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Is PEDV exposure a tool for elimination?

Article-Is PEDV exposure a tool for elimination?

National Pork Board Acclimating gilts to stalls
Controlled exposure of gilts before they enter a sow barn in a high dense area sounded like an ideal solution at first.

Since porcine epidemic diarrhea virus was first introduced in 2014 in Manitoba, the province's pork production network has taken an aggressive approach to eradicate the virus.

"We've done it over 270 times as an industry, more than 90 times in the sow barns," says Karine Talbot, DVM, HyLife Ltd. "We're good at eradicating PEDV."

From farrow to finish, PEDV is managed throughout the province's production chain, with some barns having successfully eradicated PEDV three to four times. After cases have been eradicated, on-going surveillance continues with daily testing at the two federally inspected slaughter plants and regular inspection at assembly yards and provincial slaughter plants.

But PEDV keeps coming back.

While the outbreaks have continued on a two-year cycle and remained localized to the southeast corner of Manitobaa pig dense area for the provincethe seasonality of the breaks has changed more recently. During the 2017 and 2019 outbreaks, cases generally started showing up in late April, with more barns breaking in May and June. In 2021, the province made it through the spring and summer with no cases of PEDV, until Oct. 25 when a sow barn near Blumenort tested positive.

From the end of 2021 through 2022, more than 100,000 sows were infected with the virus. The two-year outbreak included 34 sow barns, 23 nurseries, 61 finishers and 10 farrow-to-finish and nursery-finishing sites.

"It's very complex, it's a terrible disease and it has changed our lives," Talbot says. "It may seem like the end of the world, but it's very localized in our province," Talbot says.

In Manitoba, a case of PEDV is not managed as a single, individual producer's decision, but as a group approach, she says. It is understood that the plan chosen will impact not only the producers dealing with PEDV, but also producers in the high-risk area that have kept the virus out, as well as producers throughout the entire province.

In early 2022, a Future Management of PED Working Group was created and included Manitoba Pork Board representatives, veterinarians, integrators, independent producers and the office of the Chief Veterinarian (provincial government). The group's goal was to develop a PEDV management strategy for Manitoba.

One of the first questions the group tackled was: Can gilts be exposed to create immunity and prevent sow barns from re-breaking every two years?

The group collaborated with the Western College of Veterinary Medicine in Saskatchewan to assess the efficacy of vaccines, biosecurity measures, feedback, PEDV shedding, financial impact and various control strategies for the virus.

While a controlled exposure of gilts before they entered a sow barn in the high dense area sounded like an ideal solution at first, Talbot says the group soon realized the logistics to complete the process would impact all producers:

  1. To provide immunized replacement animals to the infected sow barns in the southeast area, 50,000 gilts per year would need to be exposed to the virus. These gilts represent multiple production systems and independent producers, each with their own genetics and source of gilts. On top of those production considerations, multiple barns would need to be dedicated to house the gilts and expose live PEDV.
  2. Having acclimatized gilts does not guarantee that barns won't be infected again. If barns do break again, the viremic piglets will just be placed in nurseries, exposing more animals to PEDV, with the virus cycle continuing on.
  3. The barns would also need to be isolated enough to not put any other barn at risk for PEDV while constantly exposing naïve gilts. As Talbot points out, exposure wouldn't just take one or two times, but multiple contact points. Continuous biocontainment measures would need to be in place for deadstock removal, feed delivery, livestock movements, people and traffic. Where could one safely expose that many gilts without leaking the virus to other farms?

After reviewing the studies and discussing the pros and cons, the Manitoba PEDV working group concluded that PEDV exposure was not a tool for elimination for the province.

"We decided we just cannot take the benefit of one producer or a few for the rest of our producers," Talbot says. "So, we're going to stick together and keep working toward full eradiation of PEDV."

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