Genetic diversity within Cryptosporidium parvum and related Cryptosporidium species

To assess the genetic diversity in Cryptosporidium parvum,,ve have sequence d the small subunit (SSU) rRNA gene of seven Cryptosporidium spp., various isolates of C. parvum from eight hosts, and a Cryptosporidium isolate from a desert monitor. Phylogenetic analysis of the SSU rRNA sequences confirmed the multispecies nature of the genus Cryptosporidium, with at least four d istinct species (C. parvum, C. baileyi, C, muris, and C. serpentis). Other species previously defined by biologic characteristics, including C. wrairi , C. meleagridis, and C. felis, and the desert monitor isolate, clustered t ogether or within C. parvum. Extensive genetic diversities were present amo ng C. parvum isolates from humans, calves, pigs, dogs, mice, ferrets, marsu pials, and a monkey. In general, specific genotypes were associated with sp ecific host species. A PCR-restriction fragment length polymorphism techniq ue previously developed by us could differentiate most Cryptosporidium spp. and C. parvum genotypes, but sequence analysis of the PCR product was need ed to differentiate C.,wrairi and C. meleagridis from some of the C. parvum genotypes. These results indicate a need for revision in the taxonomy and assessment of the zoonotic potential of some animal C. parvum isolates.