Effectiveness of ivermectin in the treatment of equine Parascaris equorum and Oxyuris equi infections.

Fifteen horses harboring naturally acquired, patent Parascaris equorum and Oxyuris equi infections were equally allotted to 3 treatment groups given (1) injectable vehicle; (2) injectable ivermectin at the dose rate of 200 microgram/kg of body weight; and (3) injectable ivermectin at the rate of 300 microgram/kg. All treatments were given IM in the neck. All animals were killed 14 days after treatment and examined for the targeted nematodes. Regardless of dose rate, ivermectin proved 100% effective in the removal of adult O equi and P equorum infections. Levels of immature P equorum were decreased by 98.5% in both ivermectin-treated groups. Oxyuris equi 4th-stage larval injections were decreased by 95.7% and 99.9% by the 200 and 300 microgram/kg ivermectin treatments, respectively. Adverse reactions to the injections of drug were not seen.