Investigating the introduction of porcine epidemic diarrhea virus into an Ohio swine operation
Bowman et al. BMC Veterinary Research
Investigating the introduction of porcine epidemic diarrhea virus into an Ohio swine operation
Andrew S Bowman 0
Roger A Krogwold 2
Todd Price 1
Matt Davis 4
Steven J Moeller 3
0 The Ohio State University College of Veterinary Medicine , 1920 Coffey Road, Columbus, OH 43210 , USA
1 North Central Veterinary Service , Sycamore, OH 44882 , USA
2 USDA, APHIS, Veterinary Services , Pickerington, OH 43147 , USA
3 The Ohio State University College of Agriculture , Columbus, OH 43210 , USA
4 Hord Livestock Company , Bucyrus, OH 44820 , USA
Background: Porcine Epidemic Diarrhea virus (PEDV) is a highly transmissible coronavirus that causes a severe enteric disease that is particularly deadly for neonatal piglets. Since its introduction to the United States in 2013, PEDV has spread quickly across the country and has caused significant financial losses to pork producers. With no fully licensed vaccines currently available in the United States, prevention and control of PEDV disease is heavily reliant on biosecurity measures. Despite proven, effective biosecurity practices, multiple sites and production stages, within and across designated production flows in an Ohio swine operation broke with confirmed PEDV in January 2014, leading the producer and attending veterinarian to investigate the route of introduction. Case presentation: On January 12, 2014, several sows within a production flow were noted with signs of enteric illness. Within a few days, illness had spread to most of the sows in the facility and was confirmed by RT-PCR to be PEDV. Within a short time period, confirmed disease was present on multiple sites within and across breeding and post weaning production flows of the operation and mortality approached 100% in neonatal piglets. After an epidemiologic investigation, an outsourced, pelleted piglet diet was identified for assessment, and a bioassay, where nave piglets were fed the suspected feed pellets, was initiated to test the pellets for infectious PEDV. Conclusions: The epidemiological investigation provided strong evidence for contaminated feed as the source of the outbreak. In addition, feed pellets collected from unopened bags at the affected sites tested positive for PEDV using RT-PCR. However, the bioassay study was not able to show infectivity when feeding the suspected feed pellets to a small number of nave piglets. The results highlight the critical need for surveillance of feed and feed components to further define transmission avenues in an effort to limit the spread of PEDV throughout the U.S. swine industry.
Feed; PEDV; Swine
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Background
Porcine epidemic diarrhea virus (PEDV) is a coronavirus
of the genus Alphacoronavirus. Disease from PEDV is
characterized by vomiting, anorexia, and watery diarrhea
in swine. The virus is particularly deadly for neonatal
pigs for which malabsorption and dehydration [1-3] can
result in mortality rates approaching 80%-100% [2,4].
Disease caused by PEDV is clinically indistinguishable
from transmissible gastroenteritis virus and cannot be
diagnosed on presentation alone [4]. Because attempts at
virus isolation have only resulted in limited or temporary
success, with virus isolation rates as low as 4% [5],
diagnosticians heavily rely upon RT-PCR tests to directly
detect viral nucleic acid and diagnose PEDV.
PEDV was first identified in Belgium in 1978 and in the
1980s and 1990s, PEDV was found throughout Belgium,
England, Germany, France, the Netherlands, and Switzerland
[6]. Since the European emergence, PEDV has affected the
pork industries in Philippines, South Korea, and China [7].
In May 2013, the United States confirmed the first cases of
PEDV on farms in Iowa and Indiana [2], after which the
virus spread quickly throughout the country. While the
mode of PEDV introduction to the U.S. remains unknown,
comparison of available sequence data indicates the PEDV
strains detected in the Unites States have an ancestry linked
to PEDV strains detected in China. At the end of 2013,
sequenced U.S. strains had greater than 99.0% sequence
identity and several strains shared unique nucleotides with
a Chinese PEDV strain isolated in the Anhui Province
(AH2012) [2,3]. Unexpected genetic similarity of U.S.
PEDV strains to a bat coronavirus isolated in southeastern
China may provide evidence for the role of cross-species
transmission in the development of emergent strains that
spread to the United States [3].
Transmission of PEDV occurs via the fecal-oral route
[7] and fecal contamination of fomites may play a role in
the introduction of the virus to swine. An investigation
of 575 livestock trailers at 6 harvest facilities in the
United States showed that all truck drivers stepped into
the harvest facility at least once, and the proportion of
PEDV contaminated trailers increased from 6.6% before
unloading to 9.2% after unloading [8]. These data
indicate that contaminated transport vehicles and personnel
could be associated wit (...truncated)