Plasmodium Falciparum Pfs47 Haplotype Compatibility To Anopheles Gambiae In Kisumu, A Malaria-Endemic Region Of Kenya.

Abstract

Insecticide resistance and outdoor transmission have reduced the effectiveness of existing malaria transmission prevention strategies. As a result, targeted approaches to support continuing malaria control, such as transmission-blocking vaccines, are required. Cross-sectional mass blood screening in children between 5 and 15 years was conducted in Chulaimbo, Kisumu, during the dry and wet seasons in 2018 and 2019. Plasmodium falciparum gametocyte carriers were identified by Microscopy. Subsequently, carriers were used to feed colony bred Anopheles gambiae females in serum replacement and whole blood membrane feeding experiments. The infection prevalence was 19.7% (95% Cl 0.003–0.007) with 95% of the infections being caused by P. falciparum. Of all confirmed P. falciparum infections, 16.9% were gametocytes. Thirty-seven paired experiments showed infection rates of 0.9% and 0.5% in the serum replacement and whole blood experiments, respectively, with no significant difference (P=0.738). Six Pfs47 haplotypes were identified from 24 sequenced infectious blood samples: Hap_1 (E27D and L240I), Hap_2 (S98T); Hap_3 (E27D); Hap_4 (L240I); Hap_5 (E188D); and Hap_6 without mutations. Haplotype 4 had the highest frequency of 29.2% followed by Hap_3 and Hap_6 at 20.8% each then Hap_1 with a frequency of 16.7%, whereas Hap_5 and Hap_2 had frequencies of 8.3% and 4.2% respectively. Varying frequencies of Pfs47 haplotypes observed from genetically heterogeneous parasite populations in endemic regions illuminates vector compatibility to refracting P. falciparum using the hypothesized lock and key analogy. This acts as a bottleneck that increases the frequency of P. falciparum haplotypes that escape elimination by vector immune responses. The interaction can be used as a potential target for transmission blocking through a refractory host.