Infectivity, predilection sites, and freeze tolerance of Trichinella spp, in experimentally infected sheep

A total of 36 sheep in groups of 4 were inoculated with 9 isolates of Trich inella and euthanized after 10 weeks. Thereafter, numbers of muscle larvae were determined in 13 different muscles/muscle groups. Muscle larvae were f ound in high numbers in all four sheep inoculated with T. spiralis, in lowe r numbers in two sheep inoculated with T. pseudospiralis (USA isolate), and in very low numbers in one sheep inoculated with T. pseudospiralis (USSR i solate) and one inoculated with T. britovi. In infections of high and moder ate larval intensity, predilection sites of T. spiralis were the masseter m uscles, the tongue, and the diaphragm and those of T. pseudospiralis were t he masseter muscle and the neck. In low-intensity infections, muscle larvae were detected only in the diaphragm or in pooled muscle samples. For evalu ation of the freeze tolerance of the different Trichinella species in sheep -muscle tissue, samples taken from the filet were stored at + 5 degrees, -5 degrees, and -18 degrees C, respectively. After exposure for 1 and 4 weeks the tissue was digested and the released larvae were inoculated into mice for determination of the reproductive capacity index (RCI). Larvae of both T. spiralis and T.pseudospiralis survived freezing at -5 degrees and -18 de grees C for 4 weeks.