Prevalence of asymptomatic P. falciparum gametocyte carriage in schoolchildren and assessment of the association between gametocyte density, multiplicity of infection and mosquito infection prevalence.

Background: Malaria is a major public health threat in sub-Saharan Africa. Asymptomatic Plasmodium falciparum gametocyte carriers are potential infectious reservoirs for sustaining transmission in many malaria endemic regions. The aim of the study was to assess the prevalence of gametocyte carriage and some of its associated risk factors among asymptomatic schoolchildren in Western Kenya and further analyse the association between gametocyte density, multiplicity of infection (MOI) and mosquito infection prevalence. Methods: Rapid diagnostic tests were used to screen for P. falciparum parasite infection among schoolchildren (5-15 years old) and the results were verified using microscopy. Microscopy positive gametocyte carriers were selected to feed laboratory reared An. gambiae s.l. mosquitoes using membrane feeding method. Genomic DNA was extracted from dry blood spot samples and P. falciparum populations were genotyped using 10 polymorphic microsatellite markers. Assessment of the association between MOI and gametocyte density and mosquito infection prevalence was conducted. Results: A significantly higher prevalence of P. falciparum infection was found in males 31.54% (764/2422) ( p-value < 0.001) compared to females 26.72% (657/2459). The microscopy gametocyte prevalence among the study population was 2% (84/4881). Children aged 5-9 years have a higher prevalence of gametocyte carriage (odds ratios = 2.1 [95% CI = 1.3-3.4], P = 0.002) as compared to children aged 10-15 years. After challenging An. gambiae s.l. by membrane feeding assay on gametocyte positive patient blood, our results indicate that 68.1% of the variation in mosquito infection prevalence is accounted for by gametocyte density and MOI (R-SQR. = 0.681, p < 0.001). Conclusions: Age was a significant risk factor for gametocyte carriage, as indicated by the higher risk of gametocyte carriage among the younger children (5-9 years). Gametocyte density and MOI statistically significantly predicted mosquito infection prevalence. Both of the variables added significantly to the prediction ( p < 0.05).