1. Introduction
Neonatal calf diarrhea caused by intestinal pathogens including
bacteria, viruses and parasites is a leading cause of morbidity and
mortality in pre-weaned calves (Gomez &
Weese, 2017). Rotavirus, coronavirus, Escherichia coli , andCryptosporidium spp. are considered the most important causes for
calf diarrhea (Meganck, Hoflack, &
Opsomer, 2014). Synergistic infections of these pathogens were often
identified during outbreaks of diarrhea in calves
(Foster & Smith, 2009;
Gomez & Weese, 2017). Among them,Cryptosporidium spp. and rotavirus are the most frequently
observed pathogens in fecal specimens from neonatal calves worldwide
(Mohamed, Mansour, El-Araby, Mor, &
Goyal, 2017; Thomson et al., 2017). In
addition, moderate-to-severe diarrhea caused by Cryptosporidiumspp. is of the leading causes for morbidity and mortality in young
children in developing countries (Kotloff
et al., 2013).
Cryptosporidium spp. are especially common in dairy calves. The
cumulative infection rate of Cryptosporidium spp. in pre-weaned
dairy calves in the United States is 100.0%
(Santin, Trout, & Fayer, 2008;
Xiao & Herd, 1994). In China, the
average infection rate of Cryptosporidium spp. in dairy calves
with diarrhea was 45.8%, much higher than that in cattle overall
(14.5%) (Wang, Zhao, Gong, & Zhang,
2017). Numerous cryptosporidiosis outbreaks have been reported in
neonatal calves in the United States, European countries, Australia,
India, and China, causing serious harms to the dairy industry
(Brar et al., 2017;
Cui et al., 2014;
Izzo et al., 2011;
Li et al., 2019;
Ouakli et al., 2018;
Randhawa, Randhawa, Zahid, Singla, &
Juyal, 2012).
Among the over 40 established Cryptosporidium species
(Feng, Ryan, & Xiao, 2018), C.
parvum , C. bovis , C. ryanae and C. andersoni are
commonly found in cattle (Ryan, Fayer, &
Xiao, 2014). Among the latter, C. parvum is the only
major pathogenic and zoonotic species
(Thomson et al., 2017). The
distribution of Cryptosporidium spp. in cattle in China, however,
is very different from other countries, with C. bovis being the
most common species in pre-weaned calves rather than C. parvumelsewhere (Feng & Xiao, 2017). In
addition, subtyping of C. parvum based on sequence analysis of
the 60 kDa glycoprotein (gp60 ) gene indicates that calves in
China are exclusively infected with IId subtypes
(Feng & Xiao, 2017). Elsewhere, IIa
subtypes are mostly identified in calves, while IId subtypes are usually
seen in lambs and goat kids (Xiao, 2010).
Thus far, almost all investigations of cryptosporidiosis outbreaks in
humans and calves caused by C. parvum have focused on its IIa
subtype family in industrialized nations. The clinical importance of the
IId subtype family of C. parvum is less clear. Two recent
outbreaks, however, have been reported in dairy calves in China,
responsible for substantial mortality (Cui
et al., 2014; Li et al., 2019). They
were caused by IIdA15G1 and IIdA19G1 subtypes, two dominant C.
parvum subtypes in calves and other animals in China
(Feng & Xiao, 2017).
Here, we report the results of an investigation of a cryptosporidiosis
outbreak in neonatal calves on a large cattle farm in Hebei Province,
China caused by another IId subtype of C. parvum . Approximately
20% of neonatal calves on the farm died of watery diarrhea during the
outbreak period.