Editor's note: The following article was originally published in the March 2015 issue of PORK Network.
Like a vicious invader, Porcine Epidemic Diarrhea virus (PEDv) slipped silently through the borders nearly two years ago, swiftly infecting millions of pigs on pork operations of all sizes on its journey across the country. The American Association of Swine Veterinarians (AASV) first identified the disease in May 2013, and though it has been a long 21 months since the first reports of the outbreak surfaced, today the industry knows more and is doing more to keep PEDv off farms and away from pigs.
At the 2015 Iowa Pork Congress in Des Moines, Iowa, a panel of experts presented PEDv updates, insights and encouragement to an industry currently holding its collective breath to see if enhanced biosecurity and surveillance measures enforced over the last year will be successful or futile.
“It didn’t need to be here”
Matt Anderson, DVM, with Suidae Health and Production, was president of the AASV when PEDv was first detected in U.S. hog herds. He admitted the disease wasn’t always on the organization’s disease radar. “At that time, we were focused on African Swine Fever, which had begun to show up in Europe,” he explains. “We were more concerned about Classical Swine Fever and Pseudorabies – diseases we had defeated here but were still present in other countries.”
Ready or not, PEDv did make its way onto U.S. soil, something Anderson strongly believes didn’t need to happen. “Somebody didn’t walk through an airport with the virus on the sole of their shoes, going from farm to farm, and spreading it from there,” says Anderson. “This, in my mind, was a point-source origin virus. Something we did that affected multiple disconnected herds in the same time frame made those herds positive. It’s worth talking about time and time again. We don’t need to have PED in this country.”
With some economists attributing as many as 8 million pig losses to the outbreak, Anderson suggests it could have been worse, especially considering 25 percent of pork produced domestically is exported. “I would like us to keep in mind we could just has easily be talking about Foot and Mouth Disease, Classical Swine Fever or another foreign animal disease that would have shut down our international borders and closed those export markets,” Anderson points out. “Anything that forces 25 percent of our product back onto the domestic market should concern us very deeply.”
One of the problems in battling PEDv lies in its ability to spread infection with very few virus particles. Darin Madson, DVM, PhD, DACVP, College of Veterinary Medicine, Iowa State University, elaborated on this viral nature. “It takes very few particles to cause infection. In essence, one to two virus particles is enough to infect a day-old piglet,” says Madson.
Producers, veterinarians and researchers quickly realized the need to ramp up biosecurity. These efforts required plans that redefined the level and methods of disinfecting both trailers and rooms. “Clean isn’t always clean enough,” Anderson explains. “Last year, I probably would have told you at this point in time that our biosecurity was pretty good, but it may have been relative to 20 years earlier. It wasn’t good compared to today. I hope a year from now we’re better off than we are today.”
Traditional means of disinfecting trailers and rooms still allow enough virus to remain. Heating trailers and rooms to 160° F. for 10 minutes, 115-120° F. for 24 hours or 68° F. for one week appears to provide enough heat to eliminate the risk of spreading PEDv (see article on page 12).
Anderson stresses that the key to PEDv isn’t just to eliminate it from hog herds – it’s to avoid it altogether. “Keep it out when you can, eliminate it if you must but be generally unwilling to live with ongoing infection,” he says.
More About Immunity
PEDv vaccines have remained a hot topic among producers and veterinarians. At this time, two companies have been granted conditional licenses from the USDA – Zoetis and Harrisvaccines. See the side bar on page 10 for field experiences with a vaccine, as well as research funding that will increase knowledge on PEDv. While these first generation vaccines offer some protection, both Anderson and Madson point to difficulties in using vaccines to stimulate immunity in piglets, where the vaccine effects would be maximized.
“It’s going to be difficult to try to get the antibodies where they need to be. You really don’t need colostral immunity in the incidence of PEDv,” says Madson. “You need lactogenic immunity. You need those antibodies to be in the milk, to be binding to the virus within the intestines before it infects the cell. That’s where the immunity of this virus takes place.”
It’s undeniable that the industry has made impressive strides in on-farm biosecurity and surveillance plans. These efforts are something Anderson praises, giving “kudos” to the industry as a whole.
“Never in my experience have I seen an industry come together cooperatively as quickly as in this case,” Anderson states. “We are a competitive industry, but competition in this case went out the window. Companies were helping each other out; farm [owners and managers] were helping each other. I was really proud to be part of the industry during that period in time. It was full of challenges, but all of the producers and everyone who supports producers really stepped up. That allowed us to make progress.”
Even so, it’s too early to relax. The next several months will be critical.
Anderson cautions, “The number of confirmed cases may be lower at this point in the year compared to 2014, but it’s not dramatically lower than this same point in time last year. I think before we pat ourselves on the back too much, we have to see what the next 2-3 months brings and really remain vigilant.”