Molecular characterization of sylvatic isolates of Trichinella spiralis

Genetic relationships of 20 Trichinella isolates from Indiana wildlife were assessed and compared to Trichinella isolated from an infected swine herd. Trichinella larvae were isolated from coyotes, mink, raccoons, and red foxes. The larvae were maintained and amplified in white mice (ICR) and wild mice (Peromyscus leucopus). Differences in phenotypic characters of sylvatic isolates in the 2 laboratory hosts included an approximately 10-30-fold increase in parasite fecundity in wild mice. DNA for each isolate was extracted from Trichinella larvae and analyzed by dot-blot hybridization using a repetitive DNA probe pBP2 that recognizes DNA sequences specific for swine Trichinella. The probe hybridized only to Trichinella from swine and a single coyote isolate. Restriction endonucleases were used to digest DNA and the resulting fragments were separated by gel electrophoresis. Based on the presence of repetitive DNA sequences in the Trichinella genome, distinctive banding patterns were seen among the isolates. Trichinella isolated from swine had a pattern distinct from all sylvatic isolates except 1 from a coyote. Because this coyote was from the same general locality as the swine Trichinella outbreak, it was concluded that the isolate represents transmission of swine trichinellosis to the wildlife population. Further analysis using the enzyme Cla I identified unique banding patterns for wild isolates, suggesting that the sylvatic group is a genetically heterogeneous complex.