Pastured pigs are vulnerable to Trichinella spiralis infection through exposure to wild reservoir hosts. To evaluate the potential impact of the expanding production of pork from pasture-raised pigs, we mapped locations of T. spiralis occurrence and pastured-pig farms in the United States. Twenty-eight farms were located within 50 km of previous infection. The incidence of Trichinella spiralis infection in humans and swine has declined markedly in North America over the past 20 years; however, sporadic outbreaks still occur (1,2). The importance of sylvatic reservoir hosts in the persistence of T. spiralis infection risk is well-documented, even in countries that have made substantial gains in controlling the infection in swine (2–5); T. spiralis infection has been recently demonstrated in foxes in Ireland, where no pig infections had been identified for 30 years, (6). The outdoor rearing of pigs is a major risk because of increased exposure to sylvatic and synanthropic hosts (2–10). Transmission of T. spiralis from infected farm pigs to synanthropic (e.g., rats, cats, raccoons) and local sylvatic animal populations also occurs (3,11). Pastured-pig operations in the United States have experienced substantial growth in recent years. The number of pigs reared in organic livestock operations, which by law must pasture pigs for at least some part of the day, rose from 1,724 in 2000 to 10,018 in 2005 (12). An even larger number of pigs (>100,000) are now being reared nonorganically on pasture and marketed as “pastured, humane, or free-range ” pigs. (See below for source of information.) Because of the sporadic occurrence and distribution of outbreaks, and the lack of routine monitoring, the impact of this increase on the risk for T. spiralis infection for pastured farm swine is unknown. We report the use of geographic information system (GIS) methods to locate potential highrisk foci to facilitate targeting of surveillance for domesti
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