Epidemiology of Cryptosporidium: transmission, detection and identification

There are 10 valid species of Cryptosporidium and perhaps other cryptic spe cies hidden under the umbrella of Cryptosporidium parvum. The oocyst stage is of primary importance for the dispersal, survival, and infectivity of th e parasite and is of major importance for detection and identification. Bec ause most oocysts measure 4-6 mum, appear nearly spherical, and have obscur e internal structures, there are feu or no morphometric features to differe ntiate species and in vitro cultivation does not provide differential data as for bacteria. Consequently, we rely on a combination of data from three tools: morphometrics. molecular techniques, and host specificity. Of 152 sp ecies of mammals reported to be infected with C. parvum or an indistinguish able organism, very few oocysts have ever been examined using more than one of these tools. This paper reviews the valid species of Cryptosporidium, t heir hosts and morphometrics; the reported hosts for the human pathogen, C. parvum; the mechanisms of transmission; the drinking water, recreational w ater, and food-borne outbreaks resulting from infection with C. parvum; and the microscopic, immunological, and molecular methods used to detect and i dentify species and genotypes. (C) 2000 Published by Elsevier Science Ltd. on behalf of the Australian Society for Parasitology Inc.