WASHINGTON — A potentially-costly virus in the U.S. hog herd
has veterinarians and those in the U.S. hog industry doing some detective work.
“I believe it’s truly a new introduction,” said Dr. Joe
Connor of Carthage Veterinary Service in Carthage, Ill.
PEDV, Porcine Epidemic Diarrhea Virus, has been confirmed,
as of May 31, in four states — Illinois, Indiana, Iowa and Colorado.
According to the U.S. Department of Agriculture’s Animal
Plant Health Inspection Service, a case of PEDV was confirmed in a herd in Iowa
on May 16 by the National Veterinary Services Laboratories in Ames, Iowa.
“It is very similar to (Transmissible Gastroenteritis) with
even a higher mortality and affecting the 17-day, 18-day, 19-day suckling pigs
at a higher mortality. It is most active in pigs from birth to 21 days of age,”
“Of the pigs in a farrowing house today, we would expect to
lose 80 percent, a three-week loss at 80 percent,” he said. “As soon as the sow
herd develops immunity, about 14 days after exposure, then mortality starts to
decline because the pigs are protected through the sow’s milk. They are not
fully protected until 21 days.
“You have a window in there of three and a half to five
weeks when you have high mortality. The mortality in the sow herd and in the
grow-finish population is very low.”
Connor said that because the symptoms so closely mimic TGE,
it’s possible that PEDV could initially be identified as TGE.
“These pigs are best considered to have TGE with extreme
diarrhea, vomiting and huddling and with mortality in 24 to 48 hours. Then we
will see diarrhea very quickly in the sow unit,” he said.
PEDV is not zoonotic — that is, it cannot be transmitted
from swine to humans — and it does not pose a food safety concern. PEDV is not a
listed disease of the World Organization for Animal Health, and there are no
interstate trade restrictions regarding PEDV in the U.S.
Connor said the disease has not been identified in the U.S.
herd prior to the May 16 confirmation in Iowa.
“It is present in other parts of the world. It was first
seen in England in 1971 and then in the late 1970s, early 1980s in Asia and it
is very active in the Asian countries today. This particular strain does match
up 99.45 percent similar to the Asian China strain,” he said.
Connor said that a number of surveys currently are ongoing
to try to determine the source of the introduction.
He said he is confident that swine health experts did not
miss outbreaks of the disease masked as TGE. Testing will include serological
tests on fecal samples of pigs in the grow sector.
“We will have a serological test for PEDV projected to be in
about three to four weeks so we will be able to go back and look. We’ve asked
our producers and vets to bank samples from pigs in the growing population,” he
Other surveys are looking at risk factors to find ways to
control transmission of the virus.
“There are a number of epidemiological surveys being done.
They’re designed to look at all the risk factors,” Connor said.
He said the same methods producers use to eliminate TGE also
can work to eliminate PEDV.
“There is no treatment because it’s a virus and no vaccine
in the United States. It would be eliminated with the same protocol as TGE which
is, in breed to wean, expose all animals to the virus, including three months’
of replacement gilts. Generally, that’s been quite effective and would appear to
be effective here,” he said.
“In wean to finish, it’s a matter of emptying all the
buildings, power-washing them and being sure that they are clean. That will
break it. If the next population is negative, that population will stay negative
with normal biosecurity procedures.”
Connor stressed that reviewing and intensifying biosecurity,
including transportation of animals to and from facilities, also can help
prevent the spread of the virus.
“Producers should manage those high risk areas and review
their biosecurity,” he said.
Connor said that veterinarians and producers have been
active in trying to identify herds that have contracted the virus.
“The veterinarians have been very, very active from that
first case. Suspect breaks of diarrhea that appear to be TGE-like are being
followed up with good producer interaction. We have three labs that can run
samples, K-State, Iowa State and Minnesota State. The turnaround time is 24
hours on those samples, and there is extensive sample collection going on and
processing of those samples. From that, we will get the number of true cases,
and we’ll be able then to look at what the risk factors might have been in those
cases,” he said.