COMPARATIVE EFFICACY OF MOXIDECTIN AND IVERMECTIN AGAINST HYPOBIOTIC AND ENCYSTED CYATHOSTOMES AND OTHER EQUINE PARASITES

Efficacies of moxidectin and ivermectin were compared in four groups o f eight ponies with natural parasite infections: placebo (Control), or al moxidectin gel at 0.3 mg kg-1 of body weight (Mox 0.3), oral moxide ctin gel at 0.4 mg kg-1 of body weight (Mox 0.4), and oral ivermectin paste at 0.2 mg kg-1 of body weight (Ivermectin). Fecal samples were t aken 0 and 2 weeks after treatment. Animals were necropsied and worms were collected 2 weeks after treatment. Moxidectin and ivermectin show ed similar efficacy (99%) against adult cyathostomes, Strongylus spp., Triodontophorus spp. and Habronema muscae. Both drugs were also more than 98% effective against luminal cyathostome and Oxyuris equi fourth stage larvae (L4). Neither drug was effective (0-10.1%) against hypob iotic early third stage cyathostome larvae (EL3). Moxidectin was moder ately effective (62.6-79.1%) in removing encysted cyathostome late thi rd stage larvae (LL3) and L4, whereas ivermectin was ineffective (0%) against these stages. By contrast, ivermectin was 95.4% effective agai nst Gasterophilus spp. third instar stage, whereas moxidectin was only 0-20.4% effective.