Ovine haemonchosis : a review and report of epizootics in north west Western Australia and of a trial at Esperance, Western Australia

Ovine haemonchosis occurred in the arid environment of north west Western Australia during 1965 and 1972. Weather data for the period 1963 to early 1972 are examined and it is concluded that the hot, dry summer months are unsuitable for development and survival of free-living Haemonchus contortus. It is suggested that sheep should be treated with anthelmintic after unseasonally wet winters. From a trial at Esperance results suggest that two generations of worms may occur at Esperance each year - one in au mn and one in spring, with spring populations being larger than autumn populations. It is suggested that drenching sheep twice during summer with anthelmintic, and again during March may reduce the size of the autumn worm generation