Abstract:

Objective To investigate the status of Cryptosporidium infection in imported breeding dairy cows in a dairy farm in Shenzhen, and analyze the molecular characteristics of Cryptosporidium isolates. Methods Fresh cow fecal samples were collected from a dairy farm in Shenzhen. Genomic DNA was extracted from the samples, and the small subunit ribosomal ribonucleic acid gene (SSU rDNA) of Cryptosporidium was amplified by nested PCR. The PCR products were sequenced and blasted to determine the genotype, and construct phylogenetic tree. Data were analyzed with Chi-square test using Graphad Prism 7.0. Results A total of 20 cow fecal samples were collected, including 5 from adult cows, 10 from weaned calves and 5 from pre-weaning calves. The PCR results showed that 8 samples were positive of Cryptosporidium, with positive rate of 40%, including 1 adult cow (1/5), 5 weaned calves (5/10), and 2 pre-weaning calves (2/5). Sequencing results showed that 2 Cryptosporidium genotypes were detected, including C. ryanae (n = 5) and C. bovis (n = 3). The C. ryanae infection was found in all age groups. After blasting with the SSU rDNA gene of C. ryanae, four of the five isolates of C. ryanae were 100% similar to the SSU rDNA gene (KT922233) of bovine-borne C. ryanae from Ethiopia, and the other one was similar to that of the isolate of C. ryanae (HQ179574, 99.9%) from Northeast China. The three isolates of C. bovis were 100% similar with the SSU rDNA gene (KT922231) of bovine-borne C. bovis from Ethiopia. After constructing the phylogenetic tree of C. ryanae based on the sequence of SSU rDNA gene, the sequences of C. ryanae and C. bovis were in two branches, which were consistent with the same isolated Cryptosporidium species in different regions. Conclusion Cryptosporidium infection is common in this dairy farm in Shengzhen, with C. ryanae as a dominant species in infection.

Key words: Cryptosporidium ryanae, Cryptosporidium bovis, SSU rDNA, Dairy cattle, Shenzhen City