Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 4, 2000
Publication Date: December 1, 2000
Interpretive Summary: There are 10 valid species of Cryptosporidium but only C. parvum is widespread in humans and other mammals. Contamination of drinking water, food, and recreational water with human or animal feces has resulted in individual infections and in outbreaks affecting as many as 400,000 persons. Detection and identification of the fecal stage, the oocyst, is constantly improving. We can now recognize human and bovine genotypes of C parvum by isoenzyme analysis and by RAPD, RFLP, and sequence analysis. Because C. parvum in mammals has been identified primarily only by microscopy, biochemical and molecular methods will help to identify other species hidden under the C. parvum umbrella. Of the few molecular studies of Cryptosporidium isolated from immunocompromised persons most were found to be C. parvum human and cattle genotypes. A few were the dog genotype and some others had C. felis or C. meleagridis. Complicating our understanding gof host susceptibility, healthy persons were found infected with what appeared to be C. muris and the C. parvum human genotype has been found in a sea mammal. Biological studies of host ranges for species and genotypes of Cryptosporidium provide a practical correlation for molecular data. Information of both types is needed to clearly understand the epidemiology of this genus.
There are 10 valid species of Cryptosporidium and perhaps other cryptic species hidden under the umbrella of Cryptosporidium parvum. The oocyst stage is of primary importance for the dispersal, survival, and infectivity of the parasite and is of major importance for detection and identification. Because most oocysts measure 4 to 6 micrometers, appear nearly spherical, and have obscure internal structures, there are few or n morphometric features to differentiate 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 150 species of mammals reported to be infected with C. parvum or an indistinguishable organism very few oocysts have ever been examined using more than one of these tools. This paper indentifies the valid species of Cryptosporidium, their hosts and morphometrics; the reported hosts for the human pathogen, C. parvum; the mechanisms of transmission; the drinking water, recreational water, and foodborne outbreaks resulting from infection with C. parvum; and the microscopic, immunological, and molecular methods used to detect and identify species and genotypes.