Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 1999
Publication Date: January 1, 2000
Interpretive Summary: There are eight named species of Cryptosporidium from fish, reptiles, birds, and mammals but only one species is infectious for most mammals including domestic livestock and humans - that is Cryptosporidium parvum. Because the microscopic stage found in the environment is extremely small and many species share surface antigens, it is difficult or impossible to differentiate species based on microscopic observation and fluorescent antibody methods. Molecular techniques have been developed for gene sequencing that permit differentiation of species and strains of Cryptosporidium. This manuscript review the techniques and the genes most helpful in epidemiologic investigations and clinical diagnoses, and indicates future research needs.
Antigenic analysis, isoenzyme analysis, PCR based characterization studies, random amplified polymorphic DNA analysis, and gene sequencing techniques for identification of species and strains of Cryptosporidium are reviewed. The value of sequencing the 18S rDNA gene versus the ITS1, 5.8S and ITS2 rDNA resions is discussed. The identity of species by sequence analysis of specific genes is compared. These include the acetylCoA synthase, b-tubulin, COWPl dihydrofolatereductase-thymidylate synthase (dhfr-ts), thrombospondin-related adhesion proteins (TRAP-C and -C2), and the heat shock protein (HSP) gene. Multilocus analysis is also reviewed. The problems and benefits in using these techniques is discussed relevent to environmental and clinical specimens. For these techniques to be applied problems of oocyst recovery, PCR inhibition by environmental products, speed of testing, and PCR extraction of amplifiable nucleic acids must be overcome. Benefits include clear identification of organism with extensive genetic diversity which will aid in decisions relative to public health policy and patient treatment.