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 infection prevalence.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. Microscopy positive gametocyte carriers were selected 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 29.11% (1421/4881). A significantly higher prevalence of P. falciparum infection was found among the male gender 31.54% (764/2422) (p-value < 0.001) compared to the females 26.72% (657/2459). The microscopy gametocyte prevalence among the study population was 2% (84/4881). Children (5-9 years) have a higher risk of gametocyte carriage (Odd Ratios = 2.1 [95% CI = 1.3–3.4], P = 0.002) as compared to those between the ages of 10-15 years. Our results indicate that, about 68.1% of the variation in mosquito infection prevalence is accounted for by the gametocytes density and MOI (R-SQR. = 0.681, p < 0.001).Conclusion: The study reports a P. falciparum infection prevalence of 29.11% with a gametocyte prevalence of 2% among the study population as determined by microscopy. 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). The gametocyte density and multiplicity of infection statistically significantly predicted mosquito infection prevalence. Both of the variables added significantly to the prediction, (p < 0.05).

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