Distribution and Genetic Characterizations of Cryptosporidium spp. in Pre-Weaned Dairy Calves in Northeastern China’s Heilongjiang Province

BACKGROUND Cryptosporidium spp. are common parasites of humans and animals. Farm animals, especially pre-weaned calves, are considered to be one of main animal reservoir hosts of Cryptosporidium in the transmission of human cryptosporidiosis. The aim of this study was to determine the distribution and genotypes of Cryptosporidium spp. in pre-weaned calves using molecular tools and to assess zoonotic transmission and elucidate the public health significance in northeastern China. METHODOLOGY/PRINCIPAL FINDINGS A total of 151 fecal specimens from pre-weaned calves were collected in Heilongjiang Province and were screened for Cryptosporidium by PCR. The average prevalence of Cryptosporidium was 47.68% (72/151). Cryptosporidium spp. were characterized by DNA sequencing of the small subunit (SSU) rRNA gene and the 60-kDa glycoprotein (gp60) gene. Based on the SSU rRNA gene, five Cryptosporidium spp. were identified, including C. bovis (n = 34), C. andersoni (n = 26), C. ryanae (n = 5), C. meleagridis (n = 5) and C. parvum (n = 2). The SSU rRNA nucleotide sequences were identical to each other, respectively, within C. ryanae, C. parvum, C. meleagridis and C. andersoni. Four types of C. bovis were found in the SSU rRNA gene, with two novel types. The gp60 gene was successfully sequenced in one C. parvum isolate and three C. meleagridis isolates, with IIdA19G1 for C. parvum and IIIeA22G2R1 for C. meleagridis. CONCLUSION/SIGNIFICANCE Molecular analysis indicates that Cryptosporidium spp. are endemic in pre-weaned calves in Heilongjiang Province. The findings of C. parvum and C. meleagridis suggested the possibility of zoonotic transmission and public health significance. The transmission dynamics of C. parvum and C. meleagridis needed to be clarified by further molecular epidemiologic studies from humans and animals. Whether calves could act as the natural reservoirs of C. meleagridis needed to be confirmed by more systematic experimental infection studies.