Effects of Biological Control on Survival and Development of Immature Anopheles Mosquitoes

Abstract

Malaria, a global public health concern, is transmitted through the bite of infected mosquitoes, resulting in significant morbidity and mortality. The overuse of chemical insecticides for malaria vector control has led to the development of resistance and raised environmental and non-target species concerns. As a result, there is a renewed focus on establishing locally sustainable and cost-effective alternative methods for malaria vector control. Predation has emerged as a significant regulatory mechanism for malaria vectors, offering the potential to prevent female anopheles from completing their life stages. This approach holds promise for addressing the challenges associated with traditional insecticide-based control methods. The objective of this study was to assess the predation efficacy of specific predators in an experimental mesocosm, as well as to evaluate the impact of these predators on the development of mosquito larvae, pupae, and adult emergence. The larvae and predators were sourced from various water bodies within the Gilgel Gibe watershed in Southwest Ethiopia. Our semi-field study utilized mesocosms constructed from plastic containers to replicate the natural aquatic habitat of immature Anopheles mosquitoes. The predation efficacy of selected predators, including Belostomatidae, Notonectidae, and Corixidae, on Anopheles mosquito larvae was monitored through daily larval counts until they were consumed, perished, or reached the adult stage within the mesocosms. The study conducted from June to July 2021 involved the collection and rearing of adult mosquitoes that emerged from mesocosms in laboratory conditions. Female adults were monitored to assess the impact of predators on larval development, pupae development, and adult mosquito emergence. The predator to prey ratio in each replicate was maintained at 1:10, and the data collected was analyzed using R software with a risk of species 1 alpha set at 5% for all analyses. The findings revealed that Belostomatidae exhibited the highest efficiency as a predator of Anopheles mosquito larvae, followed by Notonectidae and Corixidae under semi-field conditions. It was observed that these predators exerted sub-lethal effects and indirect non-consumptive effects in addition to direct consumption. The presence of predators significantly affected both the number of adults that emerged and the developmental stage of those that survived predation.