Submitted to: American Society of Tropical Medicine and Hygiene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 1998
Publication Date: N/A
Interpretive Summary: Large concentrations of swine produced intensively year round have become the rule for pig farms in most developed countries. The presence of a large percentage of these pigs being infected with the large round worm, Ascaris suum, is a threat to public health because the worm is infectious for humans. Little current information is available about infections of humans with Ascaris derived from pigs. However, recent clinical outbreaks of parasite infections in Japan and Holland implicate pig Ascaris as responsible for human disease. The current study was designed to examine an infection of a non-human primate with pig-derived Ascaris in order to determine severity and location of the infection. It was found that pig-derived Ascaris will migrate and develop in the monkey, as has been suggested from some inadvertent infections of humans. The intensity of clinical disease is rather mild except for lesions detected in the liver and lungs. There is, however, the threat of more severe disease with multiple exposures or with combined infections with other worms that exist in the environment. This information will be helpful to public health officials and pig producers that are concerned with contamination of their surroundings with parasite eggs.
Confinement-reared Erythrocebus patas monkeys were inoculated with A. suum eggs to observe clinical effects, migration and development of larvae, and immunity to infection in a primate model of human infection. Parasitic larvae were detected in tissues predicted from normal migration in swine. However, the larvae in monkeys were delayed in development and kinetics compared to swine, and fourth-stage larvae and a fifth-stage young adult were detected at an aberrant site in the ileal/cecal region of the small intestine. Moderate portal infiltration and eosinophilic granulomas were detected histologically in the E. patas livers compared to intense septal fibrosis in the pig livers; perivascular and peribronchial infiltration and pleural thickening were observed in both hosts. Oral inoculation of Ascaris eggs derived from pigs into a heterologous primate host results in hepatic-pulmonary- intestinal migration with inefficient development to adult worms; lesions in the organs are microscopic indicating generally subclinical disease but a strong protective immunity. This response does not strictly fit the definition of a visceral larva migrans. eggs.