(p. 536) Cryptosporidiosis 

Cryptosporidium species represent a genus of parasitic protozoa (Apicomplexa) that are transmitted via the faecal-oral route and commonly infect the epithelial tissues of the gastric or intestinal (or sometimes the respiratory) tract of many vertebrates, including humans. Infection occurs following the ingestion of viable and resistant oocysts, through direct host-to-host contact or in contaminated food, drinking or recreational water. Infection can be transmitted via anthroponotic (human-to-human, human-to-animal) or zoonotic (animal-to-human or animal-to-animal) pathways, depending upon the species of Cryptosporidium. Although infection can be asymptomatic, common symptoms of disease (cryptosporidiosis) include diarrhoea, colic (abdominal pain), nausea or vomiting, dehydration and/or fever. In humans, cryptosporidial infection in immunocompetent patients is usually short-lived (days to weeks) and eliminated following the stimulation of an effective immune response. However, infection in immunodeficient individuals (e.g., those with HIV/AIDS) can be chronic and fatal (in the absence of immunotherapy), as there are few effective anti-cryptosporidial drugs and no vaccines available. The present chapter provides an account of the history, taxonomy and biology, genomics and genetics of Cryptosporidium, the epidemiology, pathogenesis, treatment and control of cryptosporidiosis and the advances in tools for the identification and characterisation of Cryptosporidium species and the diagnosis of cryptosporidiosis.