Persistent efficacy of moxidectin canine sustained-release injectable against experimental infections of Ancylostoma caninum and Uncinaria stenocephala in dogs.

: The efficacy of moxidectin canine sustained-release injectable administered at fixed intervals before administration of an oral hookworm challenge was evaluated in 40 laboratory dogs. Groups of eight dogs were treated with the moxidectin sustained-release formulation by SC injection approximately 3, 4, 5, or 6 months before being given oral inoculations with 300 Ancylostoma caninum larvae on Day 0 and 400 Uncinaria stenocephala larvae one day later. Dogs were euthanized 21 days after parasite inoculations. Fecal samples and the intestinal contents collected at necropsy from each dog were examined for hookworms. Fecal egg count reductions based on geometric means relative to controls were 99.2% (3 months) to 81.2% (6 months). The reduction in A. caninum worm recoveries at 3, 4, 5, and 6 months based on geometric means were 94.7%, 90.3%, 82.0%, and 60.2%, respectively. The mean reductions in U. stenocephala worm counts at these intervals were 94.6%, 85.3%, 71.6%, and 48.2%,respectively.