Efficacy of ivermectin against experimental and natural infections of Gasterophilus spp in ponies.
Antiparasitic efficacy of ivermectin against migrating Gasterophilus intestinalis was evaluated in 36 treated and 24 nontreated (n = 12) or vehicle-treated (n = 12) ponies experimentally and naturally infected with G intestinalis and naturally infected with G nasalis. Each pony was experimentally infected with 500 G intestinalis 1st instars in 2 divided doses on days -14 and -7 before treatment. On day 0, ivermectin was administered at the rate of 200 micrograms/kg of body weight by IV (n = 12) or IM injection (n = 12) or given as an oral paste (n = 12). Ponies were euthanatized and necropsied 21 days after treatment. In each nontreated or vehicle-treated pony, late 1st-, 1st- to 2nd- instar molt, and early 2nd-instars of G intestinalis were found in the mouth, and 2nd- and 3rd instars of G intestinalis and 3rd instars of G nasalis were found in the stomach. Bots were not found in any ivermectin-treated pony and, thus, ivermectin was 100% effective against oral and gastric stages. Adverse reactions were not observed in ponies given ivermectin by IM injection or orally, but 1 pony given the vehicle IV and 1 pony given ivermectin (in the vehicle) IV had an anaphylactic reaction, resulting in death of the ivermectin-treated pony. It was speculated that the adverse reaction was caused by histamines released in response to vehicle components given by IV injection.
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Sandhill Equine Center, Southern Pines, NC 28387.
D000818:Animals; D004175:Diptera / Q000187:drug effects; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy* / Q000469:parasitology; D006736:Horses / Q000469:parasitology; D007559:Ivermectin / Q000627:therapeutic use*; D007814:Larva / Q000187:drug effects; D008297:Male; D010272:Parasitic Diseases / Q000188:drug therapy; D010273:Parasitic Diseases, Animal; D013045:Species Specificity
D007559:Ivermectin