211 - Re-purposing oral flea-and-tick products (=isoxazoline drugs) for mosquito control

Abstract: Systemic insecticides are drugs given to livestock, pets and people that kill blood-sucking arthropods that feed on medicated hosts. Ivermectin is a well-established systemic drug known to kill Anopheles mosquitoes and is currently being tested in the tropics for its potential to reduce malaria transmission. One problem with orally administered ivermectin is that one dose only kills mosquitoes for about a week. We evaluated the potential of a newer class of systemic drugs used in veterinary medicine for flea-and-tick control – i.e., isoxazoline drugs – to kill Anopheles mosquitoes. We compared residual efficacy against A. stephensi mosquitoes for ivermectin, fluralaner, sarolaner, and lotilaner when drugs were administered orally to white-footed mice. Mice were fed baits containing either ivermectin (5 mg/kg BW), fluralaner (50 mg/kg BW), sarolaner (4 mg/kg BW), lotilaner (40 mg/kg BW), or placebo (peanut butter only). Doses were 2x the recommended dose for each drug. At various times afterwards, mice were anesthetized and 20-30 mosquitoes fed on each mouse. Engorged mosquitoes were monitored for mortality. Using 50% mortality as our cut-off, we found that ivermectin lasted 6 days, fluralaner and sarolaner lasted 24 days, and lotilaner lasted 60 days. Lotilaner (trade name = Credelio^TM) appears to be a very useful systemic drug that can provide long-lasting mosquito control after a single oral dose.