ABSTRACT
Protozoans of the genus Cryptosporidium are small (2-6 μding on stage in life cycle) coccidian parasites that infect the mucosal epithelium of a variety of animals, including humans (1-3). Until recently, infections with Cryptosporidium spp. were considered rare in animals, and in humans they were thought to be the result of an opportunistic pathogen of immunodeficient persons outside its normal host range (4-8). Our concept of this coccidian has changed within the past few years to that of a significant and widespread cause of gastrointestinal illness in several animal species, especially calves, lambs, and humans (1-3).
