Efficacy of fenbendazole against tapeworms in calves.

Forty-five commercial-grade Angus calves naturally infected with tapeworms (Moniezia sp) were used in 2 controlled experiments to evaluate the cestocidal efficacy of 3 dosage levels of fenbendazole, methyl-5-(phenylthio) -2-benzimidazolecarbamate. In the 1st trial, 15 calves were divided into 3 groups of 5 each. One group served as nonmedicated controls. Other groups were drenched with fenbendazole at dosage rates of 10 and 15 mg/kg of body weight. Thirty calves used in the 2nd experiment were divided into 3 equal groups. One group served as nonmedicated controls and the other 2 groups were drenched at dosage rates of 7.5 and 10 mg/kg. Calves were necropsied 13 days after treatment. Doses of 10 and 15 mg/kg were 100% efficacious in reducing the number of tapeworm scolices, and a dose of 7.5 mg/kg was 91.7% effective. Signs of toxicosis were not observed in medicated cattle from time of treatment to necropsy.