Common predators and factors influencing their abundance in Anopheles funestus aquatic habitats in rural south-eastern Tanzania

Abstract

BackgroundThe role that larval predators play in regulating the population of malaria vectors remains relatively unknown. This study aimed to investigate the common predators that co-exist with Anopheles funestus group larvae and evaluate factors that influence their abundance in rural south-eastern Tanzania. MethodsMosquito larvae and predators were sampled concurrently using standard dipper (350 ml) or 10 L bucket in nine villages in southern Tanzania. Predators were identified using standard identification keys. All positive habitats were geo-located and their physical features characterized. Water physicochemical parameters such as dissolved oxygen (DO), pH, electrical conductivity (EC), total dissolved solids (TDS) and temperature were also recorded. ResultsA total of 85 previously identified An. funestus aquatic habitats were sampled for larvae and potential predators. A total of 8,295 predators were sampled. Of these Coenagrionidae 57.7% (n=4785), Corixidae 12.8% (n=1,060), Notonectidae 9.9% (n=822), Aeshnidae 4.9% (n=405), Amphibian 4.5% (n=370), Dytiscidae 3.8% (n=313) were common. A total of 5,260 mosquito larvae were sampled, whereby Anopheles funestus group were 60.3% (n= 3,170), Culex spp. 24.3% (n= 1,279), An. gambie s.l. 8.3% (n= 438) and other anophelines 7.1% (n= 373). Permanent and aquatic habitats larger than 100m2 were positively associated with An. funestus group larvae (P<0.05) and predator abundance (P<0.05). Habitats with submerged vegetation were negative associated with An. funestus group larvae (P<0.05). Only dissolved oxygen (DO) was positively and significantly affect the abundance of An. funestus group larvae (P<0.05). While predators abundance were not impacted by all physicochemical parameters. ConclusionSix potential predator families were common in aquatic habitats of An. funestus larvae group. Additional studies are needed to demonstrate the efficacy of different predators on larval density and adult fitness traits. Interventions leveraging the interaction between mosquitoes and predators can be established to disrupt the transmission potential and survival of the An. funestus mosquitoes.