Evaluation of Selected Insecticides and Drugs as Chemotherapeutic Agents against External Bloodsucking Parasites

Abstract

Body lice (Pediculus humanus corporis), mosquitoes (Aedes aegypti), ear mites (Psoroptes equi var. cuniculi) and the lone star tick (Amblyomma americanum) were permitted to take blood meals on rabbits dosed with various selected insecticides and drugs. Of 33 chemicals tested against lice, employing in most cases 300 mg./kg., several caused some mortality of lice. Several indandione derivatives caused complete kill. In further tests 2-rpivalyl-1,3-indandione, administered orally, subcut., intraven., or intramusc., caused nearly 100% kill of lice when given to rabbits at a dosage as low as 2.5 mg./kg. When incorporated into feed at the rate of 5 and 10 ppm., which provided daily doses of 0.1 and 0.25 mg./kg., respectively, the blood of the host became toxic to lice after about a week, without causing visible adverse effects on the host. Gamma benzene hexachloride was the only chemical among 31 tested which caused complete mortality of mosquitoes and the minimum effective dosage was between 5 and 25 mg./kg. At 100 to 300 mg./kg. it also killed ear mites, but failed to kill larvae and nymphs of the tick at 25 mg./kg. 2-Pivalyl-l,3-indan-dione killed larvae and nymphs of ticks at 25 mg./kg. but failed to do so at 5 mg./kg.