Equine Internal Medicine Q&A 15

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Exploratory laparotomy was carried out on a 14-month- old Standardbred colt on the evidence of physical findings consistent with small intestinal obstruction. At surgery the findings were those illustrated in the image.

Question	Answer		Article
What is the diagnosis?	Small intestinal impaction with Parascaris equorum. Ascarid infection is common in equine animals less than two years old, after which a strong immunity to this parasite develops. The occurrence of ascarid, intestinal impaction is very rare.		Link to Article
What advice would you give to the owner of the colt?	Advice to the owner is: Treat any grazing cohorts of similar age with anthelmintic. Implement a parasite prophylaxis programme or modify the existing programme. Treat any grazing cohorts of similar age with anthelmintic. Parasitological features relevant to control of ascarids are: Adult worms are prolific egg producers. Ascarid eggs are thick-shelled and resilient in the environment. Although there is a potential risk of inducing further cases of ascarid impaction following treatment and death of large numbers of luminal worms, the probability of this is low. The drug of choice is either oral ivermectin (0.2mg/kg bodyweight) or oral fenbendazole (10mg/kg on five consecutive days). It will be necessary to repeat treatment at intervals of approximately 30 days as neither treatment regimen has high efficacy against immature ascarids early in migration. If possible, following treatment the group of animals should be grazed on pasture not used for young horses within the previous 12 months. As a result, in areas grazed by young animals with an inappropriate parasite prophylaxis programme it is likely that there will be a high level of transmission of parasites between horses. Ascarid prophylaxis is best achieved by interval dosing all animals from three months of age with either pyrantel (four weekly), benzimidazoles (six weekly) or ivermectin (6–8 weekly). Alternatively, control could be achieved with daily in-feed dosing with pyrantel but this product is not licensed in Europe. Ideally, owners and managers should avoid using the same grazing area year-on-year for their young, growing animals.		Link to Article