Sustainable internal parasite control of sheep in Australia

Within Australia, sheep are managed under diverse conditions. Because of considerable differences between these areas, it is difficult to make universal recommendations about what constitutes a ‘sustainable’ worm control programme, although some broad principles apply. However, to be effective and profitable in the longer term programmes should cost-effectively prevent unacceptable production losses, but also avoid practices that encourage rapid selection for anthelmintic resistance. Recently, the practice of treating sheep with anthelmintics onto areas known to have low residual populations of worm larvae (low ‘refugia’) has been highlighted as a way of increasing selection for anthelmintic resistance. Consequently, a variety of strategies to increase refugia populations have been proposed. These strategies will vary considerably according to the patterns of infection, predominant parasites and distribution of rainfall in a given area, and key inputs to the farming system, such as the cost of labour.