Relationship between rainfall distribution and the peak incidence of parasitic gastro-intestinal infective larvae on sheep pasture

Abstract

The numbers of invasive third stage larvae (L3) of the gastrointestinal parasitic nematodes of sheep on the pasture were studied on a farm in central Scotland in order to test the value of accumulated wetness units (Thomas, 1974) as a means of predicting the time of the occurrence of the summer peak.

An artificially watered area gave apparently favourable conditions for the development and migration of these larvae but did not significantly change the timing of the peak.

The peak occurred rather earlier than was predicted from the accumulated wetness units.