According to Dr. Chris Byra, the manager of the Canadian Swine Health Intelligence, contaminated feed has been shown to be the most likely cause of the PED outbreak in Ontario. The farms that became infected were linked by a single source of feed and a single batch of plasma and the biosecurity on some of these farms was very good and there were no other links.
What really kind of sealed it from an epidemiological point of view was finding a positive case in PEI which had absolutely no link with Ontario at all but had purchased feed from that batch from the same supplier. The overwhelming epidemiological evidence already confirms that feed was a high risk.
Subsequent to that the plasma and feed were tested and samples of both were found to be positive. The plasma was tested in live pigs in a bioassay and did cause disease.
The feed samples that were used for that bioassay were marginally positive, dubious positives they were called, and did not cause disease.
Dr. Byra stresses that finding absolutely does not negate that everything else points to feed.
He says further testing would be needed, you would need more samples fed for more time and they would have to be samples that were strongly positive to start with.
Monday April 14, 2014/ Farmscape/ Canada.