Abstract
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).
Highlights
The intensification of global and local malaria control measures has led to marked reduction in disease burden in many regions including sub-Saharan Africa
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 multiplicity of infection (MOI) (R-SQR. = 0.681, p < 0.001)
Demographic and parasitological characteristics of the study participants In this study, a total of 4881 schoolchildren were screened using rapid diagnostic tests (RDTs) and the parasite status confirmed by microscopy
Summary
The incidence of Plasmodium falciparum clinical cases and prevalence have declined by 40% and 50%, respectively, within the African continent between 2000 and 20151. Recent data indicates this trend might be reversing, with an estimated 213 million malaria cases and 380,700 related deaths in the World Health Organisation (WHO) African Region between 2017 and 2018, an increase relative to previous years. In Kenya, like many other African countries, P. falciparum is the dominant parasite species with about 70.2% of the population at risk of the disease. Asymptomatic Plasmodium falciparum gametocyte carriers are potential infectious reservoirs for sustaining transmission in many malaria endemic regions. 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. Assessment of the association between MOI and gametocyte density and mosquito infection prevalence was conducted.
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