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Background: Cytochrome P450 (CYP) enzymes are essential in the metabolism of most drugs used today. Single nucleotide polymorphism(s) occurring in CYP genes can adversely affect drug pharmacokinetics, efficacy, and safety. Individuals carrying the CYP2C8*2 c.805A > T (CYP2C8*2; rs11572103) allele have impaired amodiaquine metabolism, increased risk of amodiaquine-related adverse events, and may promote the selection of drug-resistant parasite strains. This study investigated the distribution of the CYP2C8*2 allele in Brazzaville, Republic of Congo, where artesunate + amodiaquine is used as the second-line treatment for uncomplicated Plasmodium falciparum malaria. Methods: A total of 285 febrile children visiting the Marien Ngouabi paediatric hospital were genotyped for CYP2C8*2 using PCR-restriction fragment length polymorphism (PCR-RFLP). The allele frequencies and genotype distribution were determined. Results: The CYP2C8*2 allele was successfully genotyped in 75% (213/285) of the study participants. The CYP2C8*2A allele had a frequency of 63%, whereas the CYP2C8*2T allele had a frequency of 37%. Genotypes CYP2C8*2AA (rapid metabolizer), CYP2C8*2AT (intermediate metabolizer), and CYP2C8*2TT (poor metabolizer) were observed in 44%, 38%, and 18% of the investigated participants, respectively. Conclusions: This study gives the first description of CYP2C8*2 allele distribution in the Republic of Congo and highlights the potential risk of amodiaquine-related adverse events. Information from this study will be beneficial during pharmacovigilance investigations. Keywords: Cytochrome P450, CYP2C8, Brazzaville, Republic of Congo, Pharmacogenetics

Background Malaria in pregnancy is associated with considerable morbidity and mortality. Regular surveillance of artemisinin-based combination therapy tolerance, or molecular makers of resistance, is vital for effective malaria treatment, control and eradication programmes. Plasmodium falciparum multiple drug resistance-1 gene (Pfmdr1) N86Y mutation is associated with reduced susceptibility to lumefantrine. This study assessed the prevalence of Pfmdr1 N86Y in Brazzaville, Republic of Congo. Methods A total 1001 of P. falciparum-infected blood samples obtained from asymptomatic malaria pregnant women having a normal child delivery at the Madibou Integrated Health Centre were analysed. Pfmdr1 N86Y genotyping was conducted using PCR-restriction fragment length polymorphism. Results The wild type Pfmdr1 N86 allele was predominant (> 68%) in this study, whereas a few isolates carrying the either the mutant allele (Pfmdr1 86Y) alone or both alleles (mixed genotype). The dominance of the wildtype allele (pfmdr1 N86) indicates the plausible decline P. falciparum susceptibility to lumefantrine. Conclusion This study gives an update on the prevalence of Pfmdr1 N86Y alleles in Brazzaville, Republic of Congo. It also raises concern on the imminent emergence of resistance against artemether–lumefantrine in this setting. This study underscores the importance to regular artemether–lumefantrine efficacy monitoring to inform the malaria control programme of the Republic of Congo.

Background: Regular surveillance of artemisinin−based combination therapy tolerance or resistance molecular makers is vital for effective malaria treatment, control and eradication programmes. P. falciparum multiple drug resistance-1 gene (Pfmdr1) N86Y mutation is associated with reduced susceptibility to lumefantrine. This study assessed the prevalence of Pfmdr1 N86Y in Brazzaville, Republic of Congo. Methods: A total 1001 of P. falciparum−infected blood samples obtained from asymptomatic malaria pregnant women having a normal child delivery at the Madibou Integrated Health Center were analysed.Pfmdr1 N86Y genotyping was conducted using PCR-Restriction fragment length polymorphism (RFLP). Results: The wild type Pfmdr1 N86 allele was predominant (>68 %) in this study whereas a few isolates carrying the either the mutant allele (Pfmdr1 86Y) alone or both alleles (mixed genotype). The dominance of the wildtype allele (pfmdr1 N86) indicates the plausible decline P. falciparum susceptibility to lumefantrine. Conclusion: This study gives an update on the prevalence of Pfmdr1 N86Y alleles in Brazzaville, Republic of Congo. It also raises concern on the imminent emergence of resistance against artemether−lumefantrine in this setting. Our study underscores the importance to regular artemether−lumefantrine efficacy monitoring to inform malaria control programme of the Republic of Congo.

Kenya has, in the last decade, made tremendous progress in the fight against malaria. Nevertheless, continued surveillance of the genetic diversity and population structure of Plasmodium falciparum is required to refine malaria control and to adapt and improve elimination strategies. Twelve neutral microsatellite loci were genotyped in 201 P. falciparum isolates obtained from the Kenyan-Ugandan border (Busia) and from two inland malaria-endemic sites situated in western (Nyando) and coastal (Msambweni) Kenya. Analyses were done to assess the genetic diversity (allelic richness and expected heterozygosity, [He ]), multilocus linkage disequilibrium ( ISA ) and population structure. A similarly high degree of genetic diversity was observed among the three parasite populations surveyed (mean He = 0.76; P > 0.05). Except in Msambweni, random association of microsatellite loci was observed, indicating high parasite out-breeding. Low to moderate genetic structure (FST = 0.022-0.076; P

Background Malaria transmission-blocking anti-malarial drugs, such as primaquine, offers an effective strategy for reducing the incidence of falciparum malaria. However, this drug induces haemolytic anaemia among glucose-6-phosphate dehydrogenase (G6PD) deficient individuals. The distribution of G6PD deficiency in Brazzaville, Republic of Congo and the association of G6PD deficiency with haemoglobin levels and blood cell counts were investigated. Methods A total of 212 febrile children were recruited for this study. Plasmodium falciparum diagnosis was conducted by microscopy and nested PCR. Sanger sequencing was used to assess G6PD deficiency by detecting 202G>A (rs1050828) and 376A>G (rs1050829) single nucleotide polymorphisms. Results Two hundred and twelve children were successfully genotyped for G6PD variants. Overall, 13% (27/212) of the children were G6PD deficient and 25% (25/100) females were heterozygous (11 BA− and 14 A+A−). The remaining 160 children had a normal G6PD genotype. The mean red blood and mean platelet counts were significantly lower in hemizygous male (G6PD A−) participants than in normal male (G6PD A+ or B) participants (p

Mosquitoes are usually targeted using insecticides, insect growth regulators, and microbial agents. Indoor residual spraying and insecticide-treated bed nets. However, these strategies have negative effects on human health, the environment and induce resistance in a number of species. Eco-friendly tools have been recently implemented against mosquito vectors, including plant-based insecticides. To date few studies have adopted World Health Organization (WHO) Pesticide Evaluation Scheme guidelines for repellent testing against mosquitoes. This review presents a summary of recent information on development, and efficacy of plant-based repellents against Anopheles mosquitoes as well as promising new advances in the field. All eligible studies published up to April 2020 were systematically searched in several databases, namely PubMed/Medline, Scopus and Google scholar. The outcomes of interest were percentage repellency, protection time and additional properties identified in repellent compounds. A total of 27 trials met the inclusion criteria. The highest repellency effect against mosquitoes was conferred by citronella, followed by Ligusticum sinense extract, pine, Dalbergia sissoo, and Rhizophora mucronata oils with 100% protection for 8 to 14 hours. Furthermore, essential oils from plants such as lavender, camphor, catnip, geranium, jasmine, broad-leaved eucalyptus, lemongrass, lemon-scented eucalyptus, amyris, narrow-leaved eucalyptus, carotin, cedarwood, chamomile, cinnamon oil, juniper, cajeput, soya bean, rosemary, niaouli, olive, tagetes, violet, sandalwood, litsea, galbanum, and C. longa also showed >90% repellency within 8 hours against different species of Anopheles. Therefore, the review showed, essential oils and extracts of some plants could be formulated for the development of eco-friendly repellents against Anopheles species. Plant oils may serve as suitable alternatives to synthetic repellents in the future as they are relatively safe, inexpensive, and are readily available in many parts of the world.

Prompt diagnosis and appropriate treatment of malaria remain the hallmark for reducing malaria-related mortality in high transmission areas. Plasmodium falciparum histidine-rich protein2 (PfHRP2) based rapid diagnostic tests (RDT) play a vital role in prompt and accurate malaria diagnosis. However, pfhrp2 gene deletion threatens the RDT test sensitivity. This study reports the presence of pfhrp2 and pfhrp3 genes deletion among parasite isolates in Nigeria. Febrile children were screened using histidine-rich protein (HRP2) specific RDT (SD-Bioline RDT) and microscopy for P. falciparum infections. All RDT negative samples were re-evaluated by polymerase chain reaction (PCR). The presence of parasite in RDT false negative cases and randomly selected RDT positive cases were validated using PCRs targeting glutamate-rich protein (glurp) and merozoite surface proteins (msp-1 and msp-2). Thereafter, exon 2 of pfhrp2 and pfhrp3 were amplified, and Sanger sequenced. A total of 511 febrile children were enrolled out of which 309 (61%) were positive by RDT. The presence of pfhrp2 and pfhrp3 genes were analyzed in 66 PCR positive samples comprising of 31 RDT false negative and 35 RDT true positive randomly selected samples. The pfhrp2 and pfhrp3 genes failed to amplify in 17% (11/66) and 6% (4/66) samples, respectively. Seven of the eleven samples had only pfhrp2 deletion while four had both pfhrp2 and pfhrp3 deletions. The absence of the pfhrp2 gene may be responsible for the seven RDT false negative cases observed. Three RDT positive cases lacked pfhrp2 whereas pfhrp3 was absent in only four RDT false negative cases. The pfhrp2 and pfhrp3 amino acid repeat sequences were highly diverse. The P. falciparum isolates lacking pfhrp2 and pfhrp3 genes may be circulating and contributing to RDT false negativity in Nigeria. More studies in larger population and seasonally defined cases will be needed to determine the extent of pfhrp2/3 genes deletion in different geographical areas of Nigeria.

In PNAS, Demas et al. (1) show, by long-term in vitro selection using culture-adapted Plasmodium falciparum isolates from Senegal, that the gene encoding the actin-binding protein P. falciparum coronin ( pfcoronin ) and its genetic variants (G50E, R100K, and E107V) can reduce the susceptibility of the parasite to the active metabolite of the fast-acting antimalarial drug artemisinin, dihydroartemisinin (DHA). Resistance to artemisinins is a global threat in malaria control and elimination efforts (2). Artemisinin resistance, first reported in Southeast Asia and still extremely rare, was associated with the P. falciparum Pf Kelch13-propeller domain ( kelch13 mutations: Y493H, R539T, I543T, and C580Y) (3). Pf Coronin, which is structurally similar to … [↵][1]1To whom correspondence may be addressed. Email: velavan{at}medizin.uni-tuebingen.de. [1]: #xref-corresp-1-1

BackgroundThe inter-individual genetic polymorphism of cytochrome P450 enzymes (CYP), involved in the metabolism of many drugs, partly modulates drug response and toxicity. Single nucleotide polymorphisms of CYP2B6 for example, G516T have been implicated in high- and sub-therapeutic plasma concentration of the current antimalarial, HIV and TB first-line drugs in various geographical regions and thus undermines effective disease management. At present, there is no data on the frequency of CYP2B6 c.516G>T among the Congolese population, despite a significant number of people undergoing antimalarial, HIV and TB treatment that relies on CYP2B6-based drug clearance or activation.MethodsA total of 418 patients with HIV-1 mono-infection, HIV-1 +TB coinfection and P. falciparum infection were genotyped for CYP2B6 c.516G>T polymorphism using PCR-RFLP. The frequencies of the alleles as well as the genotypes (GG, GT and TT) were determined.ResultsThe frequency of CYP2B6 c.516G>T polymorphism was 69% and frequency of G and T alleles were 45% and 55%, respectively. 17.0% (49/288) of participants were GG (extensive metaboliser), 55.2% (159/288) of participants were GT (intermediate metaboliser) and 27.8% (80/288) of participants were TT (poor metabolisers).ConclusionThis study highlights CYP2B6 c.G516T polymorphism as a potential determinant of drug response and toxicity among the Congolese population, particularly those undergoing antiretroviral, malaria and tuberculosis treatment within the current first-line drug policy framework.

BackgroundMalaria remains a public health problem in Republic of the Congo. The sub-microscopic infection including gametocytaemia constitutes a parasite reservoir that is recognised to contribute to malaria transmission. It is known that primaquine, an 8-aminoquinoline, is effective to eliminate Plasmodium falciparum (Pf) gametocytes. However, it induces haemolytic anaemia in individuals with glucose-6-phosphate dehydrogenase deficiency (G6PDd). It has been reported G6PDd also confers protection against severe malaria. To know the prevalence of G6PDd in the Congolese population is important in the case of future utilisation of this drug in the country. Therefore, in this study, we investigated 1) the prevalence of G6PDd in children infected with Pf and 2) the possible association between the presence of malaria, the presence of G6PD mutation and haemoglobin concentration.Methods229 children aged 1 to 10 years old presenting with fever (axillary T°≥37.5°C) were enrolled at the paediatric hospital Marien Ngouabi in Brazzaville. Thick and thin blood smears were done to detect and identify malaria parasites and determine parasite density. To detect the different glucose-6-phosphate dehydrogenase genotypes, a 968 bp fragment of the G6PD gene containing the polymorphisms 202G&gt1;A and 376&gt1;G was amplified by PCR followed by sequencing.ResultsMalaria prevalence was 22 (10%). With regard to G6PD analysis, it was found that 206 patients had G6PD genotype available including 74.8% (154/206) with G6PD normal, 12.1% (25/206) with heterozygous genotypes and 13.1% (27/206) with G6PD deficiency [11.6% (24/206) were male hemizygous and 1.4% (3/206) were female homozygous]. Data are further analysed to investigate the association between G6PD genotype, uncomplicated malaria, haemoglobin concentration as well as parasite densities.ConclusionA high prevalence of G6PD deficiency is reported for these Congolese children. Further investigation with larger sample size in different areas of the country is needed to design future and adapted interventions.