Oxfendazole: activity of a two-dose treatment regimen on natural infections of internal parasites of equids, with emphasis on migrating large strongyles in controlled tests in 1986 and 1987.

Oxfendazole paste formulation was administered intraorally at a dosage of 10 mg/kg of body weight, twice (48 hours between treatments) in 5 controlled tests (experiments A, B, C, D, and E) to 18 equids (14 horses and 4 ponies) that were 5 to 24 months old in 1986 and 1987. Activity was evaluated against naturally acquired infections of various internal parasites, with emphasis on migratory stages of Strongylus vulgaris and S edentatus. The number of treated and nontreated equids in each experiment (horses in experiments A to D and ponies in experiment E) was: A, 1 and 1; B, 3 and 3; C, 3 and 1; D, 1 and 1; and E, 2 and 2, respectively. At 28 to 39 days after the first dose of the 2-dose treatment regimen, the equids were euthanatized and examined for several species of internal parasites. On the basis of the number of specimens at necropsy, excellent activity was found against migrating (retroperitoneal) S edentatus. In the aggregate for the 5 experiments, 41 live specimens of S edentatus were recovered from 10 treated equids, compared with 810 live specimens from the 8 nontreated equids, reflecting a difference of 95%. Several dead S edentatus were found in 8 treated equids. Three to 82 semihard nodules, which we believed were S edentatus-related lesions, were found in treated horses; only soft, seroedematous lesions, typical of S edentatus infection, were found in nontreated equids. In the cranial mesenteric arteries, activity for migrating S vulgaris was good overall.(ABSTRACT TRUNCATED AT 250 WORDS)