The viral disease is caused by a porcine coronavirus and can take a major toll on a swine operation. It can lead to vomiting and occasional diarrhea in sows and gilts and severe diarrhea and vomiting in nursing and recently weaned pigs, according to Kansas State University's College of Veterinary Medicine (click here). The disease can spread quickly and can eventually lead to severe sickness and death.

"The disease is a new introduction into the United States, so we have a population of pigs that are highly susceptible," said Steve Dritz, K-State swine veterinarian. "When it's introduced, especially into a sow farm, we have losses of up to 100 per cent of the baby piglets for multiple weeks. Economically, it's quite devastating. Some estimates show that maybe as high as five per cent of the U.S. pig population has been lost to this disease now."

Dr Dritz said that the disease has been found in Kansas, but because pig farms are more widespread in Kansas compared to other parts of the country, the impact has not been as severe as other areas.

PEDv can be transported farm-to-farm by people carrying the disease on boots and clothing, or by trucks that transport pigs from multiple farms to slaughter facilities, for example. Most recently, PEDv has been linked to a common feed ingredient in early weaning diets - porcine plasma protein. This discovery happened within the past few weeks in Canada.

"Canada had the first reported outbreak of PEDv this year in late January, in the province of Ontario," Dr Dritz said. "There are a lot of pigs and pig transport trucks that move back and forth between Canada and the United States, so Canadian veterinarians were concerned about the risk of introduction of the disease from the United States into Canada. They did quite a bit of surveillance and monitoring prior to the first case."

A majority of the cases that were initially reported in Ontario, he said, had biosecurity practices in place but were still experiencing unexplained outbreaks. That led investigators to look at other routes of transmission besides pigs, pig transport trucks or people. Among the routes that immediately came to mind was through feed transport vehicles, feed and feed ingredients.

Dr Dritz said many of the farms in Ontario that were initially confirmed with PEDv infection used a common feed company. The investigators examined if feed trucks traveling to and from the different farms could be transferring the disease from an infected farm to an uninfected farm. They were unable to establish that link, so the next step was investigating the feed ingredients.

"The one ingredient that was common was porcine plasma protein, which is commonly fed to baby pigs in creep diets, or in early weaning diets," he said. "It's a very good protein source for baby pigs, to help them transition through the weaning process."

Take a look at feed ingredients

Plasma protein, according to the University of Kentucky (click here), is dried plasma from cattle or pig blood that is collected at slaughter facilities throughout the United States. The plasma is separated from the blood and goes through a drying process before being shipped as a feed ingredient. The product provides many nutritional benefits to young pigs at weaning, as it enhances growth rate and feed intake.

In the recent investigation in Canada, the presence of the virus in the porcine plasma protein was identified by a polymerase chain reaction (PCR) test, a highly sensitive test that measures genetic material, Dr Dritz said. The test can determine the existence of the virus, which theoretically could be inactive, and therefore, not be infective. In this case, it could be fed to pigs and not cause them to become ill.

"The products go through processes that should inactivate the virus, but similar to salmonella with some feed ingredients, you get cross-contamination, for instance, if a truck that was contaminated touches the product," Dr Dritz said. "We're seeing suppliers of these types of ingredients starting to reexamine their processes. We think a majority of these ingredients are probably not infective, but there may be some that are."

In addition to looking closer at potential cross-contamination and feed ingredient processing, the investigators in Canada also took the next step of taking a potentially infectious porcine plasma protein product and feeding it to susceptible pigs, he said. Those pigs reproduced the disease, which provided strong evidence to link transmission through feed.

"We're trying to help producers by providing them with nutritional options," Dr Dritz said. "Many in the industry have decided that this is a potential route of transmission and want to eliminate the route as a risk. So, many swine producers are eliminating porcine protein sources out of sow farms and diets for baby pigs."

Dr Dritz said a lot has been learned from the Canadian case, but there are many questions yet to be answered. While researchers address the questions, producers should be familiar with their feed ingredients and do a risk assessment for their potential as a route of disease transmission.

"We see our role as providing information and options, and we're working to figure out research questions and get research initiated to find answers," Dr Dritz said.

The National Pork Board reports that although the virus can be deadly to young, susceptible pigs, it is not zoonotic. It poses no risk to other animals or humans, nor does it affect the safety of pork products.