Biting behaviour and the spatio-temporal dynamics of malaria vectors in different ecological zones in Ghana

Abstract

Background: Significant decrease in malaria morbidity and mortality have been attained using long-lasting insecticide treated nets and indoor residual spraying. Selective pressure from these control methods influences change in vector bionomics and behavioural pattern. There is a need to understand how insecticide resistance drives behavioural changes within vector species. This study aimed to determine the spatio-temporal dynamics and biting behaviour of malaria vectors in different ecological zones in Ghana in an era of high insecticide use for public health vector control.Methods: Adult mosquitoes were collected during the dry and the rainy seasons in 2017 and 2018 from five study sites in Ghana in different ecological zones. Indoor and outdoor biting mosquitoes were collected per hour from 18:00 to 06:00 hours employing the human landing catches (HLC) technique. Morphological and molecular species identification of vectors were done using identification keys and PCR respectively. Genotyping of insecticide resistant markers was done using the TaqMan SNP genotyping probe-based assays. Detection of P. falciparum sporozoites was determined using PCR.Results: A total of 50,322 mosquitoes belonging to four different genera were collected from all the study sites during the sampling seasons in 2017 and 2018. Among the Anophelines were Anopheles gambiae s.l. 93.16%, (31055/33,334), An. funestus 2.07%, (690/33,334), An. pharoensis 4.63%, (1545/33,334), and An. rufipes 0.13% (44/33,334). Overall, 76.40%, (25,468/33,334) of Anopheles were collected in the rainy season and 23.60%, (7,866/33,334) in the dry season. There was a significant difference (z = 2.410; p = 0.0160) between indoor biting (51.09%; 15,866/31,055) and outdoor biting An. gambiae s.l. (48.91%; 15,189/31,055). The frequency of the Vgsc-1014F mutation was slightly higher in indoor biting mosquitoes (54.90%) than outdoors (45.10%). Overall, forty-four pools (44) of samples were positive for P. falciparum CSP giving an overall sporozoite rate of 0.07%.Conclusion: Anopheles gambiae s.l. were more abundant indoors across all ecological zones of Ghana. The frequency of G119S was higher in indoor than outdoor from all the study sites, but higher sporozoite rates in outdoor mosquitoes in Dodowa and Kpalsogu. There is thus, an urgent need for a supplementary malaria control intervention to control outdoor biting mosquitoes.