Hog virus cases dwindle over summer, but threat remains

The highly contagious porcine epidemic diarrhea virus, or PEDv, has hit hog farms across the country hard since it was first detected in April 2013. Since then, the disease has killed 10 percent of the nation's hog population by some estimates, primarily in the winter months.

But with fall looming, livestock farmers and veterinarians in North Carolina say they hope the measures they've put in place to stop the virus will prevent the massive die-offs they saw last winter, which resulted in millions of dollars in losses for the state's $2 billion industry.

"We’re all holding our breath to see what happens," said Dr. Tom Ray, director of livestock health programs at the North Carolina Department of Agriculture and Consumer Services. "We’ve only had one winter, and that’s been kind of a horrendous winter for us."

PEDv is classified as a coronavirus, which all share a common enemy in heat and humidity. Summer means PEDv can't spread as regularly, and that's brought the number of new cases identified nationally down to around 60 per week from a peak of about 350.

For most hogs, the virus isn't much of a problem.

For a few days, adult pigs will experience diarrhea, vomiting and fever. They may even stop eating for a day or two before recovering.

But for piglets on infected farms, these symptoms mean a mortality rate upward of 90 percent.

"It's basically just dehydration," said Timmy Thomas, owner of Thomas Farms Pork in Timberlake. "The younger pigs just don't have the body mass to ward it off."

Although his farm has been spared from PEDv so far, he's seen and heard plenty about the effects on other farms all over the state.

"When it breaks, you're pretty much guaranteed to lose 100 percent of the animals less than 4 weeks of age," Thomas said.

Able to survive for several days outside a host under the right conditions, the virus spreads quickly and easily through the consumption of infected bodily fluids (it does not affect humans). Veterinarians also consider airborne fecal matter a transmission risk.

"The tiniest pinpoint drop of the fecal material has tremendously high numbers of virus particles," Ray said.

PEDv is so contagious that it's been able to slip through the swine industry's strict biosecurity measures, which require farmers to shower and change clothes and footwear before entering and exiting barns.

"It's very much like a high-biosecurity hospital," said Dr. Barrett Slenning, director of agrosecurity and biopreparedness at North Carolina State University's College of Veterinary Medicine. "It's been very surprising to most of us that those standard methods have not kept the disease at bay."

To battle the virus, Ray said, the swine industry in the state and nationwide began re-evaluating disease prevention measures.

"When you get something like this that is able to bypass a lot of the controls that manage many other diseases, it can't help but serve as a wake-up call," Slenning said.

Because just about anything, from a worker's boot to an equipment delivery, can transmit the disease, farms had to coordinate the movement of supplies such as feed and fuel from clean to infected farms. Facilities set up truck washes and disinfectant stations. Waste lagoon inspections by the state Department of Environment and Natural Resources were pushed back to the summer.

In June, the U.S. Department of Agriculture issued a federal order requiring stricter reporting and management plans for infected farms.

Some of the measures can be costly, Ray said, but not as much as recovery from the disease.

One company told him it cost around $30,000 to clean up a facility after testing positive for the disease. He said that adds up quickly for the 1,000 herds of female swine, or sows, whose piglets would be most affected.

It may not mean financial ruin, Ray said, but infected farms that lose their young hogs are likely to lose about five weeks of their annual growth.

"If you said, 'I’m going to take a month of your salary away and let you live on 11 months of pay instead of 12,' that would really pinch you," Ray said. "Its not an insignificant thing at all."

That cost reverberates through the business.

"Seventy percent of your money is invested in that animal when he's born," Thomas said. "When you lose them, there's an awful lot of pigs needed to make up for the loss."

For the industry statewide, the economic effects of PEDv have been far-reaching.

Primary production puts hog farming in North Carolina at about $1.9 billion annually. But Slenning said the surrounding economy spurred by swine transportation, processing and retail put it closer to $10 billion to $15 billion worth of business for the country's No. 2 pork-producing state.

Given that, like the rest country, the state has lost about 10 percent of its swine herd, Slenning said it's not hard to see how deep the virus has cut.

"We've probably lost close to a billion dollars in economic activity in our state," he said.

Since the beginning of summer, veterinarians have identified fewer than 10 new PEDv cases a week in North Carolina. But there's concern among farmers, veterinarians and state officials that those low numbers won't last as the winter approaches.

"Summer months and high temperatures and humidity, which are very detrimental to the coronavirus, probably has had more to do with the decline in number than any other single factor, regardless of biosecurity and routing and placements and all that," Ray said.

Yet, along with that concern is some hope that things won't be so bad this time around.

The rapid spread of the disease means many previously infected sows pass immunity down to their piglets. Contrary to where they were when the first cases hit North Carolina in July, the state's herd is no longer a "naive population."

"We’re definitely in a better place," Ray said. "Not only were the pigs naive, but we were sort of naive – we’ve never had this virus in the country before."

Farmers also got some promising news last week, when livestock pharmaceutical giant Zoetis obtained a conditional license from the USDA for a new PEDv vaccine.

"If they're able to ramp up production and it proves itself in a farm setting to be useful in preventing disease spread, this winter will look much different," Slenning said.

While he said it's not likely to be a "silver bullet," Ray said the vaccine combined with better prevention and natural immunity may scale down the threat to a more manageable level.

"We learned a lot this year the hard way, the expensive way," Ray said. "Hopefully that’s going to help us."