Laboratory Propagation of Anopheles funestus Using Novel Breeding Techniques in Western Kenya

Abstract

Background: Malaria remains a formidable public health challenge in Sub-Saharan Africa, with Anopheles funestus sensu stricto (s.s.) recognised as a key vector driving residual transmission. Despite its reputation, research on this species is hindered by the complexities associated with its laboratory colonisation. This study designed and evaluated a new breeding technique for wild Anopheles funestus s.s. and assessed the vectorial competence of laboratory-reared populations.
Methods: Gravid female Anopheles mosquitoes were collected from indoor and outdoor sites in Western Kenya. An in-cup forced oviposition method was employed to secure eggs, which were reared in four water types: Lake water, rainwater, purified water, and pre-conditioned An. gambiae water. The resultant adults were subjected to membrane feeding assays using Plasmodium falciparum infected blood.
Results: The modified in-cup forced oviposition technique yielded an average fecundity of 114.9 eggs per female vector. Raw Lake Victoria water proved to be the most optimal rearing environment, supporting the highest adult emergence rate and the shortest developmental cycle. Conversely, larval development was significantly delayed in water pre-conditioned by Anopheles gambiae. Subsequent artificial membrane feeding assays involving 2,076 mosquitoes across eight transmission cycles resulted in zero Anopheles funestus s.s. individuals testing positive for Plasmodium falciparum sporozoites. However, a small proportion of Anopheles arabiensis vectors were infected, demonstrating a mean parasite infection rate of 6.74% with a mean sporozoite load of 1.25 pg/μl via Enzyme-Linked Immunosorbent Assay (ELISA), and a mean infection rate of 22.9% with a mean load of 1.42 copies/cell via real-time quantitative Polymerase Chain Reaction (PCR) diagnosis.
Conclusions: This study demonstrated that in-cup forced oviposition and raw Lake Victoria water can be vital in establishing large An. funestus s.s populations for experimental studies. The findings are crucial for understanding the biology of the parasite, testing potential vaccines and drugs and developing effective control measures.