Survival of Macracanthorhynchus ingens in swine and histopathology of infection in swine and raccoons.

Animal husbandry aimed at preventing Macracanthorhynchus hirudinaceus infections in swine is not successful in preventing exposure to Macracanthorhynchus ingens, and it is probable that pigs occasionally acquire acanthocephalans of that species. In some pigs, M. ingens survived 2 weeks and grew several millimeters. In such cases, destruction of villi, erosion of epithelium, leukocytic infiltration, and altered cytological structure at attachment sites accompanied the infection. Penetration was limited to the submucosa, and the effects were not as severe as those occurring in the presence of M. hirudinaceus, which enters the muscularis.