The battle to eradicate PED from the Ontario swine herd

Sunday, April 5, 2015

Though the target of eliminating the PED virus by November 2014 has come and gone, the fact that, at the time of writing, more than 90 per cent of primary and secondarily-infected cases had already been eliminated, or were in the process of being so, is a remarkable achievement

by ERNEST SANFORD

On Jan. 22, 2014, the first case of PED in Canada was identified in a farrow-to-finish herd in southwestern Ontario. As a large number of the Ontario and Canadian swine community was assembled in Banff, Alta., for the annual Banff Pork Seminar, we all got the news at the same time.

It would be an understatement to say that it sent shockwaves through the audience. It was a huge initial disappointment as the industry had worked very hard, and successfully, to keep PED out of Canada since the first case was diagnosed in the United States in May 2013, nearly nine months previously (actually 10 months, since retrospective tests determined that the first known U.S. case of PED had actually been in April 2013).

Biosecurity was ratcheted up across Canada. Biosecurity training and enhancements had been a major emphasis in the Canadian Swine Health Board's approach to protecting the Canadian swine herd from unwanted and unwelcomed intrusions of diseases. Trucks returning after deliveries of weaned, grower or market hogs to the United States, especially back into Manitoba and Ontario, were immediately identified as the major risks for bringing PED virus (PEDv) into Canada.

Collaboration among the provincial pork boards, the Canadian Food Inspection Agency (CFIA), provincial governments and veterinarians targeted trucking for extensive coverage on biosecurity. The livestock truckers responded admirably to the call for vigilance, washing, disinfecting and drying trucks on return to Canada from deliveries in the United States.

Even so over the next several days and weeks after the initial PED case in Ontario, more cases of PED were confirmed in the province, including areas that were clearly outside the traditional pig-producing areas of southwestern Ontario. Furthermore, the outbreaks were being reported in sow herds and nurseries, not in finishing barns – as would have been expected if trucks returning from the United States had brought the PEDv into Canada.

Then the even more inexplicable happened. A single herd in Prince Edward Island got infected. After the negative returns in pig production over the previous five to seven years, liquidations had almost entirely wiped out pork production on the island, leaving it with very few pig herds.

But the picture cleared up very quickly. A single shipment of porcine spray-dried blood plasma (PSDBP) from the United States was contaminated with the PEDv. All of the first 17 herds infected in Ontario had recently used that single source of PSDBP for their nursery pig feeds. The herd in PEI was the only herd using this same source of PSDBP.

This single shipment negated all the biosecurity efforts by creating a backdoor for entry of the virus into the Canadian swine herd over which biosecurity measures had no control. On the heels of the PEI infection, pigs in a Quebec finishing barn were confirmed PEDv-positive on Feb. 22, 2014. PEDv infection in two herds in Manitoba followed very quickly. Infection has since turned up in two more herds in Manitoba and more recently in several more herds in Quebec.

Surveillance testing in the major pork-producing provinces revealed, as would be expected, positive PEDv samples in high traffic areas, such as slaughter plants and hog assembly yards. Primary infections have occurred in 69 herds in Ontario. These involved 32 sow herds, nine nurseries or wean-to-finish herds and 28 finishers infected from primarily-infected sows herds at weaning.

Once the source of PEDv in PSDBP had been identified, the company importing the PSDBP into Canada ordered an immediate nationwide withdrawal of the product.

Alter the initial shock, the industry galvanized forces to combat this new disease threat. Practising veterinarians, experts from the Ontario agriculture ministry, the University of Guelph, the Animal Health Laboratory (AHL), CFIA, Agriculture and Agri-Food Canada (AFFC), Ontario Pork (OP) and the Ontario Swine Health Advisory Board (OSHAB) all put their collective heads together to develop a plan to contain and possibly eliminate the PEDv from Ontario.

OSHAB set a target for elimination of the virus from all infected Ontario herds by the end of November 2014. To back this target up, OSHAB established a province-wide PED area regional control and elimination program (PED ARC&E), which all herds confirmed PEDv-positive were invited to join. The goal for all these infected herds was elimination of the PEDv. To date, 100 of the more than 150 infected sites of the PEDv-positive herds have signed up and enrolled in the PED ARC&E program and set themselves on a course of elimination of the virus from their herds.

Of those enrolled, 42 are primary PEDv-infected sites. Producers have been successful in eliminating PEDv from 32 of the 42 primary sites. This includes three sites co-infected with porcine deltacoronavirus (PDCoV), from which both PEDv and PDCoV have been eliminated. An additional three herds with only PDCoV infection are in the process of eliminating that disease.

A total of 66 primary PEDv-infected herds in Ontario stayed infected for most of the summer of 2014. For nearly a four-month period commencing on July 21, 2014, there were no new cases of PED in Ontario until a farrow-to-finish herd in Middlesex County broke with the disease on Nov. 10, followed shortly thereafter by a break in a finishing barn in Niagara Region.

A total of five new PED cases were reported between July 21 and Dec. 31, raising fears that, as we got deeper into the colder months, we could be facing increased numbers of new outbreaks. Then, in the last week of January 2015, two PED breaks occurred in farrow-to-finish herds in Ontario.

After a period of nearly a year with no new cases of PED in Quebec, eight new PED cases also occurred in that month, all epidemiologically linked to the first of the eight cases in early January.

So what is the likelihood of PED being totally eliminated from Ontario herds? The original November deadline has come and gone without complete elimination of PEDv. That takes us into winter and we'll probably have to wait until spring before thoughts of complete elimination can be realistically resurrected. Once the more favourable warmer weather returns in spring, a hard push would be expected to eliminate both PEDv and PDCoV from the remaining infected herds. At time of writing, however, it is estimated that more than 90 per cent of primary and secondarily-infected cases had already successfully eliminated PEDv or were well in the process of elimination.

Attention to piglet management, sanitation, feedback measures to enhance breeding herd immunity and concerted efforts to prevent the virus from moving around within a barn are key initiatives in achieving success in containment and elimination of the virus.

It has been a remarkable achievement to have eliminated the PEDVv from so many herds in so short a period. Especially rewarding has been the success in elimination of PEDv from farrow-to-finish herds, traditionally identified as the most difficult type of herd to eliminate this or most other diseases.

In the meantime, the work to prevent further infection of herds and to contain the virus from spreading from infected to uninfected herds continues in earnest. BP

S. Ernest Sanford, DVM, Dip Path, Diplomate ACVP, is a swine veterinary consultant based in Guelph