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Plasmodium falciparumerythrocyte membrane protein-1s (PfEMP1s), diverse malaria proteins expressed on the infected erythrocyte surface, play an important role in pathogenesis, mediating adhesion to host vascular endothelium. Antibodies to particular non-CD36-binding PfEMP1s are associated with protection against severe disease. We hypothesized that given lifelongP. falciparumexposure, Malian adults would have broad PfEMP1 serorecognition and high seroreactivity levels during follow-up, particularly to non-CD36-binding PfEMP1s such as those that attach to endothelial protein C receptor (EPCR) and intercellular adhesion molecule-1 (ICAM-1). Using a protein microarray, we determined serologic responses to 166 reference PfEMP1 fragments during a dry and subsequent malaria transmission season in Malian adults. Malian adult sera had PfEMP1 serologic responses throughout the year, with decreased reactivity to a small subset of PfEMP1 fragments during the dry season and increases in reactivity to a different subset of PfEMP1 fragments during the subsequent peak malaria transmission season, especially for intracellular PfEMP1 domains. For some individuals, PfEMP1 serologic responses increased after the dry season, suggesting antigenic switching during asymptomatic infection. Adults were more likely to experience variable serorecognition of CD36-binding PfEMP1s than non-CD36-binding PfEMP1s that bind EPCR or ICAM-1, which remained serorecognized throughout the year. Sustained seroreactivity to non-CD36-binding PfEMP1s throughout adulthood amid seasonal fluctuation patterns may reflect underlying protective severe malaria immunity and merits further investigation. more...

Many African countries have reported declines in malaria incidence, attributed to the implementation of control strategies. In Mali, artemisinin-based combination therapy (ACT) was introduced in 2004, and long-lasting insecticide-treated nets (LLINs) have been partially distributed free of charge since 2007. In the Malian town of Bandiagara, a study conducted from 2009 to 2013 showed a stable incidence of malaria compared with 1999, despite the implementation of ACTs and LLINs. Since 2016, seasonal malaria chemoprevention has been scaled up across the country. In addition to these strategies, the population of Bandiagara benefited from indoor residual spray implementation in 2017 and 2018 and continued universal bed net coverage. This study aimed to measure the incidence of malaria in Bandiagara, given this recent scaling up of control strategies. A cohort of 300 children aged 6 months to 15 years was followed up from October 2017 to December 2018. We performed monthly cross-sectional surveys to measure anemia and the prevalence of malaria infection by microscopy. The overall incidence of symptomatic malaria was 0.5 episodes/person-year. Malaria incidence in children up to 5 years old significantly declined since 2012 and since 1999 (incidence rate ratio estimates: 6.7 [95% CI: 4.2–11.4] and 13.5 [95% CI: 8.4–22.7]), respectively. The average prevalence of malaria parasitemia was 6.7%. Malaria incidence was higher in children older than 5 years than in those younger than 5 years, highlighting the need to extend malaria control efforts to these older children. more...

Summary: A malignant tumour that develops from the bronchial epithelium and then invades the lungs. It ranks third after colorectal and breast cancer. In Mali, computed tomography (CT) is the main imaging tool used at all stages of treatment. We had initiated this study with the objective of specifying the place of CT in the diagnosis of primary bronchopulmonary cancer at the hospital of Mali. Method: This is a prospective and descriptive study conducted by the Medical Imaging and Thoracic Surgery departments at Mali Hospital from March 2014 to February 2015. All the patients who have benefited from a CT scan and presenting at least one histologically confirmed bronchopulmonary tumor were included. Results: We were recruiting 60 patients with bronchopulmonary cancers out of 500 referred for a thoracic CT scan performed, a frequency of 12%. There was one male patient with a sex ratio of 4H/1F. The average age was 60 years. The history of smoking was 85%. The symptoms were dominated by general condition (63.33%), cough (25%) and haemoptysis (58.33%). CT scans were performed in all patients. The lesions were located more in the lower lobes (71%). The tumours were: heterogeneous tissue density (70%), spiculated contours (80%), and the histology was more non-small cell carcinoma. Conclusion: The incidence of bronchopulmonary cancer is very high and its prognosis is poor at an advanced stage. The evaluative role of CT and biopsy guidance has given it a place of choice in its management. The diagnosis of certainty remains histology. more...

We used a protein microarray featuring Plasmodium falciparum field variants of a merozoite surface antigen to examine malaria exposure in Malian children with different severe malaria syndromes. Unlike children with cerebral malaria alone or severe malarial anemia alone, those with concurrent cerebral malaria and severe malarial anemia had serologic responses demonstrating a broader prior parasite exposure pattern than matched controls with uncomplicated disease. Comparison of levels of malaria-related cytokines revealed that children with the concurrent phenotype had elevated levels of interleukin (IL)-6, IL-8, and IL-10. Our results suggest that the pathophysiology of this severe subtype is unique and merits further investigation. more...

var genes encode Plasmodium falciparum erythrocyte membrane protein-1 (PfEMP1) antigens. These highly diverse antigens are displayed on the surface of infected erythrocytes and play a critical role in immune evasion and sequestration of infected erythrocytes. Studies of var expression using non-leukocyte-depleted blood are challenging because of the predominance of host genetic material and lack of conserved var segments. Our goal was to enrich for parasite RNA, allowing de novo assembly of var genes and detection of expressed novel variants. We used two overall approaches: (i) enriching for total mRNA in the sequencing library preparations and (ii) enriching for parasite RNA with a custom capture array based on Roche’s SeqCap EZ enrichment system. The capture array was designed with probes based on the whole 3D7 reference genome and an additional >4,000 full-length var gene sequences from other P. falciparum strains. We tested each method on RNA samples from Malian children with severe or uncomplicated malaria infections. All reads mapping to the human genome were removed, the remaining reads were assembled de novo into transcripts, and from these, var-like transcripts were identified and annotated. The capture array produced the longest maximum length and largest numbers of var gene transcripts in each sample, particularly in samples with low parasitemia. Identifying the most-expressed var gene sequences in whole-blood clinical samples without the need for extensive processing or generating sample-specific reference genome data is critical for understanding the role of PfEMP1s in malaria pathogenesis. IMPORTANCE Malaria parasites display antigens on the surface of infected red blood cells in the human host that facilitate attachment to blood vessels, contributing to the severity of infection. These antigens are highly variable, allowing the parasite to evade the immune system. Identifying these expressed antigens is critical to understanding the development of severe malarial disease. However, clinical samples contain limited amounts of parasite genetic material, a challenge for sequencing efforts further compounded by the extreme diversity of the parasite surface antigens. We present a method that enriches for these antigen sequences in clinical samples using a custom capture array, requiring minimal processing in the field. While our results are focused on the malaria parasite Plasmodium falciparum, this approach has broad applicability to other highly diverse antigens from other parasites and pathogens such as those that cause giardiasis and leishmaniasis. more...

Background An effective vaccine against Plasmodium falciparum, the most common and deadly cause of malaria, is a global priority. Circumsporozoite protein (CSP) is a major P. falciparum vaccine target. Previously recognized CSP epitopes include the immunodominant NANP repeat region, the conserved junction between Region 1 (R1) and the NANP repeats, and the polymorphic Th2R and Th3R in the C-terminus. RTS,S, the most advanced vaccine to date, contains 19 NANP repeats and the C-terminus from the 3D7 parasite clone. CSP-specific monoclonal antibodies to the R1-NANP junctional region showed potent neutralizing activity in vitro and in vivo and are therefore under development for immunoprophylaxis. However, little is known about naturally acquired humoral immunity to precise and diverse epitopes along the CSP sequence, especially in the R1-NANP junctional region. Our goal was to use novel high-throughput tools to examine immunity to diverse CSP epitopes. Methods We probed sera from 10 adults and 10 children from Bandiagara, Mali, a region with intense, seasonal malaria transmission, on a diversity-reflecting peptide microarray. This microarray included 73 CSP variants from reference genomes and field-derived genomic data represented as 16 amino acid (aa) peptides with 12 aa overlap. We used a sliding window-based average smoothing procedure to determine log2 transformed signal intensities (SI) at each aa position. SI and serorecognition, defined as SI >2.5 standard deviations above the mean SI of malaria-naïve controls, were compared. We used the Wilcoxon rank-sum test for comparisons between adults and children and the Wilcoxon signed-rank test for matched comparisons of children over the malaria season, with the Benjamini-Hochberg procedure to control the false discovery rate. Results Adult sera recognized more variants than children at 313 of the 401 positions along CSP, including areas of the R1-NANP junctional region, the NANP repeat region, and the C-terminal Th2R and Th3R epitopes. Adults had higher SI than children to variants in known epitopes, including the R1-NANP junctional region and NANP, but not to a large portion of the 3D7 sequence of Th2R. Across the malaria season, children did not recognize significantly more variants at any one position. However, children had higher SI mid-season when compared with pre-season at a few small epitopes in the R1-NANP junctional region and Th2R. No significant differences existed between SI at any position when comparing post- to mid- or pre-season. Conclusions We identified precise CSP epitopes where serologic responses differed between adults and children and in children over a malaria season in Bandiagara. Adults showed responses to more variants and higher antibody responses at the R1-NANP junctional region and the NANP repeat region, but not to the 3D7 variant sequence in the Th2R epitope, which is included in RTS,S. Children acquired some short-lived immunity to the R1-NANP junctional region and a Th2R epitope during the season but not the NANP repeat region. Our limitations included a small sample size. Next steps include differentiation of immunodominant from protective responses in a larger study with longitudinal infection surveillance data. more...

Following Plasmodium falciparum infection, individuals can remain asymptomatic, present with mild fever in uncomplicated malaria cases, or show one or more severe malaria symptoms. Several studies have investigated associations between parasite transcription and clinical severity, but no broad conclusions have yet been drawn. Here, we apply a series of bioinformatic approaches based on P. falciparum’s tightly regulated transcriptional pattern during its ~48-hour intraerythrocytic developmental cycle (IDC) to publicly available transcriptomes of parasites obtained from malaria cases of differing clinical severity across multiple studies. Our analysis shows that within each IDC, the circulation time of infected erythrocytes without sequestering to endothelial cells decreases with increasing parasitaemia or disease severity. Accordingly, we find that the size of circulating infected erythrocytes is inversely related to parasite density and disease severity. We propose that enhanced adhesiveness of infected erythrocytes leads to a rapid increase in parasite burden, promoting higher parasitaemia and increased disease severity., To understand malaria symptoms, several studies investigate association between parasite’s transcriptome and disease severity. Here, Thomson-Luque et al. reanalyze available transcriptomic data of P. falciparum and find that longer circulation of infected erythrocytes without sequestering to endothelial cells associates with decreasing parasitaemia and less severe disease. more...

Vector-borne pathogens cause many human infectious diseases and are responsible for high mortality and morbidity throughout the world. They can also cause livestock epidemics with dramatic social and economic consequences. Due to its high costs, vector-borne disease surveillance is often limited to current threats, and the investigation of emerging pathogens typically occurs after the reports of clinical cases. Here, we use high-throughput sequencing to detect and identify a wide range of parasites and viruses carried by mosquitoes from Cambodia, Guinea, Mali and the USA. We apply this approach to individual Anopheles mosquitoes as well as pools of mosquitoes captured in traps; and compare the outcomes of this assay when applied to DNA or RNA. We identified known human and animal pathogens and mosquito parasites belonging to a wide range of taxa, as well as DNA sequences from previously uncharacterized organisms. Our results also revealed that analysis of the content of an entire trap could be an efficient approach to monitor and identify rare vector-borne pathogens in large surveillance studies. Overall, we describe a high-throughput and easy-to-customize assay to screen for a wide range of pathogens and efficiently complement current vector-borne disease surveillance approaches., Summary: We describe a surveillance technique enabling the detection of known and previously uncharacterized pathogens present in mosquitoes. This approach could reduce the costs of vector-borne disease monitoring and provide early warning of emerging diseases. more...

The gut microbiota has recently been associated with susceptibility/resistance to malaria in animal models and humans, yet the impact of the gut microbiota on the risk of a malaria attack remains to be assessed. This study aims at assessing the influence of the gut microbiota on malaria attacks and Plasmodium parasitæmia in children living in a malaria-endemic area in Mali. Three hundred healthy children were included in a 16-months cohort study in Bandiagara. Their gut bacteria and fungi community structures were characterised via 16S and ITS metabarcoding from stool samples collected at inclusion. Clinician team monitored the occurrence of malaria attacks. Asymptomatic carriage of Plasmodium was assessed by qPCR. Over the 16-month period, 107 (36%) children experienced at least one occurrence of malaria attacks, and 82 (27%) at least one asymptomatic Plasmodium parasitæmia episode. A higher gut bacteria richness was independently associated with susceptibility to asymptomatic parasitæmia episodes and malaria attacks; while the Shannon H diversity and Chao-1 richness index of gut fungi community structure was relatively homogeneous in children who were and were not infected with P. falciparum. Using a linear discriminant effect size analysis of operational taxonomic units assigned to the species level, 17 bacteria, including Clostridiaceae, Eubacteriaceae, Senegalimassilia sp., Atopobiaceae and Lachnosipraceae, and seven fungi, including Dioszegia fristigensis, Ogataea polymorpha and Cutaneotrichosporon cyanovorans, were associated with susceptibility; whereas eight bacteria, including, Bifidobacterium spp., Weissela confusa and Peptostreptococcacea, and 3 fungi, Malassezia sp., Niesslia exosporoides, and Didymocrea leucaenae, were associated with resistance to malaria. Moreover, 15 bacteria, including Coproccus eutactus, Terrisporobacter petrolearius, Klebsiella pneumoniae and Ruminococcaceae, and 13 fungi, including Wallemia mellicola, were associated with susceptibility, whereas 19 bacteria, including Bifidobacterium spp., Bacteroides fragilis, Peptostreptococcacea, and Lactobacillus ruminis, and three fungi, including Cryptococcus neoformans, were associated with resistance to asymptomatic Plasmodium parasitæmia episodes. Further studies are needed to confirm these findings that point the way towards strategies aiming to reduce the risk of malaria by modulating gut microbiota components in at-risk populations. more...

Vector-borne pathogens cause many human infectious diseases and are responsible for high mortality and morbidity throughout the world. They can also cause livestock epidemics with dramatic social and economic consequences. Due to the high costs, vector-borne disease surveillance is often limited to current threats, and the investigation of emerging pathogens typically occur after the reports of clinical cases. Here, we use high-throughput sequencing to detect and identify a wide range of parasites and viruses carried by mosquitoes from Cambodia, Guinea, Mali and Maryland. We apply this approach to individual Anopheles mosquitoes as well as pools of mosquitoes captured in traps; and compare the outcomes of this assay when applied to DNA or RNA. We identified known human and animal pathogens and mosquito parasites belonging to a wide range of taxa, insect Flaviviruses, and novel DNA sequences from previously uncharacterized organisms. Our results also revealed that analysis of the content of an entire trap is an efficient approach to monitor and identify potential vector-borne pathogens in large surveillance studies, and that analyses of RNA extracted from mosquitoes is preferable, when possible, over DNA-based analyses. Overall, we describe a flexible and easy-to-customize assay that can provide important information for vector-borne disease surveillance and research studies to efficiently complement current approaches. more...

Background Anopheles species identification is essential for an effective malaria vector control programme. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has been developed to identify adult Anopheles species, using the legs or the cephalothorax. The protein repertoire from arthropods can vary according to compartment, but there is no general consensus regarding the anatomic part to be used. Methods To determine the body part of the Anopheles mosquitoes best suited for the identification of field specimens, a mass spectral library was generated with head, thorax with wings and legs of Anopheles gambiae, Anopheles arabiensis and Anopheles funestus obtained from reference centres. The MSL was evaluated using two independent panels of 52 and 40 An. gambiae field-collected in Mali and Guinea, respectively. Geographic variability was also tested using the panel from Mali and several databases containing added specimens from Mali and Senegal. Results Using the head and a database without specimens from the same field collection, the proportion of interpretable and correct identifications was significantly higher than using the other body parts at a threshold value of 1.7 (p Conclusions The using of the head of Anopheles may improve the performance of MALDI-TOF MS. Region-specific mass spectrum databases will have to be produced. Further research is needed to improve the standardization in order to share online spectral databases. more...

Small mammals are the natural reservoirs for many zoonotic pathogens. Using molecular tools, we assessed the prevalence of bacteria and protozoans in small mammals and their ectoparasites in Faladje, Bougouni, and Bamoko, Mali. A total of 130 small mammals belonging to 10 different species were captured, of which 74 (56.9%) were infested by ectoparasites, including Laelaps echidnina, Xenopsylla cheopis, Amblyomma variegatum, Rhipicephalus sanguineus sensu lato, and Haemaphysalis spp. nymphs. DNA of Bartonella was found in 14/75 (18.7%), 6/48 (12.5%), and 3/7 (42.8%) small mammals from Faladje, Bougouni, and Bamako, respectively. In Faladje, Bartonella DNA was detected in 31/68 (45.6%) of L. echidnina and 14/22 (63.6%) of X. cheopis. In Bougouni, it was found in 2/26 (7.7%) of L. echidnina and 10/42 (23.8%) of X. cheopis. The sequences of Bartonella obtained from small mammals were close to those of Bartonella mastomydis, Bartonella elizabethae, and uncultured Bartonella spp. In Faladje, Coxiella burnetii DNA was detected in 64.4% (29/45) of Haemaphysalis spp. ticks, 4.5% (2/44) of Mastomys erythroleucus, 12.5% (1/8) of Praomys daltoni, and 1.5% (1/68) of L. echidnina. We found DNA of Wolbachia in X. cheopis from Faladje and DNA of Rickettsia africae and Ehrlichia ruminantium in Am. variegatum from Bougouni. The results of our study show that several small mammal species harbor and may serve as potential reservoirs of Bartonella spp., likely to play a major role in the maintenance, circulation, and potential transmission of bacteria in Mali. The pathogenicity of these bacteria for humans or animals remains to be demonstrated. more...

BackgroundEvaluation of local transmission epidemiology to characterize malaria risk is essential for planning malaria control and elimination programmes. The use of geographical information systems (GIS) has been a major asset to this approach. This study aimed to characterize the local spatio-temporal pattern of malaria infection and clinical disease after implementation of Seasonal Malaria Chemoprevention (SMC) and Indoor Residual Spraying (IRS) in Bandiagara, a Malian town.MethodsFrom October 2017 to December 2018, an active and passive surveillance system was established in a cohort study of three hundred children aged from 6 months to 15 years old. Weekly time-series of clinical malaria and monthly time-series of asymptomatic Plasmodium carriage and rainfall were plotted. Numbers of clinical malaria episodes and asymptomatic parasite carriers were mapped using Quantum Geographic Information System (QGIS). Landscape features of Bandiagara were obtained from Google earth. Clusters of high or low risk were identified under SaTScan® software using a Bernoulli model. ResultsFrom October 2017 to December 2018, 167 clinical malaria cases were recorded, mostly from July to December, while asymptomatic parasite carriage was observed during the entire study period. Three clusters of clinical episodes were found. All were hotspots. They were located in the north-east, south and west. No low risk cluster was identified. Three significant high-risk clusters of asymptomatic parasite carriage were identified in the south, north-east and north. These clusters were located near standing water. ConclusionThis study confirms the seasonality of clinical malaria in Bandiagara. The continued presence of asymptomatic parasite carriers maintains malaria transmission. To advance malaria elimination, control strategies must also target hotspots of asymptomatic parasite carriage. There was a spatial heterogeneity of clinical and asymptomatic malaria. Despite the implementation of additional preventives strategies, the locations of high-risk clusters were stable. more...

Eukaryotic enteric pathogens (EEP) are a public health issue in tropical areas. Yet, their interactions with the gut mycobiota remain poorly understood. We conducted a cross-sectional study in Malian children to analyze the impact of EEP on the gut fungal community. EEP were assessed by qPCR and the gut mycobiota was characterized by ITS1-2 metabarcoding in stool samples collected from 296 children. The 100 controls, in whom no EEP was detected, were compared to: a) 196 children with ≥1 EEP; b) 91 with only Blastocystis; c) 35 with only Giardia intestinalis; and d) 12 with another ( more...

We show that dual RNA-seq from patient blood samples allows characterization of host/parasite interactions during malaria infections and can provide a solid framework to study the acquisition of antimalarial immunity, as well as the adaptations of P. falciparum to malaria-experienced hosts., Children are highly susceptible to clinical malaria, and in regions where malaria is endemic, their immune systems must face successive encounters with Plasmodium falciparum parasites before they develop immunity, first against severe disease and later against uncomplicated malaria. Understanding cellular and molecular interactions between host and parasites during an infection could provide insights into the processes underlying this gradual acquisition of immunity, as well as to how parasites adapt to infect hosts that are successively more malaria experienced. Here, we describe methods to analyze the host and parasite gene expression profiles generated simultaneously from blood samples collected from five consecutive symptomatic P. falciparum infections in three Malian children. We show that the data generated enable statistical assessment of the proportions of (i) each white blood cell subset and (ii) the parasite developmental stages, as well as investigations of host-parasite gene coexpression. We also use the sequences generated to analyze allelic variations in transcribed regions and determine the complexity of each infection. While limited by the modest sample size, our analyses suggest that host gene expression profiles primarily clustered by individual, while the parasite gene expression profiles seemed to differentiate early from late infections. Overall, this study provides a solid framework to examine the mechanisms underlying acquisition of immunity to malaria infections using whole-blood transcriptome sequencing (RNA-seq). IMPORTANCE We show that dual RNA-seq from patient blood samples allows characterization of host/parasite interactions during malaria infections and can provide a solid framework to study the acquisition of antimalarial immunity, as well as the adaptations of P. falciparum to malaria-experienced hosts. more...

Background The commensal microbiota of mosquitoes impacts their development, immunity, and competency, and could provide a target for alternative entomological control approaches. However, despite the importance of the mosquito/microbiota interactions, little is known about the relative contribution of genetic and non-genetic factors in shaping the bacterial communities of mosquitoes. Methods We used a high-throughput sequencing based assay to characterize the bacterial composition and diversity of 665 individual field-caught mosquitoes, as well as their species, genotype at an insecticide resistance locus, blood meal composition, and the eukaryotic parasites and viruses they carry. We then used these data to rigorously estimate the individual effect of each parameter on the bacterial diversity as well as their relative contribution to the microbial composition. Results Overall, multivariate analyses did not reveal any significant contribution of the mosquito species, insecticide resistance or blood meal to the bacterial composition of the mosquitoes surveyed. Infection with parasites and viruses only contributed very marginally and the main driver of the bacterial diversity was the location where each mosquito was collected which explained roughly 20% of the variance observed. Conclusions This analysis shows that, when confounding factors are taken into account, the sites where the mosquitoes are collected is the main driver of the bacterial diversity of wild-caught mosquitoes, although further studies will be needed to determine how the specific components of the local environment affecting the bacterial composition. more...

To prevent premature dismissal of promising vaccine programs, it is critical to determine if lack of efficacy in the field is due to allele specific-efficacy, rather than to the lack of immunogenicity of the candidate antigen. Here we use samples collected during a field trial of the AMA1-based FMP2.1/AS02A malaria vaccine, which incorporates the AMA1 variant encoded by the reference Plasmodium falciparum 3D7 strain, to assess the usefulness of epitope-based sieve analysis for the detection of vaccine-induced allele-specific immune responses. The samples used are from volunteers who received the malaria vaccine FMP2.1/AS02A or a control (rabies vaccine), during a vaccine efficacy field trial, and who later developed malaria. In a previous study, P. falciparum DNA was extracted from all samples, and the ama1 locus amplified and sequenced. Here, a sieve analysis was used to measure T and B-cell escape, and difference in 3D7-like epitopes in the two treatment arms. Overall, no difference was observed in mean amino acid distance to the 3D7 AMA1 variant between sequences from vaccinees and controls in B-cell epitopes. However, we found a significantly greater proportion of 3D7-like T-cell epitopes that map to the AMA1 cluster one loop (c1L) region in the control vs. the vaccinee group (p = 0.02), consistent with allele-specific vaccine efficacy. Interestingly, AMA1 epitopes in infections from vaccinees had higher mean IC50, and consequently lower binding affinity, than epitopes generated from the control group (p = 0.01), suggesting that vaccine-induced selection impacted the immunological profile of the strains that pass through the sieve imposed by the vaccine-induced protection. These findings are consistent with a vaccine-derived sieve effect on the c1L region of AMA1 and suggest that sieve analyses of malaria vaccine trial samples targeted to epitopes identified in silico can help identify protective malaria antigens that may be efficacious if combined in a multivalent vaccine. more...

Circumsporozoite protein (CSP) coats the Plasmodium falciparum sporozoite surface and is a major malaria subunit vaccine target. We measured epitope-specific reactivity to field-derived CSP haplotypes in serum samples from Malian adults and children on a custom peptide microarray. Compared to children, adults showed greater antibody responses and responses to more variants in regions proximal to and within the central repeat region. Children acquired short-lived immunity to an epitope proximal to the central repeat region but not to the central repeat region itself. This approach has the potential to differentiate immunodominant from protective epitope-specific responses when combined with longitudinal infection data. more...

BackgroundDeclines in malaria incidence attributed to the implementation of control strategies have been reported in many African countries. The declines are often accompanied by a shift in clinical burden to older children. In Mali, artemisinin-based combination therapy (ACT) was introduced in 2004, and Long-lasting insecticide-treated nets (LLINs) have been partially distributed free of charge since 2007. In Bandiagara, a study conducted from 2009 to 2013 showed a stable incidence of malaria compared to 1999 despite the use of ACTs and LLINs. Since 2016, seasonal malaria chemoprevention (SMC) has been scaled up across the country. In addition to these strategies, the population of Bandiagara benefited the universal bed net coverage and indoor residual spray (IRS) implementation in 2017 and 2018.This study aimed to measure the incidence of malaria in the context of recent scaling-up of control strategies.MethodsA cohort of 300 children aged 6 months to 15 years was followed from October 2017 to December 2018 in Mali. Monthly cross-sectional surveys were done to measure the prevalence of malaria infection by microscopy and anaemia. The study outcomes included the monthly prevalence of malaria infection and the incidence of symptomatic malaria.ResultsThe incidence of symptomatic malaria was 0.5 episodes/person-year. The average prevalence of malaria parasitaemia was 6.7%. The incidence was higher in the oldest age group than the youngest one (0.6 episodes/person-year in children above 10 years vs 0.29 in 6 months to 5 years age group).ConclusionsThis study showed a reduction of malaria incidence compared to 1999 and 2009-2013. An age shift in the susceptibility to malaria was also observed; older children experienced more clinical malaria than younger ones. These findings suggest to extend malaria control efforts to older children. more...

Variant surface antigens (VSAs) play a critical role in severe malaria pathogenesis. Defining gaps, or “lacunae”, in immunity to these Plasmodium falciparum antigens in children with severe malaria would improve our understanding of vulnerability to severe malaria and how protective immunity develops. Using a protein microarray with 179 antigen variants from three VSA families as well as more than 300 variants of three other blood stage P. falciparum antigens, reactivity was measured in sera from Malian children with cerebral malaria or severe malarial anaemia and age-matched controls. Sera from children with severe malaria recognized fewer extracellular PfEMP1 fragments and were less reactive to specific fragments compared to controls. Following recovery from severe malaria, convalescent sera had increased reactivity to certain non-CD36 binding PfEMP1s, but not other malaria antigens. Sera from children with severe malarial anaemia reacted to fewer VSAs than did sera from children with cerebral malaria, and both of these groups had lacunae in their seroreactivity profiles in common with children who had both cerebral malaria and severe malarial anaemia. This microarray-based approach may identify a subset of VSAs that could inform the development of a vaccine to prevent severe disease or a diagnostic test to predict at-risk children. more...

Visceral leishmaniasis (VL) is the most serious form of human leishmaniasis. VL is understudied in West Africa. The increasing number of patients at-risk, including persons living with HIV and other chronic immunosuppressive diseases, and likely underreporting of VL related to diagnostic challenges advocate for review of existing data to understand VL regional epidemiology. Our review aims to describe the clinical characteristics and epidemiology of Human VL (HVL) in West Africa. We conducted a literature search to identify peer-reviewed articles and grey literature sources using the search terms “Visceral leishmaniasis West Africa”, “Leishmania donovani West Africa”; and “Leishmania infantum West Africa”. Thirty published articles report HVL from seven countries, including The Gambia, Niger, Nigeria, Ivory Coast, Togo, Burkina Faso, and Guinea Bissau. Three countries report cases of Canine Visceral Leishmaniasis (CVL), including The Gambia, Senegal, and Burkina Faso. Niger, Nigeria, and Ivory Coast report the greatest number of HVL cases. As VL is present in West Africa, active surveillance, increased diagnostic capacity, and studies of vectors and reservoirs are essential to better understand VL epidemiology in the region. more...

Background A malaria vaccine based on Plasmodium falciparum apical membrane antigen 1 (AMA1) elicited strain specific efficacy in Malian children that waned in the second season after vaccination despite sustained AMA1 antibody titers. With the goal of identifying a humoral correlate of vaccine-induced protection, pre- and post-vaccination sera from children vaccinated with the AMA1 vaccine and from a control group that received a rabies vaccine were tested for AMA1-specific immunoglobulin G (IgG) subclasses (IgG1, IgG2, IgG3, and IgG4) and for antibody avidity. Methods Samples from a previously completed Phase 2 AMA1 vaccine trial in children residing in Mali, West Africa were used to determine AMA1-specific IgG subclass antibody titers and avidity by ELISA. Cox proportional hazards models were used to assess correlation between IgG subclass antibody titers and risk of time to first or only clinical malaria episode and risk of multiple episodes. Asexual P. falciparum parasite density measured for each child as area under the curve were used to assess correlation between IgG subclass antibody titers and parasite burden. Results AMA1 vaccination did not elicit a change in antibody avidity; however, AMA1 vaccinees had a robust IgG subclass response that persisted over the malaria transmission season. AMA1-specific IgG subclass responses were not associated with decreased risk of subsequent clinical malaria. For the AMA1 vaccine group, IgG3 levels at study day 90 correlated with high parasite burden during days 90–240. In the control group, AMA1-specific IgG subclass rise and persistence over the malaria season was modest and correlated with age. In the control group, titers of several IgG subclasses at days 90 and 240 correlated with parasite burden over the first 90 study days, and IgG3 at day 240 correlated with parasite burden during days 90–240. Conclusions Neither IgG subclass nor avidity was associated with the modest, strain-specific efficacy elicited by this blood stage malaria vaccine. Although a correlate of protection was not identified, correlations between subclass titers and age, and correlations between IgG subclass titers and parasite burden, defined by area under the curve parasitaemia levels, were observed, which expand knowledge about IgG subclass responses. IgG3, known to have the shortest half-life of the IgG subclasses, might be the most temporally relevant indicator of ongoing malaria exposure when examining antibody responses to AMA1. Electronic supplementary material The online version of this article (10.1186/s12936-019-2637-x) contains supplementary material, which is available to authorized users. more...

Malaria has been a major driving force in the evolution of the human genome. In sub-Saharan African populations, two neighbouring polymorphisms in the Complement Receptor One (CR1) gene, named Sl2 and McCb, occur at high frequencies, consistent with selection by malaria. Previous studies have been inconclusive. Using a large case-control study of severe malaria in Kenyan children and statistical models adjusted for confounders, we estimate the relationship between Sl2 and McCb and malaria phenotypes, and find they have opposing associations. The Sl2 polymorphism is associated with markedly reduced odds of cerebral malaria and death, while the McCb polymorphism is associated with increased odds of cerebral malaria. We also identify an apparent interaction between Sl2 and α+thalassaemia, with the protective association of Sl2 greatest in children with normal α-globin. The complex relationship between these three mutations may explain previous conflicting findings, highlighting the importance of considering genetic interactions in disease-association studies., eLife digest Malaria kills more than half a million children in Africa every year. The disease is caused by the Plasmodium falciparum parasite, and mosquitos infected with the parasites spread them to humans when they bite. Once inside a human, the parasites infect the red blood cells. In severe cases, these red blood cells can stick to the walls of small blood vessels that supply the brain and so hinder the flow of oxygen, causing a coma. This is called cerebral malaria. Malaria can also result in the destruction of many oxygen-carrying red blood cells, which causes severe anemia. Both cerebral malaria and severe anemia can lead to death. Small changes (called mutations) in certain human genes can protect against malaria. Over time, mutations that protect people living in Africa from dying from malaria have been passed down through generations. A good example is the sickle cell mutation, which causes red blood cells to be of an unusual shape, but also affects the ability of malaria parasites to grow normally within red cells. Finding new mutations that protect against malaria may help scientists understand how severe malaria happens and eventually develop new drugs and vaccines against the disease. Some studies have found that mutations in a gene called complement receptor 1 (CR1) may be protective, although others have disagreed. Now, Opi, Swann et al. show that children with one of the CR1 mutations were one-third less likely to get cerebral malaria and half as likely to die as children without the mutation. In the study, genetic and health information on more than 5,500 children in Kenya were analyzed to see if the severity of malaria differed depending on whether they had a CR1 mutation. They also found that the CR1 mutation is only protective against severe malaria when the child does not have another malaria- protective mutation called α-thalassemia. In children with α-thalassemia, the CR1 mutation does not make a difference. The interaction between the CR1 mutation and α-thalassemia may explain why some studies did not show a benefit of CR1. If the researchers did not include α-thalassemia in their assessment, they could not have seen the whole picture. Future studies showing how the CR1 mutation protects against cerebral malaria could help identify new treatments that prevent severe disease or death. More study of interactions between genes that play a role in malaria may also be helpful. more...

ResumeAu Mali la leishmaniose cutanee (LC) est bien decrite en milieu rural, mais sa transmission n’est pas encore etablie en milieu urbain. L’objectif de l’etude etait de decrire la faune phlebotomienne a Bamako et dans ses environs. Les pieges CDC et adhesifs servaient a collecter les phlebotomes en 2011 et 2012 a Bamako. Les pieges etaient places dans le district de Bamako repartis en 30 zones (200 m × 200 m) a l’aide des images de satellite SPOT-5. La delimitation des zones etait basee sur les facteurs ecologiques (relief, hydrographie, couverture vegetale) et anthropologiques (nature des maisons, depots d’ordure). Les pieges etaient places en 2011 a Sotuba, zone periurbaine, puis a Doneguebougou et Banambani, deux villages environnants de Bamako. Au total 122 phlebotomes etaient collectes 27 (22,13 %) a Banambani, 12 (9,83 %) a Doneguebougou, 2 (1,63 %) a Sotuba et 81 (66,39 %) a Bamako. La densite des phlebotomes en novembre etait plus elevee, avec 48 specimens captures (39,3 %), que celle d’avril, ... more...

The objective of this work was to describe the epidemiology of schistosomiasis 10 years after mass administration of praziquantel began in Sotuba, Mali.This observational cross-sectional survey in Sotuba, a periurban village in the Bamako district, took place from July to September 2010 and collected stool and urine samples from residents at least one year old. Kato-Katz (for stool) and urine filtration techniques were used to detect Schistosoma mansoni and S. hæmatobium eggs, respectively. Overall, 335 urine samples and 300 stool samples were examined. The prevalence rate was 5.4% (18/335) for S. hæmatobium and 8.7% (26/300) for S. mansoni. Excretion of these eggs was most frequent in the 6-15 year-old group: 4.8% (16/335) for S. hæmatobium and 7.7% (23/300) for S. mansoni. Snails of the Biomphalaria pfeifferi and Bulinus truncatus species were the intermediate hosts, captured in the fields at water contact points. The principal clinical symptoms reported by participants were abdominal pain 27.2% (61/169) and headaches 23.2% (52/169).Despite the implementation of mass drug administration in Mali a decade ago, our results show that schistosomiasis transmission continues in Sotuba. Assessment of the risk factors for this persistent transmission is strongly needed. more...

Sickle hemoglobin trait protects against severe and uncomplicated Plasmodium falciparum malaria [1–3], but at a cost, in that hemoglobin (Hb) SS disease is associated with significant morbidity and mortality [4]. In contrast, hemoglobin C trait, which is primarily found in West Africa [5], appears to offer protection against severe malaria [6], but hemoglobin CC disease does not have the degree of morbidity and mortality associated with hemoglobin SS disease [7]. Early work demonstrating the protective effects of hemoglobin C trait against severe malaria involved studies of the predominantly Dogon population in east-central Mali [8]. Subsequently, a case-control study in Burkina Faso found that hemoglobin C trait may be protective against both severe and uncomplicated forms of malaria in children [9]. In contrast, a recent longitudinal study of children less than 2 years of age in Ghana found that hemoglobin S trait protected against uncomplicated malaria and anemia (hemoglobin more...

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been recently described as an innovative and effective tool for identifying arthropods and mosquito blood meal sources. To test this approach in the context of an entomological survey in the field, mosquitoes were collected from five ecologically distinct areas of Mali. We successfully analysed the blood meals from 651 mosquito abdomens crushed on Whatman filter paper (WFPs) in the field using MALDI-TOF MS. The legs of 826 mosquitoes were then submitted for MALDI-TOF MS analysis in order to identify the different mosquito species. Eight mosquito species were identified, including Anopheles gambiae Giles, Anopheles coluzzii, Anopheles arabiensis, Culex quinquefasciatus, Culex neavei, Culex perexiguus, Aedes aegypti and Aedes fowleri in Mali. The field mosquitoes for which MALDI-TOF MS did not provide successful identification were not previously available in our database. These specimens were subsequently molecularly identified. The WFP blood meal sources found in this study were matched against human blood (n = 619), chicken blood (n = 9), cow blood (n = 9), donkey blood (n = 6), dog blood (n = 5) and sheep blood (n = 3). This study reinforces the fact that MALDI-TOF MS is a promising tool for entomological surveys. more...

International audience; These authors contributed equally to this work. Abstract. In areas of seasonal malaria transmission, the incidence rate of malaria infection is presumed to be near zero at the end of the dry season. Asymptomatic individuals may constitute a major parasite reservoir during this time. We conducted a longitudinal analysis of the spatio-temporal distribution of clinical malaria and asymptomatic parasitemia over time in a Malian town to highlight these malaria transmission dynamics. For a cohort of 300 rural children followed over 2009–2014, periodicity and phase shift between malaria and rainfall were determined by spectral analysis. Spatial risk clusters of clinical episodes or carriage were identified. A nested-case-control study was conducted to assess the parasite carriage factors. Malaria infection persisted over the entire year with seasonal peaks. High transmission periods began 2–3 months after the rains began. A cluster with a low risk of clinical malaria in the town center persisted in high and low transmission periods. Throughout 2009–2014, cluster locations did not vary from year to year. Asymptomatic and gametocyte carriage were persistent, even during low transmission periods. For high transmission periods, the ratio of asymptomatic to clinical cases was approximately 0.5, but was five times higher during low transmission periods. Clinical episodes at previous high transmission periods were a protective factor for asymptomatic carriage, but carrying parasites without symptoms at a previous high transmission period was a risk factor for asymptomatic carriage. Stable malaria transmission was associated with sustained asymptomatic carriage during dry seasons. Control strategies should target persistent low-level parasitemia clusters to interrupt transmission. more...

Plasmodium vivax was thought to infect only the erythrocytes of Duffy blood group positive people. In the last decade, P. vivax has appeared throughout Africa, both in areas where Duffy positive and negative people live side by side as in Madagascar and Ethiopia and in areas where people are primarily Duffy negative, such as in western Kenya. We performed quantitative polymerase chain reaction on blood samples dried onto filter paper to determine the prevalence of P. vivax and Plasmodium falciparum in a cohort of 300 children (newborn to 6 years of age) in Bandiagara, a Sahelian area of Mali, west Africa, where the people are Duffy negative. We report 1-3 occurrences of P. vivax in each of 25 Duffy-negative children at six time points over two rainy seasons and the beginning of the third season. The prevalence of P. vivax infection was 2.0-2.5% at every time point (June 2009 to June 2010). All children with P. vivax infections were asymptomatic and afebrile, and parasite densities were extremely low. Anemia, however, was the main burden of infection. Plasmodium vivax could become a burden to sub-Saharan Africa, and the evidence of P. vivax existence needs to be taken into consideration in designing malaria control and elimination strategies in Africa. more...

BackgroundMalaria remains a leading cause of child mortality in sub-Saharan Africa. Severe malaria is the main pathway to death caused by malaria. A study of factors associated with protection against severe malaria is best achieved using a case-control design. However, these studies are affected by the quality and appropriateness of the choice of controls that may introduce important bias in study design and definitively alter the conclusions from the studies. It is of paramount importance that the presence or absence of an episode of severe malaria in the history of the controls is ascertained. In settings with reliable medical data this is easily tracked back from hospital records. In settings like Bandiagara, with weak health care systems, a dedicated approach is needed to track history of severe malaria. We used an adapted verbal autopsy questionnaire to identify presence of cerebral malaria in the history of controls in a case-control study of severe malaria in Bandiagara.We have assessed the sensitivity, specificity and predictive positive and negative values of the questionnaire.MethodsFrom January through August 2018 we enrolled 450 children with or without known confirmed cerebral malaria selected at health care centers in Bandiagara and Bamako, with archived medical records. Parents of enrolled children were identified, located and interviewed using the adapted verbal autopsy questionnaire. Interviewers were not aware of children’s diagnosis. We compared the diagnosis derived from the verbal autopsy questionnaire to the confirmed biological diagnosis from the medical records.ResultsWe will present full results on the sensitivity, specificity, the predictive positive and negative values of the verbal questionnaire, and the Kappa coefficient of agreement.ConclusionA good verbal questionnaire will enhance the quality of the choice of controls in case-control studies of severe malaria and overall will improve the quality and relevance of inferences from such studies. more...