-year longitudinal trial comparing the antimalarial efficacies of AL and DP in Ugandan children. Polymorphisms associated with reduced sensitivity to AL increased markedly in prevalence over the course of the study, and this increase was greater in children treated with AL compared to those treated with DP, consistent with our demonstration of opposite selective pressures of the 2 regimens.
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- 2014
41. Optimization of a Ligase Detection Reaction-Fluorescent Microsphere Assay for Characterization of Resistance-Mediating Polymorphisms in African Samples of Plasmodium falciparum
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Samuel L. Nsobya, Melissa D. Conrad, Philip J. Rosenthal, Frederick N. Baliraine, Christian Nsanzabana, and Norbert P. LeClair
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Falciparum ,Microbiology (medical) ,Plasmodium falciparum ,Drug Resistance ,Drug resistance ,Medical and Health Sciences ,Microbiology ,Ligases ,Antimalarials ,Rare Diseases ,Parasitic Sensitivity Tests ,Genetic ,Clinical Research ,parasitic diseases ,Genotype ,Genetics ,Humans ,Uganda ,Multiplex ,Genetic Testing ,Malaria, Falciparum ,Polymorphism ,Allele ,Gene ,Polymorphism, Genetic ,Agricultural and Veterinary Sciences ,biology ,Biological Sciences ,Amplicon ,biology.organism_classification ,Molecular biology ,Microspheres ,Malaria ,High-Throughput Screening Assays ,Vector-Borne Diseases ,Blood ,Infectious Diseases ,Good Health and Well Being ,Molecular Diagnostic Techniques ,Parasitology ,Restriction fragment length polymorphism ,Infection - Abstract
Genetic polymorphisms in the malaria parasite Plasmodium falciparum mediate alterations in sensitivity to important antimalarial drugs. Surveillance for these polymorphisms is helpful in assessing the prevalence of drug resistance and designing strategies for malaria control. Multiple methods are available for the assessment of P. falciparum genetic polymorphisms, but they suffer from low throughput, technical limitations, and high cost. We have optimized and tested a multiplex ligase detection reaction-fluorescent microsphere (LDR-FM) assay for the identification of important P. falciparum genetic polymorphisms. For 84 clinical samples from Kampala, Uganda, a region where both transmission intensity and infection complexity are high, DNA was extracted from dried blood spots, genes of interest were amplified, amplicons were subjected to multiplex ligase detection reactions to add bead-specific oligonucleotides and biotin, fragments were hybridized to magnetic beads, and polymorphism prevalences were assessed fluorometrically in a multiplex format. A total of 19 alleles from the pfcrt , pfmdr1 , pfmrp1 , pfdhfr , and pfdhps genes were analyzed by LDR-FM and restriction fragment length polymorphism (RFLP) analyses. Considering samples with results from the two assays, concordance between the assays was good, with 78 to 100% of results identical at individual alleles, most nonconcordant results differing only between a mixed and pure genotype call, and full disagreement at individual alleles in only 0 to 3% of results. We estimate that the LDR-FM assay offers much higher throughput and lower cost than RFLP. Our results suggest that the LDR-FM system offers an accurate high-throughput means of classifying genetic polymorphisms in field samples of P. falciparum .
- Published
- 2013
42. Genetic diversity ofTrichomonas vaginalisreinfection in HIV-positive women
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Patricia Kissinger, Norine Schmidt, David H. Martin, Melissa D. Conrad, and Jane M. Carlton
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Adult ,Genotype ,Population ,Trichomonas ,Trichomonas Infections ,HIV Infections ,Dermatology ,Biology ,medicine.disease_cause ,Article ,Acquired immunodeficiency syndrome (AIDS) ,Recurrence ,Genetic variation ,Trichomonas vaginalis ,medicine ,Humans ,education ,Genotyping ,Genetics ,Molecular Epidemiology ,Genetic diversity ,education.field_of_study ,Molecular epidemiology ,Genetic Variation ,medicine.disease ,biology.organism_classification ,DNA Fingerprinting ,Virology ,Infectious Diseases ,Female ,Microsatellite Repeats - Abstract
Objectives Recently developed genotyping tools allow better understanding of Trichomonas vaginalis population genetics and epidemiology. These tools have yet to be applied to T vaginalis collected from HIV + populations, where understanding the interaction between the pathogens is of great importance due to the correlation between T vaginalis infection and HIV transmission. The objectives of the study were twofold: first, to compare the genetic diversity and population structure of T vaginalis collected from HIV + women with parasites from reference populations; second, to use the genetic markers to perform a case study demonstrating the usefulness of these techniques in investigating the mechanisms of repeat infections. Methods Repository T vaginalis samples from a previously described treatment trial were genotyped at 11 microsatellite loci. Estimates of genetic diversity and population structure were determined using standard techniques and compared with previously reported estimates of global populations. Genotyping data were used in conjunction with behavioural data to evaluate mechanisms of repeat infections. Results T vaginalis from HIV + women maintain many of the population genetic characteristics of parasites from global reference populations. Although there is evidence of reduced diversity and bias towards type 1 parasites in the HIV + population, the populations share a two-type population structure and parasite haplotypes. Genotyping/behavioural data suggest that 36% (12/33) of repeat infections in HIV + women can be attributed to treatment failure. Conclusions T vaginalis infecting HIV + women is not genetically distinct from T vaginalis infecting reference populations. Information from genotyping can be valuable for understanding mechanisms of repeat infections.
- Published
- 2013
43. Changing Antimalarial Drug Resistance Patterns Identified by Surveillance at Three Sites in Uganda
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Bryan Greenhouse, Grant Dorsey, Patrick K Tumwebaze, Sarah G. Staedke, Andrew Walakira, Joaniter I. Nankabirwa, Adoke Yeka, Samuel L. Nsobya, Melissa D. Conrad, Philip J. Rosenthal, Stephen Tukwasibwe, Victor Asua, Aimee R. Taylor, Emmanuel Ruhamyankaka, and Moses R. Kamya
- Subjects
0301 basic medicine ,Adolescent ,medicine.medical_treatment ,030106 microbiology ,Genes, Protozoan ,Plasmodium falciparum ,Drug Resistance ,Protozoan Proteins ,Dihydroartemisinin ,Drug resistance ,Biology ,Lumefantrine ,Polymorphism, Single Nucleotide ,03 medical and health sciences ,chemistry.chemical_compound ,Antimalarials ,Piperaquine ,parasitic diseases ,medicine ,Immunology and Allergy ,Humans ,Uganda ,Artemether ,Artemisinin ,Malaria, Falciparum ,Genetics ,Fluorenes ,Brief Report ,Membrane Transport Proteins ,Sequence Analysis, DNA ,DNA, Protozoan ,medicine.disease ,biology.organism_classification ,Artemisinins ,3. Good health ,Infectious Diseases ,Cross-Sectional Studies ,chemistry ,Ethanolamines ,Mutation ,Aminoquinolines ,Folic Acid Antagonists ,Female ,Multidrug Resistance-Associated Proteins ,Malaria ,medicine.drug - Abstract
We assessed Plasmodium falciparum drug resistance markers in parasites collected in 2012, 2013, and 2015 at 3 sites in Uganda. The prevalence and frequency of parasites with mutations in putative transporters previously associated with resistance to aminoquinolines, but increased sensitivity to lumefantrine (pfcrt 76T; pfmdr1 86Y and 1246Y), decreased markedly at all sites. Antifolate resistance mutations were common, with apparent emergence of mutations (pfdhfr 164L; pfdhps 581G) associated with high level resistance. K13 mutations linked to artemisinin resistance were uncommon and did not increase over time. Changing malaria treatment practices have been accompanied by profound changes in markers of resistance.
- Published
- 2016
44. Intermittent preventive treatment with dihydroartemisinin-piperaquine in Ugandan schoolchildren selects for Plasmodium falciparum transporter polymorphisms that modify drug sensitivity
- Author
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Melissa D. Conrad, Philip J. Rosenthal, Stephen Tukwasibwe, Sam L. Nsobya, Bonnie Wandera, Sarah G. Staedke, Simon Brooker, Joaniter I. Nankabirwa, Jennifer Legac, Grant Dorsey, Patrick K Tumwebaze, and Moses R. Kamya
- Subjects
Male ,0301 basic medicine ,medicine.medical_specialty ,Adolescent ,Plasmodium falciparum ,030106 microbiology ,Protozoan Proteins ,Drug resistance ,Parasitemia ,Asymptomatic ,Gastroenterology ,Epidemiology and Surveillance ,Antimalarials ,03 medical and health sciences ,0302 clinical medicine ,Dihydroartemisinin/piperaquine ,Internal medicine ,parasitic diseases ,Genotype ,medicine ,Humans ,Uganda ,Pharmacology (medical) ,030212 general & internal medicine ,Malaria, Falciparum ,Child ,Pharmacology ,Polymorphism, Genetic ,biology ,business.industry ,Incidence (epidemiology) ,Membrane Transport Proteins ,biology.organism_classification ,medicine.disease ,Artemisinins ,3. Good health ,Infectious Diseases ,Immunology ,Quinolines ,Female ,Pre-Exposure Prophylaxis ,Multidrug Resistance-Associated Proteins ,medicine.symptom ,business ,Malaria - Abstract
Dihydroartemisinin-piperaquine (DP) offers prolonged protection against malaria, but its impact on Plasmodium falciparum drug sensitivity is uncertain. In a trial of intermittent preventive treatment in schoolchildren in Tororo, Uganda, in 2011 to 2012, monthly DP for 1 year decreased the incidence of malaria by 96% compared to placebo; DP once per school term offered protection primarily during the first month after therapy. To assess the impact of DP on selection of drug resistance, we compared the prevalence of key polymorphisms in isolates that emerged at different intervals after treatment with DP. Blood obtained monthly and at each episode of fever was assessed for P. falciparum parasitemia by microscopy. Samples from 160 symptomatic and 650 asymptomatic episodes of parasitemia were assessed at 4 loci (N86Y, Y184F, and D1246Y in pfmdr1 and K76T in pfcrt ) that modulate sensitivity to aminoquinoline antimalarials, utilizing a ligase detection reaction-fluorescent microsphere assay. For pfmdr1 N86Y and pfcrt K76T, but not the other studied polymorphisms, the prevalences of mutant genotypes were significantly greater in children who had received DP within the past 30 days than in those not treated within 60 days (86Y, 18.0% versus 8.3% [ P = 0.03]; 76T, 96.0% versus 86.1% [ P = 0.05]), suggesting selective pressure of DP. Full sequencing of pfcrt in a subset of samples did not identify additional polymorphisms selected by DP. In summary, parasites that emerged soon after treatment with DP were more likely than parasites not under drug pressure to harbor pfmdr1 and pfcrt polymorphisms associated with decreased sensitivity to aminoquinoline antimalarials. (This study has been registered at ClinicalTrials.gov under no. NCT01231880.)
- Published
- 2016
45. The evolution of infectious agents in relation to sex in animals and humans: brief discussions of some individual organisms
- Author
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Welkin E. Johnson, William M. Shafer, Paul M. Sharp, Ian N. Clarke, Richard Eberle, Shaun Tyler, Peter Norberg, Steven A. Sullivan, Tomas Bergström, Alberto Severini, R. Palmer Beasley, Guido Silvestri, David L. Reed, Andrew J. Davison, Teresa Lagergård, Jonas Blomberg, Beatrice H. Hahn, Magnus Unemo, Shelley F. Walton, Russell W. Currier, Melissa D. Conrad, Jane M. Carlton, Timothy D. Read, and Sheila A. Lukehart
- Subjects
Cognitive science ,medicine.medical_specialty ,Sexual transmission ,General Neuroscience ,Public health ,Perspective (graphical) ,Zoology ,Biological evolution ,Biology ,General Biochemistry, Genetics and Molecular Biology ,History and Philosophy of Science ,Sexual behavior ,medicine ,Relation (history of concept) ,Biological sciences ,Infectious agent - Abstract
The following series of concise summaries addresses the evolution of infectious agents in relation to sex in animals and humans from the perspective of three specific questions: (1) what have we learned about the likely origin and phylogeny, up to the establishment of the infectious agent in the genital econiche, including the relative frequency of its sexual transmission; (2) what further research is needed to provide additional knowledge on some of these evolutionary aspects; and (3) what evolutionary considerations might aid in providing novel approaches to the more practical clinical and public health issues facing us currently and in the future?
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- 2011
46. Microsatellite polymorphism in the sexually transmitted human pathogen Trichomonas vaginalis indicates a genetically diverse parasite
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Steven A. Sullivan, Melissa D. Conrad, Jane M. Carlton, J.A. Upcroft, Jan Tachezy, Zuzana Zubáčová, and Linda A. Dunn
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Molecular Sequence Data ,Population ,Population genetics ,Biology ,medicine.disease_cause ,Genome ,Article ,Trichomonas vaginalis ,medicine ,Cluster Analysis ,Humans ,education ,Molecular Biology ,In Situ Hybridization, Fluorescence ,Phylogeny ,Genetics ,Genetic diversity ,education.field_of_study ,Polymorphism, Genetic ,Sequence Analysis, DNA ,DNA, Protozoan ,DNA Fingerprinting ,DNA profiling ,Genetic marker ,Microsatellite ,Parasitology ,Microsatellite Repeats - Abstract
Given the growing appreciation of serious health sequelae from widespread Trichomonas vaginalis infection, new tools are needed to study the parasite's genetic diversity. To this end we have identified and characterized a panel of 21 microsatellites and six single-copy genes from the T. vaginalis genome, using seven laboratory strains of diverse origin. We have (1) adapted our microsatellite typing method to incorporate affordable fluorescent labeling, (2) determined that the microsatellite loci remain stable in parasites continuously cultured for up to 17 months, and (3) evaluated microsatellite marker coverage of the six chromosomes that comprise the T. vaginalis genome, using fluorescent in situ hybridization (FISH). We have used the markers to show that T. vaginalis is a genetically diverse parasite in a population of commonly used laboratory strains. In addition, we have used phylogenetic methods to infer evolutionary relationships from our markers in order to validate their utility in future population analyses. Our panel is the first series of robust polymorphic genetic markers for T. vaginalis that can be used to classify and monitor lab strains, as well as provide a means to measure the genetic diversity and population structure of extant and future T. vaginalis isolates.
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- 2011
47. Synteny and candidate gene prediction using an anchored linkage map of Astyanax mexicanus
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Meredith E. Protas, Richard Borowsky, Melissa D. Conrad, P. Scheid, Oriol Vidal, Clifford J. Tabin, William R. Jeffery, and Joshua B. Gross
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Linkage (software) ,Genetics ,Candidate gene ,Multidisciplinary ,Genetic Linkage ,Tetraodontiformes ,Gene Networks in Development and Evolution Special Feature Sackler Colloquium ,Quantitative Trait Loci ,Danio ,Chromosome Mapping ,Ribs ,Biology ,Quantitative trait locus ,Eye ,biology.organism_classification ,Biological Evolution ,Synteny ,Genome ,Evolutionary biology ,Genetic linkage ,Animals ,Selection, Genetic ,Gene ,Zebrafish - Abstract
The blind Mexican cave tetra, Astyanax mexicanus , is a unique model system for the study of parallelism and the evolution of cave-adapted traits. Understanding the genetic basis for these traits has recently become feasible thanks to production of a genome-wide linkage map and quantitative trait association analyses. The selection of suitable candidate genes controlling quantitative traits remains challenging, however, in the absence of a physical genome. Here, we describe the integration of multiple linkage maps generated in four separate crosses between surface, cave, and hybrid forms of A. mexicanus . We performed exhaustive BLAST analyses of genomic markers populating this integrated map against sequenced genomes of numerous taxa, ranging from yeast to amniotes. We found the largest number of identified sequences (228), with the most expect (E) values −5 (95), in the zebrafish Danio rerio . The most significant hits were assembled into an “anchored” linkage map with Danio , revealing numerous regions of conserved synteny, many of which are shared across critical regions of identified quantitative trait loci (QTL). Using this anchored map, we predicted the positions of 21 test genes on the integrated linkage map and verified that 18 of these are found in locations homologous to their chromosomal positions in D. rerio . The anchored map allowed the identification of four candidate genes for QTL relating to rib number and eye size. The map we have generated will greatly accelerate the production of viable lists of additional candidate genes involved in the development and evolution of cave-specific traits in A. mexicanus .
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- 2008
48. Multi-trait evolution in a cave fish, Astyanax mexicanus
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Joshua B. Gross, Richard Borowsky, Clifford J. Tabin, Melissa D. Conrad, Meredith E. Protas, Oriol Vidal, and Inna Tabansky
- Subjects
Genetics ,geography ,geography.geographical_feature_category ,Cavefish ,Quantitative trait locus ,Biology ,Phenotype ,Genome ,Cave ,Family-based QTL mapping ,Allele ,Gene ,Ecology, Evolution, Behavior and Systematics ,Developmental Biology - Abstract
SUMMARY When surface species colonize caves, a characteristic suite of traits eventually evolves over time, regardless of species. The genetic basis of the inevitable appearance of these very similar phenotypes was investigated through quantitative trait loci (QTL) mapping of 12 traits that differ significantly between the recently evolved (
- Published
- 2008
49. Absence of Putative Artemisinin Resistance Mutations Among Plasmodium falciparum in Sub-Saharan Africa: A Molecular Epidemiologic Study
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Meghna Desai, Jonathan J. Juliano, Andreas Mårtensson, John M. Vulule, Steven R. Meshnick, Ann M. Moormann, Billy Ngasala, Harry Tagbor, Ogobara K. Doumbo, Sheick Oumar Coulibaly, John V. Williams, Simon Kariuki, Melissa D. Conrad, Fanta Njie, Steve M. Taylor, Kassoum Kayentao, Jeffrey A. Bailey, Philip J. Rosenthal, Christian M. Parobek, Don P. Mathanga, Julie Gutman, Kalifa Bojang, Derrick K. DeConti, Antoinette Tshefu, Brian Greenwood, Feiko O. ter Kuile, and Other departments
- Subjects
Male ,Drug resistance ,artemisinin resistance ,Pharmacology ,molecular epidemiology ,Medical and Health Sciences ,Gene Frequency ,Pregnancy ,Genotype ,Prevalence ,2.1 Biological and endogenous factors ,2.2 Factors relating to the physical environment ,Immunology and Allergy ,Aetiology ,Malaria, Falciparum ,Artemisinin ,Child ,Genetics ,Molecular Epidemiology ,High-Throughput Nucleotide Sequencing ,Biological Sciences ,Artemisinins ,Infectious Diseases ,Child, Preschool ,falciparum malaria ,Female ,Infection ,medicine.drug ,Falciparum ,Adult ,Plasmodium falciparum ,Biology ,Southeast asian ,Microbiology ,Vaccine Related ,Major Articles and Brief Reports ,Antimalarials ,Rare Diseases ,Genetic ,Biodefense ,parasitic diseases ,medicine ,Humans ,Polymorphism ,Preschool ,Allele frequency ,Africa South of the Sahara ,drug resistance ,Polymorphism, Genetic ,Molecular epidemiology ,Prevention ,biology.organism_classification ,Malaria ,Vector-Borne Diseases ,Good Health and Well Being ,Mutation ,Antimicrobial Resistance ,Selective sweep - Abstract
Plasmodium falciparum parasites that are resistant to artemisinins have been detected in Southeast Asia. Resistance is associated with several polymorphisms in the parasite's K13-propeller gene. The molecular epidemiology of these artemisinin resistance genotypes in African parasite populations is unknown. We developed an assay to quantify rare polymorphisms in parasite populations that uses a pooled deep-sequencing approach to score allele frequencies, validated it by evaluating mixtures of laboratory parasite strains, and then used it to screen P. falciparum parasites from >1100 African infections collected since 2002 from 14 sites across sub-Saharan Africa. We found no mutations in African parasite populations that are associated with artemisinin resistance in Southeast Asian parasites. However, we observed 15 coding mutations, including 12 novel mutations, and limited allele sharing between parasite populations, consistent with a large reservoir of naturally occurring K13-propeller variation. Although polymorphisms associated with artemisinin resistance in P. falciparum in Southeast Asia are not prevalent in sub-Saharan Africa, numerous K13-propeller coding polymorphisms circulate in Africa. Although their distributions do not support a widespread selective sweep for an artemisinin-resistant phenotype, the impact of these mutations on artemisinin susceptibility is unknown and will require further characterization. Rapid, scalable molecular surveillance offers a useful adjunct in tracking and containing artemisinin resistance.
- Published
- 2015
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50. Impact of antimalarial treatment and chemoprevention on the drug sensitivity of malaria parasites isolated from ugandan children
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Philip J. Rosenthal, Roland A. Cooper, Samuel L. Nsobya, Melissa D. Conrad, Jessica Bloome, Benjamin Kozak, Moses R. Kamya, Diane V. Havlir, Abel Kakuru, Oswald Byaruhanga, Victor Bigira, Jiri Gut, Jennifer Legac, Norbert P. LeClair, Bryan Greenhouse, James Kapisi, Jaffer Okiring, Grant Dorsey, Patrick K Tumwebaze, Andrew Walakira, and Christine Nakazibwe
- Subjects
medicine.medical_treatment ,Protozoan Proteins ,Pharmacology ,chemistry.chemical_compound ,Parasitic Sensitivity Tests ,Chloroquine ,Pharmacology (medical) ,Uganda ,Child ,Quinine ,Clinical Trials as Topic ,biology ,Pharmacology and Pharmaceutical Sciences ,Artemisinins ,Infectious Diseases ,Medical Microbiology ,Ethanolamines ,Child, Preschool ,Quinolines ,Multidrug Resistance-Associated Proteins ,Infection ,medicine.drug ,Plasmodium falciparum ,Dihydroartemisinin ,Amodiaquine ,Lumefantrine ,Microbiology ,Vaccine Related ,Antimalarials ,Rare Diseases ,Genetic ,Mechanisms of Resistance ,Piperaquine ,parasitic diseases ,medicine ,Humans ,Polymorphism ,Preschool ,Fluorenes ,Polymorphism, Genetic ,business.industry ,Prevention ,Infant ,Membrane Transport Proteins ,medicine.disease ,biology.organism_classification ,Malaria ,Vector-Borne Diseases ,Emerging Infectious Diseases ,Orphan Drug ,Good Health and Well Being ,chemistry ,business - Abstract
Changing treatment practices may be selecting for changes in the drug sensitivity of malaria parasites. We characterized ex vivo drug sensitivity and parasite polymorphisms associated with sensitivity in 459 Plasmodium falciparum samples obtained from subjects enrolled in two clinical trials in Tororo, Uganda, from 2010 to 2013. Sensitivities to chloroquine and monodesethylamodiaquine varied widely; sensitivities to quinine, dihydroartemisinin, lumefantrine, and piperaquine were generally good. Associations between ex vivo drug sensitivity and parasite polymorphisms included decreased chloroquine and monodesethylamodiaquine sensitivity and increased lumefantrine and piperaquine sensitivity with pfcrt 76T, as well as increased lumefantrine sensitivity with pfmdr1 86Y, Y184, and 1246Y. Over time, ex vivo sensitivity decreased for lumefantrine and piperaquine and increased for chloroquine, the prevalences of pfcrt K76 and pfmdr1 N86 and D1246 increased, and the prevalences of pfdhfr and pfdhps polymorphisms associated with antifolate resistance were unchanged. In recurrent infections, recent prior treatment with artemether-lumefantrine was associated with decreased ex vivo lumefantrine sensitivity and increased prevalence of pfcrt K76 and pfmdr1 N86, 184F, and D1246. In children assigned chemoprevention with monthly dihydroartemisinin-piperaquine with documented circulating piperaquine, breakthrough infections had increased the prevalence of pfmdr1 86Y and 1246Y compared to untreated controls. The noted impacts of therapy and chemoprevention on parasite polymorphisms remained significant in multivariate analysis correcting for calendar time. Overall, changes in parasite sensitivity were consistent with altered selective pressures due to changing treatment practices in Uganda. These changes may threaten the antimalarial treatment and preventive efficacies of artemether-lumefantrine and dihydroartemisinin-piperaquine, respectively.
- Published
- 2014
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