To study population kinetics during primary Ascaris suum
infections, 3 groups of 52 pigs each were inoculated with 100,
1000, or 10000 infective eggs. In all groups, the majority of larvae was
found in the liver on day 3 post inoculation (p.i.)
and in the lungs on day 7 p.i. Liver white spots, caused by migrating
larvae, were most numerous at day 7 p.i., whereafter
they gradually healed, and only low numbers of granulation-tissue type
white
spots and lymphonodular white spots
persisted at days 21–56 p.i. Independent of dose level,
47–58% of the inoculated eggs were recovered as larvae in the small
intestine on day 10 p.i., but most larvae were eliminated at days
17–21 p.i. This elimination started earlier and removed
a higher percentage of the worms with increasing inoculation dose,
resulting in small strongly aggregated worm
populations by day 28 p.i. (k of the negative binomial distribution
was low: 0·2–0·4) without significant differences between
groups. Thus, overdispersion, which is a characteristic of both porcine
and human ascarosis, is found here under
experimental conditions where aggregation factors like host behaviour,
transmission rate, host status etc have been partly or totally controlled.