November 2012
Oral moxidectin more effective
by Susan Schoenian
Sheep & Goat Specialist
University of Maryland Extension
The efficacy of moxidectin administered by different routes, against naturally acquired infections of gastrointestinal nematode parasites of cattle, was compared using fecal egg count reduction tests on 14 commercial farms throughout New Zealand.
On each farm, groups of 15 calves were sampled for fecal nematode egg count and then treated with ivermectin administered orally, or with moxidectin administered either by the oral, subcutaneous injection, or topical (pour-on) route.
Samples were again collected 14 days after treatment and efficacy was calculated as the percentage reduction in group mean egg count between the pre- and post-treatment samples. In addition, efficacy was calculated for individual animals.
Averaged across all tests, the reduction in fecal egg count was significantly greater after treatment with moxidectin oral (91.1%) than following treatment with moxidectin injection (55.5%) or with moxidectin pour-on (51.3%). The oral treatments were significantly less variable in efficacy than the injection and pour-on treatments.
Based on these results, along with those of other studies, it is proposed that oral administration of macrocyclic lactone anthelmintics results in higher
concentrations of the active ingredient reaching the target worms in the gastrointestinal tract than following either administration by injection or by pour-on.
Source: J. Veterinary Parasitology, September 2012.
