Porcine Epidemic Diarrhea: is porcine blood plasma 'an open portal'?
Monday, August 4, 2014
Blood plasma makers are convinced that the contamination came from other sources, but veterinarians and producers are skeptical and, for now, are taking the feed off the menu
by DON STONEMAN
Ontario's pork industry has set a task for itself: bear down and wipe porcine epidemic diarrhea (PED) and Delta Corona Viruses out of infected barns before winter returns and the cold-loving viruses can regain the upper hand. It's an ambitious goal and not completely without controversy.
Dr. Doug MacDougald of South West Veterinary Services, the province's pre-eminent swine veterinary practice, described a protocol for elimination as a guest panelist during a "town hall" conference call sponsored by Alberta Pork for producers in late June. (At press time, no PED cases had been reported in that province.) MacDougald called into the conference from the office of a 3,000-sow barn in Middlesex County, which he had identified as the last farm to be infected with contaminated porcine blood plasma feed in mid-February.
"We are down to very low clinical signs," the vet said. Strenuous sanitation is de rigeur. The goal is to scrub away the virus before sows' immunity tails off, approximately 10-12 weeks after clinical infections end, and the animals are reinfected, as has happened in several other barns already.
MacDougald oversees swabbing for virus every week, sampling scouring litters, in shipping rooms, utility rooms, walkways – "everywhere a virus might be harboured or trapped. It can be anywhere." Recently, PED virus was found in an uncleansed freezer where dead pigs had been kept and also on a barn worker's boots. Sanitization, together with drying and whitewashing of hallways and rooms, is repeated. MacDougald told Alberta producers and industry representatives that "a high level of attention to detail is required" to eliminate disease in the barn. PED is "much tougher to eliminate than PRRS virus," he says.
The protocol also involves eliminating porcine-based protein products from feeds, and therein lies the friction point. The same week that MacDougald spoke to Alberta producers, porcine plasma makers were attempting to persuade balky Ontario practitioners to recommend that their products go back into weaner feeds. At South West Veterinary Services in Stratford, there were skeptics and no takers.
"They met with us last week and stand by the process that they use for (making spray-dried) plasma. They essentially say 'we've got clear proof that it is completely safe, that the contamination of plasma that infected 18 herds was not our problem and that it got cross-contaminated sometime after it left our plant.' And that is just bullshit," MacDougald told Better Pork.
As MacDougald explains, the original PCR (polymerase chain reaction) test by the Canadian Food Inspection Agency (CFIA) is capable of detecting PED virus particles in pigs, in the environment and in feed. The PCR test doesn't say if the virus is infectious; it may be deactivated or dead. In the follow-up test, a swine bioassay, the feedstuff is fed under controlled settings to pigs. If they get sick or replicate the virus, the feed is deemed to be infectious.
The CFIA performed a swine bioassay test on samples of the controversial feed and the test results were negative. It's that negative test result that plasma makers are hanging their hats on.
"A negative swine bioassay does not mean that PCR-positive feedstuff is not infected. It only means that a small amount of feed that got fed to a small amount of pigs is not infective," MacDougald asserts. "But if you feed it to thousands of pigs" and only one is infected, the virus that one pig expels will infect the rest of the herd.
In terms of epidemiology, the bioassay studies are meaningless, he says. The companies' argument "is not a valid argument, based on population science."
MacDougald says his practice's recommendations won't change until more questions are answered.
"Our (South West Veterinary's) position here is very clear – that we will not support feeding porcine or porcine products in feed until there is much more rigorous science on transmission vectors and how PED strain 1 and strain 2 and Delta Corona Virus arrived in the United States in one year. That is the reality in front of us, that we have an open portal for viruses to enter the swine industry and three of them have in the last year. Everything needs to be looked at, and feed is one of them."
(MacDougald's single exception to the no-porcine-product-feed rule is Canadian-sourced protein plasma manufactured before Dec. 31, 2013. He believes that this particular plasma product is safe for use, because it was made from blood from Canadian pigs before PEDv was found in this country, but he notes that the supply is running out.)
During the Alberta Pork telephone town hall meeting, producers were polled and 88 per cent indicated that they had quit using porcine feed products in their operation. It's not known if Ontario producers are taking the same advice. They have not been asked that question during Ontario Pork-sponsored town halls, says communications director Mary Jane Quinn. Ontario Pork's PED web page directs producers with questions about feed to consult with their veterinarian. MacDougald says his clients have quit using porcine products in feeds.
Good on paper
Veterinarian Dr. Frank Marshall of Marshall Swine Health Services in Alberta says that there are still questions unanswered about the feed-making process. "On paper, it looks good," he allows.
Marshall and Dr. Egan Brockhoff, owner of Prairie Swine Health Services in Red Deer, noted that Dr. John Harding, associate professor, swine production medicine at the University of Saskatchewan's Veterinary Medical Centre, spoke critically about feeding porcine-based feeds back to pigs in his opening remarks to the IPVS Congress earlier in June. He also drew broad comparisons to Bovine Spongiform Encephalopathy (BSE), which was spread by feeding bovine-sourced feed back to cattle.
Marshall doubts that Harding's comments "were well received by the people that supply our plasmas and animal proteins."
Indeed, a 13-page research report posted on the North American Spray Dried Blood and Plasma Producers Association website on June 16, shortly after the Congress, outlined studies that the plasma makers claim prove that their product is safe and was dismissive of veterinarians' concerns about the infectivity of feed, blaming "post-processing contamination."
Louis Russell, a past-president of the association and the CEO of American Protein Corp. (APC), the largest plasma feed maker, based in Ankeny, Iowa, says the June 16 report was not a response to Harding's comments. That report is a summary of studies that Russell says have been submitted to peer-reviewed scientific journals and he anticipates they will be published in due time.
Meanwhile, the blood plasma industry wants to make it clear that blood plasma products have been of great benefit to the pork industry. Other "high-quality" proteins, such as those made with dairy products, are not as beneficial to pig health and growth, he says.
Russell says that, after Harding's speech to the IPVS conference, porcine plasma industry representatives sat down with Harding and reviewed scientific reports. Russell says: "Our impression was his comments were more along the line of 'very compelling information and this information needs to be communicated to the industry.'"
Harding replies: "The epidemiological data from Ontario and bioassay work completed by the National Centre for Foreign Animal Disease (NCAD) showed a compelling association between plasma and the PEDv outbreak in Ontario. However, I have been shown data by APC on the manufacturing processes and lot numbers of plasma in question, and agree that there are a lot of uncertainties. I would encourage all parties involved to work together to solve this important issue as soon as possible."
June 16 is not the first time the plasma product makers have responded to criticism of their products in connection to the PED outbreak.
Posted on the website of the American Association of Swine Veterinarians is a document dated Feb. 11 (a week after the connection between PED and feed was first reported in Canada) from the North American Spray Dried Blood and Plasma Producers Association. "Based on current scientific evidence, the (plasma producers' association) concludes that properly sourced, collected and processed porcine blood and blood products are safe and do not contribute to the spread of PEDv." The report allows that its members "actively support continued research into the causes and control of this and other diseases."
Research projects launched
Research into key questions is being conducted in the United States and is being co-ordinated with research in Canada so that projects aren't duplicated. Dr. Lisa Becton, director of swine health information and research, National Pork Board in the United States, says eight different projects were funded in March, centring around feed, including a better way to determine if the virus is infective, if starlings are a possible vector for PEDv and Porcine Delta Corona Virus, as well as "mitigation factors" such as time and temperature in pelleted diets.
Another seven animal-focused proposals were selected for funding at the end of April. Those projects included developing ways to improve sow immunity and also more investigation into Delta Corona Virus. "We knew a lot about PED; we didn't know much about Delta Corona," Becton allows. "There are still a lot of questions as to how it got here in the first place."
According to its March 11 press release, the National Pork Board is collaborating with "a number of industry players," including the National Renderers Association and the North American Spray Dried Blood and Plasma Producers Association.
Alberta veterinarian Marshall says studies outlined at the IPVS Congress in Mexico show that sow immunity to PEDv gained by biofeedback does not last. Producers can expect sows to break with PEDv again if there is still virus in the barn nine to 12 weeks after feedback. "This helps explain some of what we have seen and heard in the United States," Marshall adds. If there isn't resurgence at 90-120 days after the first infection, then the environment in the barn has been cleaned up. That's what MacDougald is trying to achieve in the barn in Middlesex. He said at press time that a number of Ontario barns were near that crucial point. "There can be no letup" in sanitation, he says.
Marshall says the efforts MacDougald recommend are comparable to what had to be done in barns with Transmissible Gastro Enteritis (TGE) infections 15 years ago. Marshall describes PED as "TGE on steroids" in terms of the amount of virus put out by sick pigs.
According to the June 16 blood plasma producers' statement, "the primary route of infection is through direct contact with infected pigs or from the manure of infected pigs. Other routes of infection responsible for spreading the virus may be contaminated transport vehicles, farm equipment and farm workers and visitors. Industry leaders are actively discussing and reviewing data concerning the role of feed and feed ingredients in the spread of PEDv. Speculation that PEDv is spread by feed has led to implementation of costly biosecurity programs, often with little controlled research or data supporting the necessity or effectiveness of the program."
The June statement adds: "The first report of PEDv in Ontario and the subsequent investigation resulted in the belief that nursery feed containing porcine plasma may be the source of PEDv infections. The CFIA reported infective virus was detected in samples of porcine plasma, but infective virus could not be detected in the feed containing the porcine plasma. Even with this conflicting data, many industry professionals concluded spray-dried porcine plasma is spreading the disease. In addition, and despite the long history of indisputable performance benefits, some veterinarians have recommended removing spray-dried porcine plasma, and in some cases all porcine-based ingredients, from feed for swine."
For his part, MacDougald says: "The producers I deal with have stopped." He adds that porcine protein products were eliminated in February in a 2,500-sow, multi-site farrow-to-finish system he has helped manage for 15 years "without any loss in productivity."
In that system, weaning piglets once a week, aged between 16 and 22 days (an average of 19.5), average daily gain remains the same as does feed conversion "and very, very good performance. I was pleasantly surprised," MacDougald says. He adds that plasma "has been a very good product for early wean pigs" and in stress situations.
PED is now a reportable disease in the United States. The number of new cases is about 100 a week, compared to more than 300 in January and February, MacDougald says. For every 100 PED cases, there are 20 Delta Corona Virus cases recorded. However, the Alberta vets on the conference call are skeptical that all cases are being reported.
Brockhoff says the key will be what happens in the United States this fall; the pig-handling infrastructure is loaded with virus. MacDougald estimates that 60-75 per cent of U.S. sow inventory has been infected, including three-quarters of intensive operations. Some large integrated systems continue to use porcine-based feed products. He predicts the disease incidence will ramp up in the cold weather.
The challenge will be tougher in continuous-flow farrow-to-finish operations where all-in, all-out cleanouts can't be practised, says Mike DeGroot, technical services veterinarian for Ontario Pork. Ontario Pork has hired former swine specialist Ed Barrie to sample for PEDv in trailers at packing plants and assembly yards. The initial sampling efforts have proven negative, leading to optimism that there is little of the virus in the infrastructure here, unlike in the United States. BP
A $6-million settlement for the 2003 BSE case
When Bovine Spongiform Encephalopathy (BSE) was detected in a single Alberta cow in May 2003, the border slammed shut on Canada's export-dependent beef industry, which is finally in recovery more a decade later.
In a class action lawsuit initiated in 2005, beef producers sued Ridley Inc., the company alleged to have provided contaminated feed to the Alberta ranch. In 2008, Ridley reached a settlement agreement with producers, while admitting to no liability or wrongdoing, and deposited $6 million into a settlement trust fund. A producer suit against the federal government for failing to ban bone and meat meal in cattle feeds despite "signals" is ongoing. BP