EXPERIMENTAL ASCARIS-SUUM INFECTION IN THE PIG - WORM POPULATION-KINETICS FOLLOWING SINGLE INOCULATIONS WITH 3 DOSES OF INFECTIVE EGGS

To study population kinetics during primary Ascaris suum infections, 3 groups of 52 pigs each were inoculated with 100, 1000, or 10000 infec tive eggs. In all groups, the majority of larvae was found in the live r on day 3 post inoculation (p.i.) and in the lungs on day 7 p.i. Live r white spots, caused by migrating larvae, were most numerous at day 7 p.i., whereafter they gradually healed, and only low numbers of granu lation-tissue type white spots and lymphonodular white spots persisted at days 21-56 p.i. Independent of dose level, 47-58% of the inoculate d 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 s tarted earlier and removed a higher percentage of the worms with incre asing inoculation dose, resulting in small strongly aggregated worm po pulations by day 28 p.i. (k of the negative binomial distribution was low: 0.2-0.4) without significant differences between groups. Thus, ov erdispersion, which is a characteristic of both porcine and human asca rosis, is found here under experimental conditions where aggregation f actors like host behaviour, transmission rate, host status etc have be en partly or totally controlled.