Evaluation of the efficacy of a combination of imidacloprid and moxidectin against immature Toxocara cati in cats

A controlled laboratory study was conducted to evaluate the efficacy of a novel formulation of Imidacloprid and Moxidectin against fourth stage larvae and immature adult Toxocara cati infection in cats. Thirty-two, 8-week old Domestic Short Hair kittens were infected orally with ˜500 larvated Toxocara cati eggs on Day 0. On Day 14, the kittens were blocked by sex (16 male; 16 female), ranked by body weight, and allocated randomly to one of four treatment groups. Cats in Group 2 were treated topically on Day 14 with a formulation containing 10% Imidacloprid + 1.0% Moxidectin at dosages of 10 mg/kg and 1.0 mg/kg, respectively. Animals in Group 1 were treated topically on Day 14 with a placebo formulation containing excipients only. Groups 1 and 2 were necropsied on Day 19 for worm recovery. Groups 3 (placebo) and 4 (Imidacloprid + Moxidectin) were treated topically on Day 24 and necropsied for total worm counts on Day 29. At necropsy, alimentary contents and saline incubates of the small intestine were collected, preserved, and examined microscopically. Nematodes were recovered, counted, and identified to genus, species, and stage of development. Geometric mean counts of nematode developmental stages were calculated to determine the efficacy of each treatment. The combination of Imidacloprid + Moxidectin administered topically was 97.2% effective against fourth stage Toxocara cati larvae and 98.3% effective against immature T. cati adults. No systemic or local adverse reactions to treatment were observed.