Cryptosporidiosis outbreak caused by Cryptosporidium parvum subtype
IIdA20G1 in neonatal calves
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 presented watery diarrhea and
over 40 died. To investigate the cause of the outbreak, 179 and 223
fecal specimens were collected during and after the diarrhea outbreak
from the farm, including 40 and 56 from neonatal calves, respectively.
Among them, 18 fecal specimens from ill calves during the peak of the
outbreak were analyzed for four common enteric pathogens using enzymatic
immunoassay (EIA), 75 additional specimens from neonatal calves were
tested for rotavirus by EIA, and all specimens were analyzed for
Cryptosporidium spp. using PCR and sequencing techniques. Of the initial
18 specimens 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 (21.6% or 8/37) and after (18.4% or 7/38) the outbreak. In
contrast, the prevalence of C. parvum was significantly higher during
the outbreak (60.0%, 24/40) than after the outbreak (30.4%, 17/56). C.
parvum infection was associated with the occurrence of watery diarrhea
in neonatal calves (odds ratio = 11.19), while no association was
observed between C. bovis infection and diarrhea. All C. parvum isolates
were identified as subtype IIdA20G1. Older animals were infected with C.
bovis, C. ryanae, C. occultus, and C. andersoni. 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 preventing the
dissemination of C. parvum in China.