Pig Virus Continues to Threaten Pig Herds
Since I last wrote about the Porcine Epidemic Diarrhea virus (PEDv) outbreak in the U.S. last October, there has been a lot of stuff going on. Pigs, veterinarians, farmers, and the USDA have all been very busy. Here’s the latest.
The virus that causes PED is part of the swine enteric coronavirus diseases (SECD). While PEDv was first documented in the U.S. in April 2013, another virus of the same family, called porcine delta coronavirus (PDCov), has also popped up. Both viruses cause diarrhea and associated weight loss. Both can result in significant mortality, primarily in young pigs.
Since its initial outbreak over a year ago, PEDv has killed roughly 10 percent of the pigs in the U.S. — that’s an estimated seven million pigs, according to a Reuters report in early June. What’s more, officials still don’t know where it came from. While there is speculation that its origin is from China, since all strains identified from the U.S. outbreaks are closely related to a strain from China, the where and why and how of its transcontinental travel remain a mystery, something unnerving to officials whose job it is to keep foreign animal diseases, well, foreign.
On June 5, 2014, the USDA issued a Federal Order. This Federal Order requires all producers, veterinarians, and diagnostic laboratories to report all new cases of PEDv and PDCoV. Secondly, this order requires hog operations to work with a veterinarian to develop a management plan to address the disease and prevent its spread in their herds. Both parts of this Federal Order are aimed at tracking the diseases and helping prevent their continual spread.
As a veterinarian — and large animal veterinarians are mostly affected by this — certain diseases (e.g., diseases the government is trying to eradicate, have already been eradicated, are foreign animal diseases, or dangerous zoonotic diseases) are reportable, which means that if you see it in a patient, you call your state veterinarian and report it. This means you’re suddenly playing with the big boys. This means that now, PEDv has been elevated to Big Boy status. Sort of exciting.
On June 16, the USDA announced issuance of a conditional license for a vaccine that may aid in the control of PED, making it the first of its kind. You may have noticed two things in that last sentence: the word “conditional” and the word “may.” Conditional licenses are issued sometimes when a disease threat is heavy and the need is severe. Such a vaccine has been proved to be safe, but how well it works (called its efficacy) has yet to be completely determined.
There’s a possibility that a conditional vaccine may not actually work well at all and after this is proven from actual use data, it will be removed from the market. This happened fairly recently with the conditional approval of a vaccine in horses against a protozoa that causes spinal damage (a disease called equine protozoa myelitis). This was extremely disappointing in the equine veterinary world because there is a great need for such a vaccine in the U.S. Think of a conditional license as a way to get something safe on the market fast when there is a need, using real world data to gather the rest of the efficacy data. This is why the USDA’s statement on June 16 says “may aid in the control.” They don’t know yet. But they have to try something.
One thing to keep in mind is that PEDv is not transmissible to humans or other animals and can’t be transmitted through eating meat from an infected animal. So we humans remain safe, at least in terms of PEDv. Watch this epidemic closely if you have an interest in the pork industry or epidemiology, as things are continuing to develop on an almost daily basis.
Dr. Anna O'Brien