Inefficacy of moxidectin and doramectin against ivermectin-resistant<i>Cooperia</i>spp. of cattle in New Zealand

Abstract

Two cases are described in which strains of Cooperia spp. of cattle were found to be resistant to either the oral or the injectable formulations of ivermectin. Injectable moxidectin was not effective against the latter strain and doramectin was not effective against either of the ivermectin-resistant Cooperia isolates. In both cases, the anthelmintic efficacy of oral levamisole was 100%.