Porcine epidemic diarrhea virus (PEDv) is a relatively new but growing concern for pork producers. The disease was first recognized in England in 1971, subsequently appearing in the Middle East and several European countries. It was confirmed in the U.S. in May 2013. Today, 25 states have confirmed cases of PEDv.
Like transmissible gastroenteritis (TGE), PEDv is a coronavirus, and clinical signs for the two diseases are similar. "It spreads rapidly through a population," said Dr. Paul Sundberg, a veterinarian and vice president of the National Pork Board. "It will be an epidemic outbreak in a barn--all of a sudden, every pig will get it. It spreads quickly from one place to another. The clinical presentation is a little different from TGE, but the outcome is the same."
Sundberg said that from the start, research has been focused on learning about the disease in order to help producers manage and prevent it, as well as develop appropriate biosecurity and biocontainment procedures. "The first thing we learned about PEDv back in May is that we didn't know enough about PEDv," he said. "We quickly had to fund research to tell us the very basic things about this virus. There's a lot of information from Europe and China, but it doesn't apply to U.S. production."
On day one in a PEDv-infected farrowing barn, there are few or no clinical signs, but pigs become sick between one and three days following exposure. Sundberg explained that the virus attacks the pig's intestinal lining, causing dehydration and scours. "Just like TGE, pigs that are still suckling on the sow will probably have up to 100 percent mortality," he said. "It's a very devastating disease." Infected pigs can shed the virus for as long as 21 days, and possibly longer. Sundberg noted that the entire herd doesn't have to be shedding the virus; an individual pig that's shedding can cause problems.
In older pigs, clinical signs are subtler, and close observation is necessary to detect signs of illness. In finishers and sows, animals may be lethargic and off feed for a few days without showing further signs. The morbidity rate in older animals is high, but mortality is lower, and older pigs have a better chance for recovery.
"It looks like transportation is the primary way this virus moves from one farm to another, not pig to pig," noted Sundberg. "Anything that can move manure--including people, animals, trucks, material or equipment that can be contaminated with manure--spreads the disease." The disease is spread through fecal/oral contamination--from the manure of one pig to the mouth of another. It is not spread via aerosol transmission from one pig to another, but could potentially be moved by wind if the virus is in dried manure. At this time, there is no commercially available vaccine for PEDv, but Sundberg said pharmaceutical companies are working on a vaccine that may be available this summer.
For now, the best management tool for PEDv is tight biosecurity. For pig producers who suspect PEDv, Sundberg said the first step is to contact a qualified veterinarian to make an accurate diagnosis. "There's no way to determine if it's TGE, PEDv or something else," said Sundberg. "If you have off-feed pigs that scour for even a day or two, get a veterinarian to check them. The best way for us to understand this disease is to do everything we can to track it, know where the infections are and [know] what's happening. We have to have veterinary involvement and diagnostic lab involvement. If a positive PEDv test comes up, it's part of a good neighbor policy to make sure that everyone in the neighborhood knows what's going on."
Some farmers who have small herds and farrow only once or twice a year are considering purposely exposing pigs to the virus as a means to achieve immunity. "That may be a way to approach it, but there are considerations," said Sundberg, emphasizing the importance of involving a veterinarian in such a decision. "You might be bringing a virus into a location that could cause further infections in the region."
For those anticipating spring shows and sales, tight biosecurity is even more critical. "The most effective biosecurity for PEDv is keeping pigs away from other pigs," said Sundberg. "That's the most effective way to keep this virus from moving. That said, there are shows, weigh-ins and places where pigs will be collecting. That's why we developed recommendations for exhibitors, weigh-ins and exhibit organizers. When you go to a weigh-in, a show or anywhere else pigs are congregating, ask questions, be aware and be protected. Isolate any pigs that come back and watch for clinical signs. Plan to do chores from youngest to oldest pigs. The last contact should be any pigs that are in isolation--that way you won't track anything from the isolation pigs to others. Keep pigs in isolation for 30 days, get your veterinarian involved to monitor and test any pigs that scour, and test prior to adding isolated pigs to the home herd." Other biosecurity measures include changing clothing (including footwear and outerwear) prior to working with pigs already on the farm and making sure that your pigs don't have contact with any manure from other farms.
Farms that raise pigs outside and farrow on dirt or other organic surfaces face more challenges when it comes to disinfection. "The virus doesn't survive well in dry conditions and in sunlight, so that will help inactivate the virus," he noted. "The trick will be getting heat and dryness for disinfection. Rotate lots or areas, and allow one area to rest when pigs are in another area."
Despite the serious nature of PEDv, the disease is not a human or food safety risk. Every pig entering a USDA-inspected plant is inspected for signs of disease prior to slaughter, and hanging carcasses are inspected by USDA veterinarians.
Sundberg hopes that in a few years PEDv will be a disease that is only talked about, but he said, "Pigs trade a lot of pathogens, just like people do. The things we learn about PEDv now and apply in the future will help maintain the health of pigs and herds and will help maintain the health of the national industry. We are learning lessons from PEDv, but we're also learning biocontainment lessons that will apply in the future, whether or not we have PEDv."
More information on PEDv, including appropriate on-farm biosecurity and guidelines for biosecurity at shows and sales, is available at www.pork.org
. Additional information about PEDv, including suitable disinfectants, is available on the American Association of Swine Veterinarians website (www.aasv.org
The author is a frequent contributor and freelance writer who farms and raises Great Pyrenees in south-central Pennsylvania. Comment or question? Visit www.farmingforumsite.com and join in the discussions.
Photos courtesy of KCB Stock Farm.