Experimentally induced resistance to Ascaris suum in pigs.

The present study shows that oral inoculation with infective A. suum eggs or 3rd stage larvae in pigs aged 5-16 weeks induces resistance against oral challenge with infective A. suum eggs. Acquired resistance is reflected by an adaptive type of host response as measured by increased pathological, serological and hematological responses and decreased recovery of worms from lungs and small intestine. Although based on a limited number of experimental pigs, the results of the present experiments suggest that resistance to A. suum may be induced both when the parasites are introduced directly into the digestive tract as 3rd stage larvae, i.e. without a previous migration through the liver and lungs, and when given as infective eggs.