Is Feed To Blame For Spread of PEDv?

Wall Street Journal:

With a dearth of solid leads, investigators are exploring whether something in pig feed could be a conduit for porcine epidemic diarrhea virus, which has spread to 27 states and killed millions of young pigs since it was first identified in the U.S. last April. One focus of the inquiry: porcine plasma, a widely used feed ingredient made from the blood of slaughtered hogs and fed to piglets.
The U.S. Food and Drug Administration, the Agriculture Department and pork-industry officials are examining a range of feed ingredients and manufacturing processes as well as other possible pathways for the virus, like contaminated air or dust particles carried from farm to farm.
Though the evidence is inconclusive, some researchers say that porcine plasma could be spreading the virus from adult pigs that show few symptoms, or that some plasma may have been contaminated in transit.
The ingredient has been a mainstay of piglet diets in the U.S. since the 1990s, after scientists discovered it provided antibodies to protect young pigs from disease and helped them switch from feeding from their mother to the grain-heavy diet common on livestock farms.
Last month, the Canadian Food Inspection Agency disclosed that it had found plasma contaminated with the virus, after multiple hog farms in Ontario that were hit by PED, and another farm on Prince Edward Island with a suspected case, all reported that they bought feed from the same vendor, Ontario-based Grand Valley Fortifiers.
The Canadian agency said that the virus was present in plasma that originated in the U.S. and was obtained at the company that manufactured Grand Valley's feed, which the agency has declined to identify. It said the plasma contained virus "capable of causing disease in pigs."
Earlier this month, however, the agency said laboratory tests in which it fed Grand Valley's feed pellets to piglets failed to demonstrate that the feed, which contained plasma and many other ingredients, could cause infection.

I didn't know that porcine plasma was processed and added into hog feed. It would seem like the processing would destroy the virus. I heard somebody say that even after cleaning a barn out and letting it sit empty for several months, the disease shows up in a new crop of pigs. It doesn't sound good when scientists aren't sure what is causing PEDv to spread so far.