Efficacy of moxidectin against a strain of Ostertagia spp resistant to ivermectin, albendazole and levamisole

The efficacy of a new antiparasite drug moxidectin (Cydectin injectable 1%, Cyanamid) against multiple resistant gastrointestinal nematodes of Ostertagia spp. was studied on 16 lambs experimentally infected each with 7,000 larvae. A single subcutaneous application of 0.2 mg.kg(-1) of moxidectin reduced the number of nematode eggs in faeces by 99.6% and the number of worms at helminthological dissection by 99.9% as compared with untreated lambs. Of the adult worms found in abomasa, 91% were identified as Ostertagia circumcincta and 9% as Ostertagia trifurcata.