Impact of ivermectin-blood meals from treated cattle on mortality and reproductive parameters of <i>Aedes aegypti</i> (Diptera: Culicidae) for vector control

Growing of insecticide resistance in Aedes aegypti underscores the need for alternative vector control tools. Ivermectin, an endectocide with mosquitocidal properties, is currently evaluated against Anopheles for residual malaria control. Its potential use against Ae. aegypti within integrated strategies also warrants investigation. This study assessed the effects of ivermectin-treated cattle blood on the survival and reproductive parameters of two Ae. aegypti strains: Bora Bora (insecticide susceptible) and Bobo (insecticide resistant). Laboratory-reared females were fed on cattle treated with ivermectin at doses of 0.6, 0.8, and 1 mg/kg. Blood meals were offered at 0, 2, 7, 14, 21, and 28 days after injection (DAI). Daily mortality, oviposition probability, egg production, and egg hatching rates were recorded and compared to mosquitoes fed on untreated cattle. For the Bora Bora strain, all ivermectin doses significantly reduced mosquito survival and reproductive outputs. The 1 mg/kg dose reduced survival by 66% at 2 DAI and 30% at 14 DAI. Oviposition probability declined by up to 51.9%, and egg production by 42.9%. For the Bobo strain, survival was significantly affected by the 1 mg/kg dose only (-14% at 7 DPI), though all doses led to reduced hatching rates (up to -50.7%). These findings confirm that injectable ivermectin can impair Aedes aegypti survival and fertility, particularly in susceptible populations. However, it's reduced efficacy against resistant strains and short-time toxicity limits its effectiveness in field settings. Developing a formulation that can maintain mosquitocidal concentrations over extended periods will be essential to enhance impact, cost-effectiveness, and operational feasibility.