Abstract:
Malaria is considered the main cause of morbidity and mortality in most countries of the sub- Saharan Africa. Though elimination of the disease is a priority in some African countries such as Botswana, there are bottlenecks that make it difficult to achieve such target. Factors associated with the environment and mosquito-vector capacity for disease transmission have contributions towards challenges affecting disease elimination. These are dynamics which have not been explored in the country involving the presence of water bodies, efficacy of the insecticides currently registered and used for vector control and the prevailing climate change on vector performance. First, it was showed that water bodies indeed generally attract mosquito densities with high significant (p< 0.001) reduction of mosquitoes with distance away from water bodies. Mosquitoes were trapped with Center for Disease Control (CDC) miniature light traps with distance (embankment, 50m, 100m and 3.5km) from the water bodies (rivers). Secondly, the efficacy of registered and currently used insecticides on Anopheles arabiensis (as per World Health Organization standards) was investigated. Results showed pyrethroids were less efficacious though generally fast in action. Prominent pyrethroid resistance was observed in Okavango than Ngamiland and Bobirwa malaria endemic districts, indicating differential pesticide resistance in space. Finally, the thermal tolerance to activity of An. arabiensis adults (female and male) and the larvae were assessed. Results showed females had a wider range of critical thermal limits (CTLs) as compared to males with implications on possible future malaria transmission in climate change scenarios. Overall, Okavango showed the highest densities of mosquitoes with prominent pyrethroid resistance. Furthermore, mosquitoes from the district showed a wider range of CTLs than other districts. Therefore, a recommendation is made on indoor residual spraying to consider rotational use of insecticides which may reduce selection pressure on mosquitoes as a strategy of managing resistance on mosquito vector that rest indoors. This work recommends alternative control methods to the endemic districts as mitigating strategies towards resistance management. The country may utilize the current novel molecular and biotechnological approaches, biological methods and alternatives of botanical ‗soft‘ pesticides which are environmental friendly in the control of vector mosquitoes.
