Enteral and parenteral phases of Trichinella nativa and Trichinella pseudospiralis in the deer mouse, Peromyscus maniculatus.

Trichinella nativa and Trichinella pseudospiralis infections in a wild rodent host, the deer mouse (Peromyscus maniculatus), were characterized. Forty-six percent of 400 inoculated T. nativa were recovered on day 4 postinoculation (PI); 77% and 23% were found in the small and large intestines, respectively. Thirty-one percent of the worms recovered on day 4 remained in the large intestine beyond day 20 PI. Worms were embedded in the mucosa of the small intestine, cecum, and colon. Females recovered from the small and large intestines had statistically indistinguishable in vitro larval releases. Distension of the cecum and passage of loose stools were associated with the presence of worms in the large intestine. The ability of T. nativa to establish and thrive in the large intestine of deer mice was confirmed following intracecal implantation of first-stage larvae. On day 4 PI, 35% of 400 inoculated T. pseudospiralis were recovered, with 91% and 9% found in the small and large intestines, respectively. Although T. pseudospiralis established in the large intestine of deer mice, few worms remained beyond day 20. Females recovered from the small and large intestines had statistically indistinguishable in vitro larval releases. Although higher establishments of T. nativa (56% vs. 46%) and T. pseudospiralis (52% vs. 35%) were observed in CD-1 mice than in deer mice on day 4 PI, neither was able to colonize the large intestine of the former. The large intestine may be a more important habitat for adult trichinae than previously recognized.