Critical and controlled tests of activity of moxidectin (CL 301,423) against natural infections of internal parasites of equids.

The research evaluated the effectiveness of moxidectin, a medication, in treating internal parasites in horses, using both critical and controlled testing methods. Different forms of moxidectin and dose levels were tested, with results indicating effectiveness against a variety of parasites, though the rate of success varied.

Methodology and Testing Procedure

• The tests were conducted in 1988 and 1989 using 40 horses in total. These were divided into 2 groups: one for critical tests and another for controlled tests, both including 20 horses each.
• Two different formulations of moxidectin were utilized: one as an injectable form for intramuscular or oral administration, and the other as an oral gel.
• The dose rates applied were 0.2, 0.3, or 0.4 mg per kilogram of body weight.
• The parasites treated with moxidectin included Gasterophilus intestinalis, Gasterophilus nasalis, Parascaris equorum, Strongylus vulgaris, Strongylus edentatus, and Oxyuris equi.

Test Results

• Removal rates for second instar G. intestinalis were 93-100%, although one batch of the injectable formulation yielded an 89% removal rate.
• For third instar G. intestinalis, G. nasalis, P. equorum, S. vulgaris and S. edentatus, the efficiency rate reached 100%.
• The only inconsistent results were noted for O. equi, with efficiency ranging from 27% to 100% depending on the formulation and dose rate.
• There were also local reactions observed at the injection site in three horses.
• No signs of toxicosis were noted in any of the horses.

Controlled Test Results

• In the controlled tests, dosage rates of 0.2 or 0.4 mg per kilogram of body weight were applied.
• The injectable formulation exhibited the highest removal rate of third instar G. intestinalis.
• Discrepant and incomplete effects were observed against O. equi using this method.
• Excellent removal rates were seen for Habronema muscae and migrating S. vulgaris and S. edentatus, although the treatment remained incomplete for S. vulgaris.
• Treatment was highly effective against S. vulgaris and S. edentatus, and cleared G. nasalis third instars and P. equorum completely in treated horses.