Effectiveness of an ivermectin liquid formulation given by nasogastric tube against strongyles in horses.

Twenty horses were treated with ivermectin either by nasogastric tube with a liquid formulation for sheep or per os with a paste formulation for horses at a dosage of 200 mug/kg of body weight. Fecal samples were collected from these horses and from ten untreated horses at the time of treatment and every 2 wk thereafter for up to 10 wk. The samples were examined for nematode eggs using the Cornell-McMaster dilution and the Cornell-Wisconsin Double Centrifugation procedures.There were no signs of toxicosis in horses treated with ivermectin. Strongyle eggs were found in the feces of all horses before treatment. Subsequently, they were found in untreated horses, but not in treated horses at 2 wk nor in most of them for up to 8 wk after treatment. At 10 wk most of these horses had strongyle eggs in their feces, but in general fewer than at pretreatment.