Common occurrence of a unique Cryptosporidium ryanae variant in zebu cattle and water buffaloes in the buffer zone of the Chitwan National Park, Nepal.

There are very few studies on the diversity and public health significance of Cryptosporidium species in zebu cattle and water buffaloes in developing countries. In this study, PCR-restriction fragment length polymorphism and DNA sequence analyses of the small-subunit (SSU) rRNA gene were used to genotype Cryptosporidium specimens from 12 zebu cattle calves, 16 water buffalo calves, and four swamp deer (Cervus duvaucelii) collected from the buffer zone of the Chitwan National Park, Nepal. All Cryptosporidium specimens from cattle and buffaloes belonged to Cryptosporidium ryanae, whereas those from deer belonged to Cryptosporidium ubiquitum. Comparison of the SSU rRNA gene sequences obtained with those from earlier studies has identified a nucleotide substitution unique to all C. ryanae isolates from Nepal, in addition to some sequence heterogeneity among different copies of the gene. The finding of the dominance of a unique C. ryanae variant in both zebu cattle and water buffaloes in Nepal indicates that there is unique cryptosporidiosis transmission in bovine animals in the study area, and cross-species transmission of some Cryptosporidium spp. can occur between related animal species sharing the same habitats.