LAUSR

Cryptosporidium parvum is a major zoonotic pathogen responsible for outbreaks of severe diarrhea in humans and calves. Almost all investigations of cryptosporidiosis outbreaks caused by C. parvum have focused on its IIa subtype family in industrialized nations. From December 2018 to April 2019, approximately 200 neonatal calves on a large cattle farm in Hebei Province, China were diagnosed with watery diarrhea and over 40 died. To investigate the cause of the outbreak fecal samples were taken during and after the outbreak from neonatal calves of ≤ 4 weeks of age (n = 40 and n = 56) and older calves of 4 - 24 weeks of age (n = 79 and n = 38). A total of 18 fecal samples collected from ill calves at the peak of the outbreak were analyzed for four common enteric pathogens using an enzymatic immunoassay (EIA). In addition, 75 samples from neonatal calves were tested for rotavirus by EIA. All samples were analyzed for Cryptosporidium spp. using PCR and sequencing techniques. Of the initial 18 samples from sick calves, ten were positive for C. parvum, five for rotavirus, and one for coronavirus. The overall prevalence of rotavirus in neonatal calves was 20.0% (15/75), with no significant differences during and after the outbreak. In contrast, Cryptosporidium parvum infections were significantly higher during the outbreak (60.0%, 24/40) than after the outbreak (30.4%, 17/56; P = 0.004). Cryptosporidium parvum infection was associated with the presence of watery diarrhea in neonatal calves (OR = 11.19), while no association was observed between C. bovis infection and diarrhea. All C. parvum isolates were identified as subtype IIdA20G1. This is one of the few reports of outbreaks of severe diarrhea caused by C. parvum IId subtypes in calves. More attention should be directed toward the dissemination of C. parvum in China.