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.

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.