Cryptosporidiosis caused by Cryptosporidium parvum subtype IIdA15G1 at a dairy farm in Northwestern China

BACKGROUND: Cryptosporidium spp. are zoonotic parasites responsible for diarrhoeal diseases in animals and humans worldwide. Cattle are the most common mammalian species in which Cryptosporidium is detected, with pre-weaned calves considered to be reservoirs for zoonotic C. parvum. In October 2013, severe diarrhoea was observed in 396 pre-weaned calves at a farm in the Ningxia Autonomous Region of Northwestern China. 356 of the infected calves died despite antibiotic therapy. FINDINGS: 252 faecal samples were collected from the investigated farm. The identity of Cryptosporidium species was determined by polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) analysis, and by DNA sequence analysis of the small subunit (SSU) rRNA gene. C. parvum was subtyped using sequence analysis of the 60 kDa glycoprotein (gp60) gene. The highest infection rate of 83.3% (40/48) was seen in 2–3-week-old calves with diarrhoea, corresponding to the age at which animals died. Three Cryptosporidium species were identified, including C. parvum (n = 51), C. bovis (n = 1), and C. ryanae (n = 1). All C. parvum isolates were further identified as subtype IIdA15G1. CONCLUSIONS: Cryptosporidium parvum was likely to be most responsible for diarrhoea and death. This is the first report of a cryptosporidiosis outbreak caused by C. parvum IIdA15G1 in Chinese dairy cattle.