Research paperThe dynamics of Trichinella spiralis epidemiology: Out to pasture?

•Human trichinellosis is declining worldwide.•A major reason is the increase in controlled housing/management in commercial pig production.•Free-range pork may increase risk of pig infections due to spillover from reservoir hosts.•Knowledge on epidemiology of spillover risk is needed to assess risk for pastured pigs.

The great public health success in prevention of human trichinellosis has resulted in a decades-long decline in the incidence and health impact of this zoonosis. The important elements of this achievement include improvement in animal husbandry practices, meat inspection, consumer education, and medical care. Most outbreaks now involve consumption of infected game. However, domestic pork still accounts for many outbreaks, mostly in Eastern Europe and Argentina, where traditional small, “backyard” rearing of pigs for household and local use often involve high risk rearing practices, especially the feeding of food waste. Although commercially produced pork under controlled management now accounts for about half of the world's pork production the demand by consumers, especially in Europe and North America, for free-range pork is increasing. Because of the varying degrees of outdoor exposure in free-range systems, there is concern that such exposure increases the risk of spillover of Trichinella spiralis, (also Trichinella britovi and Trichinella pseudospiralis in Europe) from wild animal reservoirs. This review examines the knowledge gaps hindering the risk assessments needed to provide the producers with guidelines for achieving the food safety assurance demanded by consumers.