Comparative long-term efficacy of ivermectin and moxidectin over winter in Canadian horses treated at removal from pastures for winter housing.
The impact of a late fall treatment on the spring rise of fecal egg counts was evaluated in a controlled study with Canadian horses treated with 2 different dewormers immediately after removal from pasture for winter housing. The horses were stabled until the end of the trial period. Seventeen weanlings, 20 yearlings, and 15 2-year-old horses located in Ontario, which were presumed to be naturally infected with cyathostomins after pasture grazing, were randomly allocated to either a group treated with 0.4 mg/kg of moxidectin and 2.5 mg/kg of praziquantel or a group treated with 0.2 mg/kg of ivermectin and 1.5 mg/kg of praziquantel. Three weeks after treatment, all strongyle fecal egg counts were reduced to zero for both treatment groups. However, at 5 months post-treatment, mean geometric fecal egg counts were statistically higher for the yearlings and 2-year-old horses treated with ivermectin than for the yearlings and 2-year-old horses treated with moxidectin (P < 0.0001).
Wyeth Animal Health, 400 Michener Road, Guelph, Ontario, N1K 1E4. jelsener@wyeth.com
Johanne
J
Elsener
Alain
A
Villeneuve
D000367:Age Factors; D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology*; D004338:Drug Combinations; D004351:Drug Resistance; D005243:Feces / Q000469:parasitology*; D005260:Female; D006736:Horses; D006799:Housing, Animal; D007559:Ivermectin / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology; D008297:Male; D009864:Ontario; D010270:Parasite Egg Count / Q000662:veterinary*; D006109:Poaceae; D011897:Random Allocation; D012621:Seasons; D013319:Strongyle Infections, Equine / Q000188:drug therapy* / Q000469:parasitology / Q000517:prevention & control; D013997:Time Factors; D016896:Treatment Outcome
D000977:Antiparasitic Agents; D004338:Drug Combinations; D018942:Macrolides; D007559:Ivermectin; C027837:moxidectin