Detection of natural Trichinella murrelli and Trichinella spiralis infections in horses by routine post-slaughter food safety testing

Trichinella spiralis typically infects domestic swine, wild boar and occasionally horses, has a cosmopolitan distribution, and consequently is most frequently associated with food-borne outbreaks of trichinellosis in humans. Trichinella murrelli is typically found in wild carnivores in temperate areas of North America, where it has been responsible for outbreaks of human trichinellosis due to consumption of infected wild game. There has previously been only indirect evidence of natural infection with T. murrelli in a horse originating from Connecticut and implicated in an outbreak of trichinellosis in France in 1985. We describe a T. murrelli infection detected during routine testing of a horse from the USA imported to Canada for slaughter and export to the European Union (EU). Approximately 5 or more larvae per gram were recovered from digested tongue and diaphragm samples and identified as T. murrelli by PCR. This case provides the first direct evidence of naturally acquired T. murrelli infection in a horse, and further supports the potential food safety risk posed by this parasite species. It is the first instance in Canada of the detection of a Trichinella-infected horse via routine post-mortem testing. Trichinella spiralis-infected horses have been similarly detected by regulatory testing in France, and further details of two such previously reported cases are also provided here. The cases described herein underscore the importance of continued vigilance in quality assured food safety testing of horse meat to mitigate the risk of human trichinellosis.