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A total of 1,647 sheep fecal samples were screened in Western Australia for the presence of Cryptosporidium and Giardia spp. using microscopy. Analysis revealed that although both parasites were detected in a high proportion of samples, with the exception of one Cryptosporidium hominis isolate, the majority of isolates genotyped are not commonly found in humans.

Strategies that limit the development of gastrointestinal worms that are resistant to anthelmintics are essential for the sustainable control of worm infestations in sheep enterprises. These strategies involve maximizing the ability of sheep to withstand the effects of worms and reducing selection pressure for anthelmintic resistance among worms when anthelmintics are used. For sustainable use of anthelmintics, some non-resistant worms must survive either as adult worms in sheep or as worm larvae on pasture to dilute the population of anthelmintic-resistant worms and hence prevent rapid increases in resistance. However, in some situations it is necessary to allow worms to survive, which may reduce sheep productivity. The relative priorities for measures aimed at worm control and those aimed at prevention of anthelmintic resistance vary according to the goals of the enterprise, the level of the worm challenge and the capacities of various classes of sheep to tolerate worms. For instance, in prime-lamb production systems, worm control should take precedence over resistance prevention because rapid growth is of paramount importance. Well-nourished adult animals, which have strong resistance and resilience to worms, can be left untreated to combat the development of anthelmintic resistance. This article discusses guidelines for the management of worms in various sheep production systems and emphasizes a whole-farm management approach to anthelmintic resistance. [ABSTRACT FROM AUTHOR]