Resting behaviour of malaria vectors in highland and lowland sites of western Kenya: Implication on malaria vector control measures

Abstract

Background Understanding the interactions between increased insecticide resistance and resting behaviour patterns of malaria mosquitoes is important for planning of adequate vector control. This study was designed to investigate the resting behavior, host preference and rates of Plasmodium falciparum infection in relation to insecticide resistance of malaria vectors in different ecologies of western Kenya. Methods Anopheles mosquito collections were carried out during the dry and rainy seasons in Kisian (lowland site) and Bungoma (highland site), both in western Kenya using pyrethrum spray catches (PSC), mechanical aspiration (Prokopack) for indoor collections, clay pots, pit shelter and Prokopack for outdoor collections. WHO tube bioassay was used to determine levels of phenotypic resistance of indoor and outdoor collected mosquitoes to deltamethrin. PCRbased molecular diagnostics were used for mosquito speciation, genotype for knockdown resistance mutations (1014S and 1014F) and to determine specific host blood meal origins. Enzyme-linked Immunosorbent Assay (ELISA) was used to determine mosquito sporozoite infections. Results Anopheles gambiae s.l. was the most predominant species (75%, n = 2706) followed by An. funestus s.l. (25%, n = 860). An. gambiae s.s hereafter (An. gambiae) accounted for 91% (95% CI: 89-93) and An. arabiensis 8% (95% CI: 6-9) in Bungoma, while in Kisian, An. arabiensis composition was 60% (95% CI: 55-66) and An. gambiae 39% (95% CI: 34-44). The

Extensive new Anopheles cryptic species involved in human malaria transmission in western Kenya

“…arabiensis was a dominant vector species in the lowlands of Homa Bay than highlands of western Kenya. This species is a common vector of malaria in the lowlands of East Africa 38,39 . A low human blood index and low sporozoite rate of An.…”

Plasmodium falciparumincreases its investment in gametocytes in the wet season in asymptomatic individuals

“…Chulaimbo, An. Arabiensis forms the predominant mosquito vector species followed by Anopheles gambiae s.s. (Machani et al, 2020), whereas in Homa Bay An. funestus is the predominant mosquito vector species (McCann et al, 2014).…”

“…None of the study participants had been treated with antimalarial drugs within the three days prior blood sampling. is the second predominant mosquito vector (Machani et al, 2020). In Homa Bay, An.…”

“…Malaria control requires mapping potential silent gametocyte reservoirs in time and space. In many settings with pronounced seasonality in rainfall, Anopheles mosquitoes are few in the dry season as opposed to wet season where they are plentiful, resulting in transmission primarily occurring during and shortly after the wet season (Machani et al, 2020;Huestis & Lehmann, 2014;Jawara et al, 2008;Ouédraogo et al, 2008;Hamad et al, 2002). It is not known how far Plasmodium falciparum adapts its transmission potential to changes in vector abundance across seasons.…”

“…Areas of western Kenya experience perennial malaria transmission with peaks in vector density and transmission coinciding with seasonal rains in April-August and October-November (Machani et al, 2020;Desai et al, 2014). In regions with pronounced seasonality in vector abundance, parasites could increase their fitness by increasing their gametocyte conversion rate in the wet season.…”