Distribution of Trichinella spiralis larvae in selected muscles and organs of experimentally infected swine.

Thirty-two Hampshire-Yorkshire pigs (6 to 8 wk old) were inoculated with the Beltsville strain of Trichinella spiralis at a level of about 880 larvae/kg of body weight (about 15 kg). At about 100 kg, the pigs were slaughtered and 10-g samples of muscle and other tissues were digested in pepsin-HC1 and examined microscopically for T. spiralis larvae. The mean number of larvae recovered/gram was: tongue, 452; diaphragm, 391; obliquus abdominis internus, 130; serratus ventralis, 116; psoas major, 105; triceps brachii, 100; biceps femoris, 83; semitendinosus, 74; intercostal, 60; semimembranosus, 58 and longissimus dorsi, 37. The liver and spleen samples contained none. Larvae were found in one sample each of the blood, brain and kidney, in two samples of the heart, and in four samples of lymph tissue. Each of these samples was from a different pig except the positive samples of brain and heart, which were from the same pig. The larvae found in the blood, brain, kidney, heart and lymph were first stage larvae and, therefore, do not indicate migration of newborn larvae from the gut. The presence of these larvae in non-striated muscle tissue may have been due to contamination of the organs from infected skeletal muscle. These data confirmed previous reports of the distribution of the T. spiralis larvae among individual muscles of the carcass. Further, the data suggest that cross-contamination of organ tissue is possible during evisceration and, therefore, organ meat from infected swine cannot be assured to be free of T. spiralis larvae.