Migrations of trichostrongyle infective larvae experiments with ovine parasites in soil.

Experiments were done in natural and laboratory conditions with ovine Trichostrongyle species by depositing infective larvae on the top or inside a tube filled with soil. After different periods, extractions were done from soil samples taken after every 5 cm. Patterns of larval positions in the soil layers were similar for the 4 species in the experiments, though numbers of recovered larvae were not similar. In outdoor conditions at the end of winter, larvae could migrate from the surface to 40 cm depth or more in two weeks even if soil temperature was as low as 6 degrees C. These downward migrations seemed mainly due to water percolation through soil. Active migrations through soil were favoured according to the amount of soil water content but larvae had the ability to actively migrate upwards even in relatively dry conditions.