Phylogenetic analysis of Cryptosporidium isolates from captive reptiles using 18S rDNA sequence data and random amplified polymorphic DNA analysis

Sequence alignment of a polymerase chain reaction-amplified 713-base pair r egion of the Cryptosporidium 18S rDNA gene was carried out on 15 captive re ptile isolates from different geographic locations and compared to both Cry ptosporidium parvum and Cryptosporidium muris isolates. Random amplified po lymorphic DNA (RAPD) analysis was also performed on a smaller number of the se samples. The data generated by both techniques were significantly correl ated (P < 0.002), providing additional evidence to support the clonal popul ation structure hypothesis for Cryptosporidium. Phylogenetic analysis of bo th 18S sequence information and RAPD analysis grouped the majority of repti le isolates together into 1 main group attributed to Cryptosporidium serpen tis, which was genetically distinct but closely related to C. muris. A seco nd genotype exhibited by 1 reptile isolate (S6) appeared to be intermediate between C. serpentis and C. muris but grouped most closely with C. muris, as it exhibited 99.15% similarity with C. muris and only 97.13% similarity with C. serpentis. The third genotype identified in 2 reptile isolates was a previously characterized 'mouse' genotype that grouped closely with bovin e and human C. parvum isolates.