This paper reports on the influence of maternal exposure to Ascaris suum on worm burden distributions in experimentally
infected piglets. In the first study, sows were inoculated before and during gestation (6 months, long-term exposure) with
10000 A. suum eggs twice weekly. In a second study, sows were inoculated during gestation only (3 months, short-term
exposure) with increasing doses of eggs (10000–40000 eggs twice weekly). Helminth-naive sows served as controls in both
studies. The third study used the same design as the short-term exposure study, but piglets from exposed and control sows
were cross-suckled within 4 h of birth before colostrum uptake. All piglets were inoculated 2 or 3 times with 50 A. suum
eggs on days 4 and 7 (and 14) after birth, and left with the sows. At 10 weeks of age all piglets were necropsied, and liver
lesions and worm burdens were recorded. Surprisingly, in piglets born to long-term exposed sows, the prevalence of A.
suum infection and the mean worm burden were significantly higher than those in piglets from control sows. In contrast,
neither worm burdens nor prevalence were significantly different between piglets from short-term exposed sows compared
with their controls. In the cross-suckling experiment, 67% of piglets suckling control sows harboured worms at slaughter,
compared with 15%of piglets suckling exposed sows. Maximum likelihood analysis of worm burden distribution and the
degree of parasite aggregation showed 3 distinctly different types of overdispersed distributions: worm counts in piglets
from control sows, in piglets from short-term exposed sows and in piglets from long-term exposed sows. When the worm
burden data were analysed including the cross-suckled piglets by biological mother, it appeared that the control and short-term distributions converged and that only the long-term exposure was significantly different. Overall, the degree of
parasite aggregation in piglets infected with A. suum decreased with exposure of the sows. A non-linear relationship was
observed between prevalence of infection and mean worm burden, which was different for piglets from exposed and
control sows, and similar to relationships of this type that previously have been found in human A. lumbricoides infections.
It was concluded that in porcine A. suum infections maternal exposure alters the distribution of worms in their offspring,
in which the duration of exposure appeared to be an important influence. The results of the cross-suckling further suggest
that maternal factors, e.g. antibodies, are transferred via colostrum.