Trichinella spiralis in an agricultural ecosystem. II. Evidence for natural transmission of Trichinella spiralis spiralis from domestic swine to wildlife.

Epidemiological investigations of an outbreak of trichinellosis were carried out in a domestic swine herd and it was established that the parasite also occurred in rats, and in skunks, opossums, and raccoons. Because considerable uncertainty exists regarding the role of sylvatic trichinellosis as a reservoir for the synanthropic cycle, studies were conducted to determine the genetic nature of the various isolates from this ecosystem. Pig infectivity trials, isoenzyme analyses, and repetitive DNA sequence analyses were performed. The results showed that all isolates from the farm environs were genetically similar and that they are related to Trichinella spiralis isolated from domestic pigs. The implication of these findings, in contrast to studies on isolates from wildlife elsewhere, is that this parasite is transmitted from domestic swine to sylvatic hosts and that any control or eradication efforts must take into account the potential for reinfection of hogs from wild animals.