AMES - It's winter, and with 2014 just around the corner the number of reported porcine epidemic diarrhea virus cases continue climbing.
Nebraska reporting officials are the latest to add the Cornhusker state to the ranks of those with three confirmed cases.
Dr. Rodney Baker, an Iowa State University diagnostic veterinarian, who is among those monitoring PEDV's spread, said that as of the latest Dec. 11 information available there are now 4,694 biological samples testing positive for PEDV in 20 states..
The report shows North Carolina is at the top of the list in the number of cases with 1,307, followed by Oklahoma with 939 cases and Iowa with a total of 844 cases leading the 20 states now showing the virus.
"There's a lot going on right now at all levels of pork production," Baker. "We've only recently just learned that the virus has been marching through Carroll County in northwest Iowa with the count showing five to six sow farms.
"It's a nasty situation all the way around."
National reports, Baker said, don't always reflect the number of farms with the virus in that some of the numbers may come from the same farm and same systems, but at different stages of the virus.
Some younger pigs are showing signs of surviving the virus, rather than dying in huge numbers as when the outbreak started last spring in the U.S.
"In larger production systems we're not seeing PEDV come and go as we expected earlier," Baker said.
He said he thinks the problem is a 30 percent chronic situation in that piglets that shed the virus become older pigs with immunity, affording some protection for the young following them.
The onslaught of winter weather is not expected to bring any drop in reported cases, Baker added, but rather prompting increases in reported cases of the virus.
"The virus is not environmentally stable and actually likes the cold," he said. "Clouds and winds make this time a good one for (PEDV)."
He compared it to similar situations with the transmissible gastroenteritis virus.
"Winter conditions can also make it very difficult to eliminate the virus in a facility," he said, "due to difficulty in cleaning outdoor facilities. This then allows the virus to freeze and be non-active for a time for as long as three fall cycles."
PEDV is also able to adapt gene modifications during this period allowing for development of variation resistance, he said.
Diagnosis research into the virus continues, Baker said, with all the answers "a long way down the road" as to the cause and PEDV's appearance in the United States.
"It appears to us that the arrival of PEDV (first confirmed in the United States on May 17) is the result of an accident resulting from feed ingredients coming from China," Baker said. "This means there is obviously a portal in our (animal health) defense system we need to watch, and it can be a scary one."
As to whether the U.S. outbreak has any possible links to an act of intended global terrorism, Dr. Baker said it appears otherwise. He does not see it as a "virus of choice" for such a use in contrast to the possible disruptions caused by fibromuscular dysplasia, or foot and mouth disease, which can affect all cloven-hoofed animals.
As a result of the disease's global outbreaks in previous years, FMD is now included on the international list of diseases.
This, he added, has been due to FMD's potential impact on free trade and export of livestock meat exports, including pork, among exports adding significantly to the U.S. agricultural economy.