Abstract
At present, at least 10 species of Cryptosporidium are regarded as valid on the basis of differences in oocyst morphology, site of infection, and vertebrate class specificity: C. muris which infects rodents, C. andersoni which infects cattle; C. parvun which infects humans and other mammals; C. meleagridis and C. baileyi in birds; C. serpentis in reptiles; C. saurophilum in lizards; C. nasorum in fish, C. wrairi from guinea pigs and C. fells in cats. Molecular characterisation studies have detected considerable evidence of genetic heterogeneity between isolates of Cryptosporidium from different species of vertebrate and within C. parvum, and there is now mounting evidence suggesting that a series of host-adapted cryptic species of the parasite exist.