Phylogenetic analysis of Cryptosporidium parasites based on the small-subunit rRNA gene locus

Biological data support the hypothesis that there are multiple species in t he genus Cryptosporidium, but a recent analysis of the available genetic da ta suggested that there is insufficient evidence for species differentiatio n. In order to resolve the controversy in the taxonomy of this parasite gen us, we characterized the small-subunit rRNA genes of Cryptosporidium parvum , Cryptosporidium baileyi, Cryptosporinium muris, and Cryptosporidium serpe ntis and performed a phylogenetic analysis of the genus Cryptosporidium. Ou r study revealed that the genus Cryptosporidium contains the phylogenetical ly distinct species C. parvum, C. muris, C. baileyi, and C. serpentis, whic h is consistent with the biological characteristics and host specificity da ta. The Cryptosporidium species formed two clades, with C. parvum and C. ba ileyi belonging to one clade and C. muris and C. serpentis belonging to the other clade. Within C. parvum, human genotype isolates and guinea pig isol ates (known as Cryptosporidium wrairi) each differed from bovine genotype i solates by the nucleotide sequence in four regions, A C. muris isolate from cattle was also different from parasites isolated from a rock hyrax and a Bactrian camel. Minor differences were also detected between C. serpentis i solates from snakes and lizards. Based on the genetic information, a specie s- and strain-specific PCR-restriction fragment length polymorphism diagnos tic tool was developed.