Experimental Ascaris Suum Infection in Piglets

Piglets from 0–50 days of age were exposed to infective Ascaris suum eggs at dose levels varying from 50–10,000 eggs. A clear inverse relationship was found between the inoculated egg doses and the numbers of worms found in the intestine. Thus, piglets given doses of 1,000 5,000 or 10,000 A. suum eggs practically never acquired the infection, the mean percentage of worms established being 0.013 per cent of the administered egg dose. In contrast, when 500 eggs were inoculated, 1.4–5.4 per cent (mean: 2.9 per cent) of the egg dose was established, and with a dose of 50 eggs, 38–100 per cent (mean: 64 per cent) of the inoculated eggs completed their migration and established an intestinal worm population. Newborn piglets inoculated before they had suckled colostrum inhibited the infection as effectively as did older pigs. On the other hand, neonatal piglets did not show the distinct eosinophilia that developed at day 10 in older piglets receiving more than 500 eggs. The findings are dicussed with particular emphasis on the mechanisms involved in the massive elimination of migrating A. suum larvae following inoculation of large egg doses. Also, the epidemiological consequences of the reported findings are mentioned.