The relation of climate and topography to worm egg counts of gastro-intestinal nematodes of sheep in the Eastern Cape.

Haemonchus, Trichostrongylus, Ostertagia and Nematodirus worm populations of sheep based on differential egg counts are considered in relation to climatological and topographical data. Late spring, summer and early autumn rainfalls are related to ground slope to assess wetness. Egg counts indicated that the estimated worm populations in animals in flat areas with low rainfall were as heavy as or heavier than in animals on steep hilly areas with a high rainfall. It is proposed that tactical anthelmintic treatment be based on the degree of wetness of the grazing or farm.