Anthelmintic efficacy of albendazole in calves with naturally acquired Fasciola hepatica infections.

The anthelmintic efficacy of albendazole was evaluated as an oral drench at dosages of 15.0, 10.0, and 7.5 mg/kg of body weight in 3 groups crossbred Brahman calves (n = 12 group) infected with Fasciola hepatica. Although posttreatment fluke ova counts for the 3 albendazole treatment groups were significantly (P less than 0.01) lower (av 82%) than were counts in nontreated calves, there were no significant differences in the responses to the different albendazole treatments. At necropsy, adult fluke counts in treated calves were lower (P less than 0.05) than were counts in nontreated calves, but as with ova counts, a dose-related trend was not noticed. Efficacy against adult flukes was 63.4%, 50.0%, and 56.6% for 15.0, 10.0, and 7.5 mg/kg, respectively. Activity against immature flukes was not observed in calves given the 10.0 and 7.5 mg/kg, but there was a 36% decrease of flukes in those calves given 15.0 mg/kg. Significant decreases (P less than 0.05) in fluke ova viability were observed for the 3 treatment groups in which 12.9% of ova collected at necropsy failed to embryonate (control group av 6.7%). Posttreatment weight changes were not significantly different, although gains were greater within albendazole treatment groups. Decreases in gastrointestinal parasite ova counts after treatment were 98%, 93%, and 93% for groups given 15.0, 10.0, and 7.5 mg/kg, respectively. Ova counts in nontreated calves increased 26.2% during the same period.