PEDV Retrospective with Dr. Joe Crenshaw

At the time of the 2014 Canadian PED outbreak, an extensive epidemiological investigation was initiated. The results of the investigation were published in a series of papers and are commonly cited when discussing the risk of spreading disease through feed and feed ingredients.

However, considering everything that has been learned about PED since that time, it is appropriate to review the original epidemiology to determine if all risk factors were appropriately considered.

Upon closer examination, it becomes apparent that several risk factors were not included in the original epidemiology. Today it’s well recognized that truck cleaning protocols, truck traffic, animal movement and other cross contamination possibilities exist. Had these factors been included in the original epidemiology investigation, the conclusions may have been different.

PEDV had a huge impact on the swine industry with millions of nursing pigs lost. The outbreak created a lot of panic because of this devastating disease. Industry stakeholders were looking for the potential source of the virus.

During the CFIA investigation in 2014, a swine bioassay showed porcine plasma collected from a feed mill contained infective PEDV, but feed containing the plasma was not infective so the investigators concluded the virus was introduced to Canada by contaminated porcine plasma. However, by the time CFIA sampled the porcine plasma at the feed mill, all remaining bags had already been sampled by two other groups several times. It’s known that multiple sampling increases the risk of cross-contamination, which certainly could have affected the results of the bioassay.

Further, during that time in 2014, FDA inspected our plant, reviewed processing records, took retained samples of the lot number in question and did their own bioassay. The pigs did not become infected, although the plasma contained virus genome by PCR testing. This points out that the plasma that showed infective in the Canada bioassay, was contaminated with infective virus after it left our facility or during the collection of the samples at the feed mill. We must remember that a PCR test only determines if virus genome is present, but it does not determine if the virus can cause infection. Since then several studies have shown that feeding PED genome positive plasma does not cause pigs to get infected with PED.

As an industry we have a much better understanding of how diseases such as PED are transmitted. While the initial results pointed to contaminated feed or feed ingredients, we now realize several additional risk factors were overlooked. For example, trucks from Canada were delivering pigs to the United States for slaughter and then returning to Canada while only being cleaned with a broom and shovel. Feed trucks delivering from farm to farm have the opportunity to spread viruses. Animal movement and contact with contaminated assembly yards plays a role. Research since then has demonstrated all of these risk factors can contribute to disease transmission.

At the time, there were misconceptions about how plasma was collected. There wasn’t a thorough understanding about the hygienic methods of collecting and processing. We sought input from a broad cross section of the swine industry to better understand their perceptions and help us address their concerns while becoming more transparent about how we manufacture plasma. We reviewed every aspect of our plasma production process and manufacturing plants. We invested in enhanced biosecurity features, strengthened SOP’s, further separated wet and dry sides of the plant, increased employee training and implemented extended storage times.

Additionally, more scientific research has been conducted with PED and other diseases of concern for the swine industry. Through that research, we have been able to further validate that viruses of concern for the swine industry can be inactivated through a multiple hurdle approach to manufacturing, using a combination of UV processing, spray drying technology and post-drying storage at room temperature.

We understand that it’s important to invest in biosafety research, multiple hurdle processing technologies and to continue to work hard to educate the industry.