Development and infectivity of eggs and larvae derived from pigs trickle-infected with Oesophagostomum dentatum at different dose levels

We examined the impact of different Oesophagostomum dentatum dose levels an d durations of infection on the development and infectivity of the followin g generation. Pigs were trickle-infected with 200, 2,000 or 20,000 L-3/week over 20 weeks. Egg hatch assays were performed at monthly intervals; howev er, no consistent differences were found between any of the dose groups in the development of eggs into first-stage larvae. To compare larval infectiv ity, larvae were derived from faecal cultures set up from the low- and the high-dose groups in the early and the late part of the experiment, and were inoculated into helminth-free pigs (5,000 L-3/pig). Worm establishments we re significantly higher (P < 0.05) in the group of pigs receiving larvae de rived early in the experiment from the low-dose group compared with the two groups receiving larvae from high-dose groups, thus indicating an adverse effect of high doses of trickle infection on the later infectivity of L-3 l arvae derived from excreted eggs.