The epizootiology of nematode parasites of sheep in a high-rainfall area of Zimbabwe.

Fifty-two untreated lambs from a contaminated flock were slaughtered at regular intervals throughout the year, and their gastro-intestinal tracts were examined for the presence of nematode parasites. Haemonchus contortus and Oesophagostomum columbianum were found to be of major importance. The incidence of Haemonchus rose to a peak and remained at a high level throughout the winter through the fourth larval stages of the parasite predominated at this stage. Oesophagostomum columbianum was recovered in numbers unusually high for this species, the incidence of which remained at a relatively high level from March until October. The minor genera recovered were Trichostrongylus spp., Cooperia spp., Strongyloides papillosus and Trichuris ovis.