Potential interaction between clorsulon and ivermectin for malaria vector control.

Area of Science:

• Veterinary Medicine
• Parasitology
• Medical Entomology

Background:

• Mass ivermectin treatment of livestock (MITL) is explored for malaria control due to ivermectin's (IVM) mosquito-lethal effects.
• Current veterinary practices increasingly use IVM co-formulated with clorsulon (CLO) to treat livestock helminth and liver fluke infections.
• Control of Fasciola hepatica in livestock offers One Health benefits by reducing human exposure to liver flukes.

Purpose of the Study:

• To evaluate the direct effect of clorsulon (CLO) on Anopheles dirus mosquito survival.
• To determine if CLO alters the mosquito-lethal efficacy of ivermectin (IVM) when co-administered.
• To assess the implications of IVM-CLO co-formulations for malaria vector control via MITL.

Main Methods:

• Anopheles dirus mosquitoes were exposed to varying concentrations of CLO (1-10,000 nM) via blood feeding, with survival monitored for 10 days.
• Co-feeding experiments involved An. dirus blood-fed on IVM (4 and 6 ng/mL) with or without CLO at concentrations simulating cattle peak (Cmax) and five times Cmax.
• Mosquito survival was assessed for 10 days post-feeding in all experimental groups.

Main Results:

• CLO alone exhibited no lethal effect on Anopheles dirus mosquitoes at tested concentrations.
• Co-feeding IVM with CLO did not alter the mosquito-lethal effect of IVM.
• The efficacy of IVM in MITL for mosquito control is unlikely to be affected by the presence of CLO in co-formulations.

Conclusions:

• Clorsulon does not possess direct mosquito-lethal properties and does not interfere with ivermectin's efficacy against mosquitoes.
• Current IVM-CLO co-formulations used in livestock are compatible with the use of MITL for malaria vector control.
• MITL with IVM-CLO offers a dual benefit of livestock parasite control and potential malaria transmission reduction, aligning with One Health principles.