It’s shaping up to be another bad year for PEDv in the province’s pork sector.
In fact the province says it could easily be on par with 2017, the province’s worst year.
On June 18, Dr. Glen Duizer of Manitoba’s Chief Veterinary Office (CVO) said 2019 cases were comparable to the same point in time in 2017. There had been 41 reported cases by the end of June 2017, rising to 80 — eight times more than the previous three years combined — by the end of 2017.
There are now over 40 cases this year, as of June 24, according to Manitoba Pork. The latest available number from the province was 36 cases, as of June 18.
Manitoba saw a relative lull last year in PEDv following the 2017 outbreak. Only 16 cases were confirmed in 2018.
Why it matters: Before 2017, Manitoba saw five or fewer cases of porcine epidemic diarrhea virus (PEDv), a disease that can kill 80 to 100 per cent of piglets less than a week old. Two years ago, those annual cases jumped to 80, and this year might be shaping up much the same.
Anxiety has risen with news that the virus has crossed west of the Red River. Four cases had been reported in south-central Manitoba as of June 21.
Two cases were also confirmed west of the Red River in 2017, both were later linked to direct animal movement from an infected barn in the east. Western cases this year did not have such a link, a fact that the Manitoba Pork Council has noted with concern.
“It leads us to question how it would have got there,” said Jenelle Hamblin, Manitoba Pork Council manager of swine health programs. “This virus is quite elusive and we haven’t been able to pinpoint a lot as to how it’s moving.”
Producers did try and reduce day-to-day transport following the 2017 outbreak, she said, although that risk is difficult to eliminate, since the pork production system requires regular movement.
Residual immunity has somewhat buffered piglet loss compared to 2017, Duizer said, although losses in naive barns have been severe. About 60 per cent of infected barns this year were previously infected, the province reports.
“It is by no means protective for the entire herd,” he said. “But it does seem to limit the impact a certain degree, and that obviously wanes over time. The problem with the residual immunity is that it’s not preventive of the disease, it just seems to limit the impact, especially in some of the older piglets.”
Reinfection is not necessarily a sign of biosecurity gaps, he added. Manure from 2017 remains a possible chink in a barn’s defence, even after the virus has disappeared from the herd. The province estimates that residual risk from manure might last at least two years, although the exact window is unknown.
“There certainly could be risk factors that they maybe didn’t fully address last time around, but in many cases you’re also looking at larger farms in swine-dense areas and those in themselves are risk factors,” he said.
Both HyLife Foods and Maple Leaf Foods are currently battling the virus.
Eight HyLife Foods barns had tested positive for PEDv as of June 19, company founder Claude Vielfaure said.
“Since (the) first PED showed up in Manitoba a few years ago, we’ve obviously looked very, very closely to our biosecurity controls and tried to improve them over the years and this virus is a bit of a mystery on how it spreads,” he said. “It’s a tough one.”
The company is looking for further improvements and extra biosecurity measures, he said.
The company has acquired additional hogs from other barns in Manitoba and Saskatchewan due to potential loss.
Maple Leaf Foods did not reveal how many of its barns were infected, but did confirm the virus’s presence in its facilities.
“All major systems and some independent farms have had cases of the virus including Maple Leaf Foods,” the company said over email. “All producers in Manitoba are following stringent biosecurity protocols. However, weather and windy conditions driving aerosol spread via dust is definitely a factor in this year’s PEDv cases.”
Long shadow of 2017
The CVO believes this year’s outbreak is still spillover from 2017, rather than a new source of infection from out of province, Duizer said. Hamblin pointed to sequencing work being done to verify current PEDv strains and confirm where the continued infections are coming from.
Veterinarians and the sector as a whole hope to get a better idea of how risk factors from 2017 might come into play today, she said, including things like area spread, manure application, and how far the virus might move without human help.
The virus has been dismayingly tenacious, Duizer noted, and 2017 carry-over has already proven more vigorous than many assumed at the end of the outbreak two years ago.
“It has surprised us and I think it’s surprised not just us with the CVO. It’s surprised the herd veterinarians. It’s surprised the sector itself,” he said. “When we look particularly at the southeast, we didn’t expect the impacts to be lasting this long.”
The CVO has little idea of how long Manitoba’s pork sector might be fighting the aftermath 2017, although Duizer says his office is devoting much effort to answer that question.
“Right now, what we can say is that it’s definitely more than a couple of years, that’s obvious if we look back at 2017,” he said. “How long that’s going to be… do I think it’s going to be a decade? No. But do I think that it’s going to be a longer-term control and eradication strategy that’s going to have to deal with multifactorial components across, in particular, the swine-dense area in southeastern Manitoba? Yes.”