Seasonal monitoring of Cryptosporidium species and genetic diversity in neonatal dairy calves on two large-scale farms in Xinjiang, China

Background: Neonatal dairy calves infected with Cryptosporidium can possess a significant source of zoonotic infections and disease. To assess seasonal variations in the prevalence and genetic diversity of Cryptosporidium in neonatal dairy calves, 380 fecal samples from neonatal dairy calves on two large-scale farms in Xinjiang (Alaer and Wensu) were screened for the Cryptosporidium small subunit (SSU) rRNA gene. Results: : The overall prevalence of Cryptosporidium was 48.7% (185/380): 48.6% (108/222) in Alaer and 48.7% (77/158) in Wensu. Cryptosporidium was most frequent in summer (56.8%, 54/95), followed by spring (50.0%, 44/88), winter (46.8%, 44/94), and autumn (41.7%, 43/103) ( P > 0.05). Cryptosporidium was significantly more prevalent in calves with diarrhea (72.4%, 113/156) than in those without (32.1%, 72/224) ( P < 0.01). Based on a restriction fragment length polymorphism (RFLP) analysis, C . parvum (n = 173), C . bovis (n = 7), C . ryanae (n = 3), and co-infections of the three species (n = 2) were identified. Most (172/175) C . parvum samples were successfully sequenced at the 60-kDa glycoprotein gene ( gp60 ), revealing two zoonotic subtypes: IIdA14G1 (n = 94) and IIdA15G1 (n = 7) in Alaer and IIdA15G1 (n = 71) in Wensu. Conclusions: : These results showed that neonatal dairy calves were commonly infected with Cryptosporidium throughout the year, and there was a significant association between the occurrence of diarrhea and Cryptosporidium infection. Presence of IIdA14G1 and IIdA15G1 indicated neonatal dairy calves may be a source of zoonotic C . parvum subtypes.