Availability of Haemonchus contortus L3 larvae on pasture at Kiboko: a semi-arid warm agro-climatic zone in Kenya

A study was carried out to determine the availability of Haemonchus contortus L3 larvae on pasture in a semi-arid warm agro-climatic zone of Kenya. By means of tracer sheep, it was shown that no H. contortus L3 larvae were available on pasture during the dry periods of the year (July–October and February). They were only available on pasture during the rainy season (November–January and March–June). Sheep permanently grazed on the same pasture however, harboured adult H. contortus in their abomasa throughout the year indicating that the perpetuation of haemonchosis in livestock in this agro-climatic zone was greatly dependent on the ability of the parasite to survive in the host throughout all seasons.