Relentless PED virus could return to hog barns at any time

An outbreak appears to be contained but incredibly hardy PEDv could reappear at any moment

We’ve got all of Saskatchewan between us — but that’s not enough to shield Alberta from the threat of a deadly pig virus that has swept across Manitoba.

The virus that causes porcine epidemic diarrhea virus (PEDv) is proving to be a challenge unlike any other — an incredibly hardy infectious agent able to travel vast distances and then infect barns seemingly out of the blue.

Julia Keenliside.
photo: Supplied

“You have to remain vigilant because of the huge amount of PEDv in Manitoba,” said Dr. Julia Keenliside, veterinary epidemiologist with Alberta Agriculture and Forestry. “There are probably over 60 cases in Manitoba now, and a huge amount of traffic that goes between Alberta and Manitoba in terms of trucks, and feed and people.”

Despite a massive biosecurity effort to keep PEDv out of Alberta, the province saw four cases in rapid succession at the start of the year.

The four affected farms — all medium-size farrow-to-finish operations — appear to have successfully contained the virus. But the threat of future outbreaks remains high because the virus’s ability to survive seems like something out of a science fiction movie.

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Officials in Manitoba (who have seen, as of Aug. 27, 64 cases this year and 175 since 2014) suspect some barns might even have been infected when PEDv hitched a ride on dust.

“We can find genetic viral material in dust inside the barns, but whether it’s viable or not is another question, and we haven’t been able to answer that definitively,” Andrew Dickson, Manitoba Pork Council’s general manager, told the Manitoba Co-operator last month.

When PEDv first showed up in the U.S. (where it’s killed millions of piglets) in 2013, the primary focus in preventing its spread in Canada was on transport trucks and the places they visit.

Ensuring transport trucks are properly washed or disinfected remains a top priority but officials here believe that wasn’t how the virus arrived in Alberta.

“We found no evidence that it was moving on vehicle transport or assembly yards or abattoirs in Alberta,” said Keenliside. “The virus is so infectious — it takes so little to cause disease and it survives so well when it is frozen. This time the virus used other methods to get into Alberta. Hog transport was not one of them.”

That finding shifted the focus to the next most likely culprit — investigators suspect feed trucks coming from Manitoba and Iowa may have spread PEDv into Alberta.

“They are delivering feed ingredients to the feed mill, the truck has come from an area where they have the disease, and in many cases, the door to the barn is right across from the door to the feed mill,” said Keenliside.

Since the feed mill and the barn are often so close, people don’t change boots or coveralls between the two buildings.

“If you’re getting trucks onto your farm that are coming from places where there is PEDv, you have to enforce biosecurity and have people change boots and coveralls — all the time, no exceptions,” said Keenliside.

Producers need to think about where their feed ingredients are coming from, she added.

“We looked at all the feed ingredients that came into these (four infected) farms and we found they came from many different countries and regions, many of which had PEDv,” she said.

Every producer should sit down with their vet and critically review all of the transportation, people and equipment movement on and off their farm, and look at connections where PEDv could spread, she said.

Hard to kill

The virus that causes PED (which is not harmful to humans but usually fatal for piglets) will eventually die without a host that allows it to multiply. But it can also survive a long time in the environment, particularly ones that are cool and damp — and infected animals shed a lot of the virus in their feces.

That’s prompted a new line of inquiry by researchers from Manitoba, Alberta and the Vaccine and Infectious Disease Organization at the University of Saskatchewan.

“We’re going to take samples from the lagoons of our Alberta affected farms, plus the lagoons of some of the Manitoba affected farms,” said Keenliside. “We’re going to do a bioassay in their secure research unit, where we will expose newborn piglets to manure from the lagoons of these farms to see whether or not it is truly still infective.”

And outside sources of contamination aren’t the only threat — infected hog farms that have gone through the extensive, and expensive, process of decontamination aren’t out of the woods, either.

After a barn is infected, veterinarians, epidemiologists, and others involved in the investigation will keep cleaning and testing to ensure the virus doesn’t stay around. The team makes sure all animals are exposed and infected right away, so they develop a strong immunity.

Unfortunately, this immunity lasts less than a year.

“When they’re all immune, they all get over the virus and they stop shedding and theoretically the virus stops being produced by the environment and the disease will go away,” said Keenliside.

But in some cases, the virus lingers somewhere, only to re-emerge and infect baby or newly weaned pigs and then circulate again.

“Typically, what happens is the sows have very good immunity and that protects the nursing piglets while they are nursing,” she said. “Once they are weaned and put in the nursery, they are not getting milk from the sow any more. So if they are exposed to a little bit of the virus at the time, they can become infected and we sometimes get the virus cycling through the nursery.”

Older nursery pigs may not die from the disease, but will display signs of bad diarrhea. But the piglets of younger gilts, which don’t have immunity, may not be protected if the live virus is still present.

“That’s why we require farms to test before we give them a presumptive negative status. By looking at them, you can’t tell it’s really gone,” she said.

To be on the safe side, all the animals on the four infected Alberta farms that had the virus, have been marketed and cleaned out because these are the animals that could potentially shed longer term, she said.

An ongoing threat

The four Alberta operations (which each had 300 to 400 sows) are all on track to achieving presumptive negative status.

“The first farm opted to depopulate, clean out and repopulate,” said Keenliside, adding the other three decided to keep their animals and instead eliminate the virus through cleaning, disinfection and management.

The provincial team is following a testing protocol that is a combination of what Manitoba and Ontario require to get herds to presumptive negative. Both provinces are testing all the pigs in the barn twice in a three-week period.

“If both times, everything comes back negative, then they are presumptive negative, which means that the barn and the pigs are negative,” she said. “But we can’t determine where the manure is infective or not, and that is the hard part. If you test pits in the lagoon, they could be positive for a year or two afterwards, according to Manitoba and Ontario.

“If we find out that the manure from their lagoons and pits is no longer infective, then they will be truly negative.”

She urged producers to call their veterinarians if they see any unusual diarrhea in their herd. The symptoms are easy to miss in sows and suckling pigs.

“Every farm has to have their own biosecurity plan and identify their own risk factors,” she said.

Having a biosecurity plan can also help prevent classical swine fever and African swine fever. This message doesn’t just apply to commercial pigs, but to people with outdoor raised pigs, natural pigs and organic pigs.

“Even a small producer with just a few pigs should look at their biosecurity, employ a veterinarian and get a biosecurity plan,” said Keenliside.

And everyone raising pigs in the province needs to view the four Alberta cases as “a warning shot.”

“It made its way to Alberta this year,” she said. “There’s definitely a risk that it could make its way back to Alberta next year because this is the most PEDv we’ve ever seen in Manitoba.”

About the author

Reporter

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, she has also published two collections of poetry and a biography about a Sikh civil rights activist. Her freelance work has appeared in numerous publications across Canada.

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