The efficacy of ivermectin against Strongyloides papillosus in cattle.

The efficacy of ivermectin was evaluated against Strongyloides papillosus in four controlled trials in cattle. Thirty-four animals were inoculated subcutaneously with S. papillosus 3rd stage larvae 14-24 days before treatment. At 7-14 days after treatment, calves were slaughtered and the number of adult S. papillosus present in the small intestine counted. Faecal egg counts were carried out before and after treatment. Seventeen control animals received a single subcutaneous injection of vehicle solution at a dose volume of 1 ml/50 kg body weight, and 17 calves were treated once with ivermectin at 200 mcg/kg b.w. using a 1% injectable solution (IVOMEC Injection Merck & Co., Inc.), subcutaneously. The control animals had a mean burden of 5,913 worms, while ivermectin significantly (p less than 0.01) reduced the number of adults S. papillosus by more than 99%. There was a greater than 99% reduction in the faecal egg count of treated animals at the last faecal examination compared with that pre-treatment.