Compatibility Interactions between Anopheles gambiae and Plasmodium falciparum in a Malaria Endemic Region in Kisumu, Kenya 

Abstract

<title>Abstract</title> Insecticide resistance and outdoor transmission have reduced the effectiveness of existing malaria transmission prevention strategies. As a result, targeted approaches to support continuing malaria therapies, 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. <italic>Plasmodium falciparum</italic> gametocyte carriers were identified by Microscopy. Subsequently, carries were used to feed colony bred <italic>Anopheles gambiae</italic> 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 <italic>P. falciparum</italic>. Of all confirmed <italic>P. falciparum</italic> 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 (S98T0); 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 infectious Pfs47 haplotypes observed from genetically heterogeneous parasite populations in endemic regions illuminates vector compatibility to refracting <italic>P. falciparum</italic> using the hypothesized lock and key analogy. This acts as a bottleneck that increases the frequency of <italic>P. falciparum</italic> haplotypes that escape elimination by vector immune responses. The interaction can be used as a potential target for transmission blocking through a refractory host.