Merck Manual

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Pet Owner Version

Trichinellosis (Trichinosis) in Horses


Bert E. Stromberg

, PhD, Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota

Reviewed/Revised May 2019 | Modified Oct 2022

Trichinellosis is a parasitic disease that can be transmitted to people. It is caused by the nematode Trichinella spiralisand is widely distributed in temperate regions. Other Trichinella species cause disease in more limited geographic areas.. People become infected when they eat insufficiently cooked infected meat, usually pork or bear, although meat from other animals has also been implicated. Natural infections occur in wild carnivores, and most mammals are susceptible. Trichinellosis has occasionally been found in horses.

Generally, there are no signs of the disease in horses. Making sure that ingestion of viable Trichinella cysts in muscle does not occur is the best way to prevent disease in both animals and humans. As herbivores, horses are less likely to naturally or inadvertently swallow Trichinella cysts, but there have been cases in which horses were fed food waste contaminated with infective cysts. This practice has led to human infections after consumption of infected horsemeat. In Europe, horsemeat intended for human consumption is inspected to remove contaminated meat from the food supply. Freezing meat cannot be relied upon to kill the cysts except in pork. Cooking meat to appropriate temperatures can kill cysts, if present. Undercooked or raw meat may not be safe.

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