Sylvatic and domestic Trichinella spp. in wild boars; infectivity, muscle larvae distribution, and antibody response.

Thirty-six wild boars were inoculated with Trichinella spiralis, Trichinella nativa, Trichinella britovi, Trichinella pseudospiralis (USSR), T. pseudospiralis (USA), T. pseudospiralis (AUST), Trichinella murrelli, Trichinella T6, and Trichinella nelsoni. The wild boars were killed at 5 and 10 wk postinoculation (PI), and the number of muscle larvae per g (lpg) of tissue was determined for 18 muscles or muscle groups. Five weeks PI, all Trichinella genotypes had established as muscle larvae, but their infectivity varied widely: T. spiralis established in high numbers (mean = 296 lpg), T. britovi, T. nelsoni, and 1 of the T. pseudospiralis genotypes (AUST) in moderate numbers (mean = 53-74 lpg), whereas the remaining genotypes were poorly infective (mean 2-16 lpg). Because of considerable weight gain of the wild boars, an estimated total larval burden (live weight x lpg) was calculated for each animal. The total larval burden did not change significantly over time for T. spiralis, T. murrelli, T. britovi, T. nelsoni, and T. pseudospiralis (USA and USSR), whereas a significant reduction could be demonstrated for T. nativa, Trichinella T6, and T. pseudospiralis (AUST). Diaphragm and tongue were predilection sites in wild boars, independent of Trichinella genotype and infection level. At low infection levels, a greater percentage of larvae were found in diaphragm and tongue at 10 wk than 5 wk PI. Antibody responses increased rapidly between weeks 3 and 5 PI. For T. spiralis and T. nelsoni, the high antibody level persisted throughout the experimental period, but for T. nativa, T. britovi, T. murrelli, or Trichinella T6, the levels declined. For T. pseudospiralis, the antibody response increased more gradually between weeks 3 to 10 PI. Infection with all genotypes of Trichinella were detected using any of 7 excretory-secretory antigens, which points to the potential use of 1 common antigen for epidemiological studies on Trichinella in wild boars. In conclusion, T. spiralis is highly infective to wild boars, T. britovi, T. nelsoni, T. pseudospiralis (USA), and T. pseudospiralis (USSR) are moderately infective, and T. nativa, T. murrelli, T. pseudospiralis (AUST), and Trichinella T6 are poorly adapted to this host species.