Efficacy of moxidectin equine oral gel against endoscopically-confirmed Gasterophilus nasalis and Gasterophilus intestinalis (Diptera: Oestridae) infections in horses.

The research study focused on the efficacy of moxidectin, an oral gel for horses, against two types of equine bot larvae: Gasterophilus nasalis, found in the upper part of the small intestine, and Gasterophilus intestinalis, in the stomach. The study revealed that the gel was highly effective, alleviating up to 97.6% of infections caused by these parasites.

Setting and Participants

• This research involved screening 47 horses thought to be naturally infected with equine bot larvae.
• A 3 metre video gastroscope was used to identify and confirm the presence of the larvae in the horses’ digestive tract.
• From this initial pool, 14 horses which had dual infections were selected and divided into two treatment groups.

Treatment Method

• Group 1 consisted of seven horses that received a single treatment of 2% moxidectin oral gel, applied at a dose proportional to the horse’s body weight.
• Group 2, the control group, was made up of seven horses that received no treatment.

Outcome Evaluation

• 14 days after the treatment, all the horses were subjected to necropsy (postmortem examination) and bot larvae were extracted from their stomach and proximal duodenum.
• The larvae were then identified as per their species and stage of growth, and their numbers were counted.

Results

• As per the findings of the study, the moxidectin gel demonstrated a high level of efficacy against both types of larvae.
• The gel demonstrated 100% effectiveness against third-instar G. nasalis larvae, and 97.6% effectiveness against G. intestinalis.
• The trial thus demonstrated the effectiveness of moxidectin gel as a boticide.

Additional Observations

• Apart from establishing the effectiveness of the gel, the study indicated that the method of gastroscopy/duodenoscopy is a viable one for confirming bot larvae infection in the horse’s digestive tract.