Background Plasmodium falciparum transmission depends on mature gametocytes that can be ingested by mosquitoes taking a blood meal on human skin. Although gametocyte skin sequestration has long been hypothesized as important contributor to efficient malaria transmission, this has never been formally tested. Methods In naturally infected gametocyte carriers from Burkina Faso, we assessed infectivity to mosquitoes by direct skin feeding and membrane feeding. We directly quantified male and female gametocytes and asexual parasites in finger-prick and venous blood samples, skin biopsy samples, and in of mosquitoes that fed on venous blood or directly on skin. Gametocytes were visualized in skin tissue with confocal microscopy. Results Although more mosquitoes became infected when feeding directly on skin then when feeding on venous blood (odds ratio, 2.01; 95% confidence interval, 1.21–3.33; P = .007), concentrations of gametocytes were not higher in the subdermal skin vasculature than in other blood compartments; only sparse gametocytes were observed in skin tissue. Discussion Our data strongly suggest that there is no significant skin sequestration of P. falciparum gametocytes. Gametocyte densities in peripheral blood are thus informative for predicting onward transmission potential to mosquitoes and can be used to target and monitor malaria elimination initiatives.

Transmission of Plasmodium falciparum depends on the presence of mature gametocytes that can be ingested by mosquitoes taking a bloodmeal when feeding on human skin. It has long been hypothesised that skin sequestration contributes to efficient transmission. Although skin sequestration would have major implications for our understanding of transmission biology and the suitability of mosquito feeding methodologies to measure the human infectious reservoir, it has never been formally tested. In two populations of naturally infected gametocyte carriers from Burkina Faso, we assessed transmission potential to mosquitoes and directly quantified male and female gametocytes and asexual parasites in: i) finger prick blood, ii) venous blood, iii) skin biopsies, and in pools of mosquitoes that fed iv) on venous blood or, v) directly on the skin. Whilst more mosquitoes became infected when feeding directly on the skin compared to venous blood, concentrations of gametocytes in the subdermal skin vasculature were identical to that in other blood compartments. Asexual parasite densities, gametocyte densities and sex ratios were identical in the mosquito blood meals taken directly from the skin of parasite carriers and their venous blood.We also observed sparse gametocytes in skin biopsies from legs and arms of gametocyte carriers by microscopy. Taken together, we provide conclusive evidence for the absence of significant skin sequestration of P. falciparum gametocytes. Gametocyte densities in peripheral blood are thus informative for predicting onward transmission potential to mosquitoes. Quantifying this human malaria transmission potential is of pivotal importance for the deployment and monitoring of malaria elimination initiatives.IMPORTANCEOur observations settle a long-standing question in the malaria field and close a major knowledge gap in the parasite cycle. By deploying mosquito feeding experiments and stage-specific molecular and immunofluorescence parasite detection methodologies in two populations of naturally infected parasite carriers, we conclusively reject the hypothesis of gametocyte skin sequestration. Our findings provide novel insights in parasite stage composition in human blood compartments, mosquito bloodmeals and their implications for transmission potential. We demonstrate that gametocyte levels in venous or finger prick blood can be used to predict onward transmission potential to mosquitoes. Our findings thus pave the way for methodologies to quantify the human infectious reservoir based on conventional blood sampling approaches to support the deployment and monitoring of malaria elimination efforts for maximum public health impact.

Aims: The aim of this study is to assess the prevalence of hemoglobin abnormalities and G6PD deficiency and their respective influence on anemia occurring in less than five years old children with clinical P. falciparum malaria living in Burkina Faso. Study Design: The study was a cross-sectional survey with descriptive focus conducted from December 2010 to January 2013 in Saponé health district and from May to October 2011 in Banfora health district. Clinical and laboratory data were collected. Blood smears on slides for malaria diagnosis by microscopy, hemoglobin level and filter paper for the detection of human genetic factors were performed. Methodology: A total of 386 subjects from Saponé (131) and Banfora (255) were enrolled. DNA collected from each sample was extracted using chelex-100 method and the human genetic resistance factors background was assessed by RFLP-PCR.  Abnormal hemoglobin patients were classified as NonAA while AA was defined the normal hemoglobin. Results: In this study, 70.98% (274/386) were classified normal hemoglobin (AA) while 29.02% (112/386) of subjects were carrying at least one abnormal (NonAA) allele: 24.35%AC, 3.63% AS, 0.78%CC and 0.26%SC. G6PD deficiency was 9.59% (37/386) among which, 4.92% for male and 4.66% in female. However, this gender difference was not statistically significant (p=1.00). 319/367 (86.92%) of the patients were anemic (59.4% with moderate anemia and 20.98% with mild anemia). The prevalence of anemia in G6PD deficient subjects was 83.33% (of which 58.33% were moderate anemia and 22.22% mild anemia). The difference between types of hemoglobin (p=0.64) in the occurrence of anemia (AA 87.64% and Non AA 85.18%) was not statistically significant. Conclusion: This study showed that the prevalence of these genetic factors was relatively low among children with clinical falciparum malaria with high parasite density. In addition, these factors appear to have no effect on anemia.

Introduction: In spite of considerable progress, malaria remains a public health problem in many areas, particularly in sub-Saharan Africa. One major complexity of malaria disease is caused by the development and the spread of vector and parasite resistance to insecticides and antimalarial drugs respectively. The Pfcrt76T gene mutation has been validated as a marker conferring resistance to chloroquine and other antimalarial drugs. The extension of Plasmodium falciparum resistance to commonly used antimalarial drugs (chloroquine, sulfadoxine-pyrimethamine) led to the adoption and the use of artemisinin-based combinations in Burkina Faso since 2005. Aims: The present study was initiated to assess the prevalence of the Pfcrt76T mutation in two different malaria epidemiological setting after a decade of introduction of artemisinin-based combination therapies (ACTs) in Burkina Faso.  Methodology:  The study population consisted of 181 uncomplicated malaria patients recruited in Banfora and Saponé health districts in 2012 and 2013. Blood samples were collected from finger prick on filter paper, dried and sent to the Molecular Biology Laboratory at Centre National de Recherche et de Formation sur le Paludisme (CNRFP) for molecular analyzes. DNA of Plasmodium falciparum was extracted with DNA extraction kit (Qiagen®) and the Pfcrt76T mutation was determined based on Polymerase Chain Reaction / Restriction Fragment Length Polymorphism technique (RFLP). Results:  The results of this study showed that the frequency of the pfcrt76T mutant allele (33.7%) was statistically lower than the Pfcrt76K wild-type allele (57.4%) in the study area. Moreover, the prevalence of Pfcrt76T mutation was neither associated with the patient age nor with the parasite density while a significant difference was observed between the two epidemiological setting, Banfora and Saponé. Conclusion: The findings of this study has shown a drop in the prevalence of mutant parasites Pfcrt76T in both the study area eight years after the introduction of ACTs compared to previous studies.

Aims: The aim of this study was to assess the impact of hemoglobin polymorphisms and G6PD deficiency on the course of uncomplicated malaria infection in children aged from 2 to 10 years in Burkina Faso. Study Design: The study was conducted as a longitudinal study in Banfora health district. A total of 150 children aged from 2 to 10 years was enrolled and followed up between May 2015 and February 2016. Blood samples were collected at four different time points: before infection (Visit 1), during asymptomatic parasitemia (Visit 2), during symptomatic parasitemia (Visit 3) and three weeks after treatment (Visit 4). Clinical examination, hematology parameters and malaria diagnosis using microscopy were performed. Hemoglobin and G6PD typing were done using PCR-RFLP. Hemoglobin AA genotypes were defined as normal hemoglobin while Hemoglobin AC, AS and SS were defined as abnormal hemoglobin (hb non-AA). Results: The prevalence of hemoglobin (hb) genotypes was 81.21% for AA while hb non-AA genotypes were estimated at 18.79% (12.08% for hbAC, 6.04% for hbAS and 0.67% for HbSC). The prevalence of G6PD genotypes was 89.26% and 10.74% for normal G6PDn and G6PD deficiency respectively. The prevalence of asymptomatic carriers of P. falciparum was not affected neither by the genotypes of Hemoglobin, nor by the G6PD deficiency. Conversely, the risks of developing uncomplicated malaria in G6PD deficiency (G202A) group, was significantly lower (p = 0.04). The results showed a significant difference (p˂0.0001) in the means of P. falciparum parasite densities between asymptomatic and symptomatic phase in Hemoglobin AA genotypes carriers while the means of parasite density was comparable in non-Hemoglobin AA carriers.    Conclusion: Our study showed that G6PD deficiency protects against clinical malaria while P. falciparum parasite density increasing was correlated with carrying hemoglobin genotypes AA.

Human genetic factors mechanisms are known to protect against malaria. However, the mechanism underlying the influence of human genetic variation on Plasmodium falciparum (P.falciparum) genetic diversity is still a research purpose. The aim of this study is to assess the effect of haemoglobin variants and Glucose-6-Phosphate-Dehydrogenase (G6PD) variation on the P. falciparum merozoite surface protein (msp1, msp2), and the glutamate rich protein (glurp) genetic diversity in children living in Burkina Faso (BF). A cross-sectional study was carried out at Banfora and Saponé health districts and 386 children less than five years were enrolled. DNA collected from each sample was extracted using chelex-100 method and then analyzed by a nested PCR of msp1, msp2 and glurp genes while the human genetic resistance factors background was assessed by RFLP-PCR. A total of 112 (29.02%) subjects were classified as abnormal haemoglobin and 37 (9.59%.) were identified as G6PD deficiency The distribution of the msp1 and msp2 allelic families was not different according to haemoglobin type (p=0.70 and 0.90 respectively) and G6PD type (p=0.89 and 0.82 respectively). The prevalence of the glurp gene was 93.00% and there was no statistical difference in its distribution according to the human factors (p=0.24 and p=0.95 for haemoglobin and G6PD types respectively). The analysis of the mean multiplicity of P. falciparum infection (MOI) based on haemoglobin variants showed msp1 with high values 2.96 and 3.12 for Normal haemoglobin and Abnormal haemoglobin respectively. However, according to the G6PD type, there were no differences of MOIs between normal G6PD and deficient G6PD carriers. The study showed the P. falciparum genetic diversity was not affected by human genetic factors based on the analysis of msp1, msp2 and glurp.

Aim: The present study aimed to evaluate the Plasmodium falciparum genetic diversity according to the host hemoglobin and G6PD genetic variants during the course of malaria in infected children aged from 2 to 10 years and living in endemic area in Burkina Faso. Study Design: The study was designed as a longitudinal follow up conducted between May 2015 and February 2016 in Banfora health district, Burkina Faso. Methodology: We included 136 subjects (73 males and 63 females; age range from 2-10 years). Blood thick and thin film was done by capillary blood. Venous blood was collected for DNA extraction. Malaria diagnosis was done by microscopy. Human and parasite DNA were extracted based on Qiagen kit procedure. Then, hemoglobin and G6PD were genotyped by RLFP-PCR while the msp1, msp2 and eba175 genes were typed by a nested PCR. All PCR products were analyzed by electrophoresis on a 1.5-2% agarose gel and alleles categorized according to the molecular weight. Results: The prevalence of hemoglobin type was 19.11% for abnormal hemoglobin and 80.9% for normal hemoglobin carriage. The prevalence of G6PD type was 91.18% for normal and 8.82% for G6PD deficiency carriage, respectively. The prevalence of msp1 allelic families was 81.60%, 80.80% and 67.20% for k1, ro33 and mad20 respectively while for msp2 gene, fc27 and 3D7 allelic family the prevalence was 70.53% and 69.64% respectively. The eba175 allelic families’ distribution showed 77.31% and 40.21% for fcr3 and Camp respectively. There was no difference in multiplicity of infection (MOI) according to hemoglobin genotypes and G6PD types. We found that k1 was the predominant allelic family of msp1 in normal hemoglobin genotype (AA) and normal G6PD type. The mixed infection of eba175 was statistically higher in abnormal hemoglobin (p=0.04). There was no statistical difference between fcr3 and camp prevalence excepted in G6PD deficient type. The polymorphism results showed that the prevalence of 450 bp in fc27 was statistically significantly higher in normal hemoglobin variant carriers (AA) than abnormal hemoglobin carriers (p=2.10 -4)). However, the prevalence of 350 bp in fc27 was statistically higher in normal G6PD than deficient G6PD carriers (p=0.034). Conclusion: Our result showed that the distribution of msp1 and eba75 polymorphism could be influenced by hemoglobin and G6PD variants. These results suggest that hemoglobin and G6PD could influence P. falciparum genetic diversity.