Efficacy of ivermectin oral liquid for horses.

This research investigates the effectiveness of a new liquid formulation of ivermectin—a popular equine anthelmintic suitable for treating various kinds of parasites—when administered orally to horses, comparing its efficacy with ivermectin paste. The study was conducted on 100 horses found in two farms and lasted for approximately four months.

Introduction and Background

• The oral liquid formulation of ivermectin, an anti-parasitic drug commonly used in horses, has garnered significant interest. The anthelmintic—used to destroy parasitic worms—is known for its extensive efficacy, broad spectrum of action, and large margin of safety.
• The medication is effective against various parasites in all their life stages, including Gasterophilus spp., benzimidazole-resistant small strongyles, Dictyocaulus spp., and microfilariae of Onchocerca cervicalis.
• Despite noted efficacy against adult Parascaris equorum of 95-100%, questions have been raised about its potency against immature stages of this parasite. Ivermectin has shown increased effectiveness against immature Parascaris larvae when given orally, compared to injection.
• Ivermectin is extremely proficient at combating adult egg-producing nematode parasites, causing fecal ova counts to drop significantly within 7-14 days post-treatment. This reduction remains steady for at least 63 days. However, counts generally show a slow increase between 13 to 26 weeks post-treatment.

Research Method

• The experiment was conducted on two Albertan farms beginning in February 1986, covering a total population of 100 horses of various ages.
• The novelty of this research was the new liquid formulation of the drug. It was designed to be administered via oral drench or nasogastric intubation at a dose of 1mL/50 kg (200 ug/kg of body weight). Its efficacy was compared against the traditional ivermectin paste.
• The horses were divided into four randomly assigned groups: no medication, ivermectin oral liquid via nasogastric intubation, oral liquid via drench (administered with a hypodermic syringe), and ivermectin paste. Horses that were medicated were closely monitored for first 5 min, at each hour for 4 h, and once daily for 14 d after treatment.

Results

• Ivermectin—whether administered as liquid by oral drench, nasogastric intubation, or as a paste—displayed substantial effectiveness.
• Fecal samples were collected from all horses pre and post-treatment, and a third sample was collected from 55 horses from one farm after approximately 16 weeks. The samples were examined using specific techniques to calculate the egg count.
• The findings reaffirm the efficacy of Ivermectin and sheds light on the acceptability and efficacy of the new oral liquid formulation.