Assessment of the relationship between gametocyte density, multiplicity of infection and mosquito infectivity in Plasmodium falciparum infections

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Abstract Background: Malaria is a major public health threat in sub-Saharan Africa. Asymptomatic P. 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 (age 5-15 years) in Mbita, western Kenya and further analyse the association between gametocyte density, multiplicity of infection (MOI) and mosquito infectivity. Methods: Rapid diagnostic test (RDT) was used to screen for P. falciparum parasite infection among asymptomatic schoolchildren (5-15 years old) residing in Mbita, Western Kenya and the results were further verified using microscopy. Participants positive for P. falciparum infection were further screened for gametocyte carriage and those positive were used to feed laboratory reared An. gambiae s.s. mosquitoes using membrane feeding method. Genomic DNA was extracted from dry blood spots (DBS) samples and P. falciparum populations were genotyped using 10 polymorphic microsatellite markers. Assessment of the association between MOI and gametocyte density and mosquito infection rates was conducted. Results: The prevalence of Plasmodium falciparum infection among the study population was 29.1%. A significantly higher P. falciparum infection was found among the male gender (n=764, p -value < 0.05) compared to the females (n=657). Gametocyte prevalence among the study population was 2%. Children (5-9 years) have a higher risk of gametocyte carriage (Odd Ratios = 2.1 [95% CI = 1.3–3.4], P = 0.002). Our results indicate a significant and positive combined effect of gametocyte density and MOI on mosquito infection rate (R = 0.825, p < 0.0001). Conclusion: The study reports a relatively stable year-round gametocyte carriage among the study population. This pattern of gametocyte carriage signals the role of schoolchildren in maintaining malaria transmission in the study area. A strong positive correlation was found between gametocyte density, multiplicity of infection and mosquito infectivity.

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