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Cold, wet weather increases risk of PED virus

Vigilant biosecurity practices are important as seasons change

Hog producers are warned to be particularly vigilant about biosecurity practices this fall because the porcine epidemic diarrhea virus (PEDv) is more likely to survive in cold, wet weather.

“We expect to see more cases in the fall,” said Mark Fynn, animal care specialist at the Manitoba Pork Council.

Manitoba’s Chief Veterinary Officer (CVO) had recently confirmed two new cases of PEDv in the province, bringing the total to four. Both were discovered on sow farms in the southeast. The virus, though not dangerous to human beings, is often lethal for pigs, particularly piglets, and devastating to production and operations in the pork industry.

A spokesperson for Manitoba Agriculture, Food and Rural Development said in an emailed statement the department could not yet confirm the source because “the epidemiological investigation is ongoing.”

Manitoba Pork Council released a statement earlier reminding producers to follow the proper biosecurity measures, such as wearing disposable boot covers when walking around high-risk sites and properly washing trucks and equipment before re-entering the farm.

“Although it is disheartening to see another case arise, we should use this as a lesson learned and elevate our biosecurity practices, especially with cold, wet weather looming,” Manitoba Pork said. “As we know, the risk of the virus spreading increases exponentially in colder seasons.”

Symptoms of PED in older animals such as sows are generally limited to “loose feces,” the CVO said.

Fynn said determining the causes of single cases is difficult. “It’s hard to pinpoint those factors having an effect on one case because it’s rather anecdotal.”

He looks to areas with higher occurrences of the virus, such as the United States and Ontario, for seasonal patterns.

This year there were 63 cases of PEDv in Ontario, according to Ontario’s Ministry of Agriculture, Food and Rural Affairs website. Fifty-eight of those cases were spotted near the end of January until the end of April. Only five cases were reported during the summer.

The U.S. has also seen the virus incident rates decrease in the summer. The percentage of PED-positive environmental samples more than doubled between November and May (an average of 24.19 per cent), compared to the summer — between June and September (an average of 9.5 per cent).

“In the summer months, temperatures denature the virus. Dried conditions as well don’t favour the virus surviving,” said Fynn. “The probability increases exponentially when we’re dealing with colder months.”

Research in 2013 by Sagar Goyal, at the University of Minnesota, explored the PEDv survivability in manure and confirmed it survived longer in colder conditions.

He tested samples of slurry containing PEDv stored at 25 C, 4 C and -20 C and at different levels of humidity. The virus lived for 14 days at room temperature. However, PEDv in the samples stored at the colder temperatures survived 28 days, which was the duration of the study.

Goyal also found the virus lived longer in wet conditions — it survived only a week in dry feed, but in wet feed, it survived for the entire 28 days of the study.

Andrew Dickson, general manager of the Manitoba Pork Council, said the latest case and cooler weather are both good reasons to be more diligent about biosecurity.

“This is the time producers have to be more vigilant,” he said.

Producers are reminded to follow proper procedures as they clean out manure storage facilities and spread their fields. This means more work, but ultimately the precaution is worth it.

“If producers follow the standards we developed four years ago they should be well protected,” said Dickson.

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