There are two trematodes with an impact on human health that are endemic in Canada. Metorchis conjunctus infects fish, commonly the sucker, Catostomus commersoni. When an
infected fish is eaten this fluke ascends the common bile duct and intra-hepatic bile ducts, which results in an acute illness of abdominal pain, anorexia, and low grade fever associated with a marked peripheral eosinophilia (MacLean et al. 1996). In native (aboriginal) communities where this fish is occasionally consumed raw, impressive levels of asymptomatic infection (up to 20%) have been noted in stool parasite surveys. A second endemic trematode problem is 'swimmers' itch', a short-lived itchy dermatitis caused by the cercaria of duck schistosomes. The distribution of the problem, which is found across Canada, is not well delineated but is focal, with certain lakes developing a reputation for the nuisance.
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