Cryptosporidium: from laboratory diagnosis to surveillance and outbreaks.

The burden of disease caused by the protozoan parasite Cyptosporidium is unknown. However, routine laboratory diagnosis and surveillance enables the basic epidemiology to be described, changes to be monitored and under-ascertainment to be measured. Although the two main species involved in human disease in developed countries, Cryptosporidium parvum and Cryptosporidium hominis, have differing epidemiologies and risk factors, national surveillance is generally from isolates identified to the genus level only. Enhancing the data by typing, at least to identify the isolates to the species level, removes some of the noise generated and better identifies the risks than when reports are not species-specific. This level of identification is also valuable for outbreak investigations, but further investigation of the population genetics of C. parvum and C. hominis is required for the development of more readily applied subtyping tools.