Differential activity of cythioate against female and male Ctenocephalides felis on cats

Abstract

Summary A study was conducted to determine whether cythioate, a systemically active insecticide, has different activity against male and female Ctenocephalides felis, the cat flea. Eighteen cats were allotted equally to 1 control and 2 treatment groups and infested on day 0 with fixed ratios of male and female cat fleas. Cats in the untreated control group and treatment group 2 were infested with 50 fleas with a female-to-male ratio of approximately 2:1. Cats in treatment group 1 were infested with 50 fleas with a female-to-male ratio of 1:1. Cythioate was administered orally to cats in the treatment groups at the dosage of 3.6 mg/kg of body weight once daily on days 0 and 3. Fleas remaining after treatment were removed, sexed, and counted on day 5. The efficacy of cythioate after 2 dosings was 82.8 and 33.4% against female and male fleas, respectively. The greater activity against female fleas resulted in posttreatment female-to-male ratios in treatment groups 1 and 2 of 0.32:1 and 0.54:1, respectively. Fleas recovered from untreated control cats had a final female-to-male ratio of 2.27:1. Total population control efficacies for treatment groups 1 and 2 were 61.7 and 67.6%, respectively.