Better Pork - June 2007

Herd Health

The PRRS Project:
A comprehensive step in controlling the disease

Among other things, the project will map the prevalence of PRRS across the province and provide a scorecard for control and elimination activities instituted by the industry

by S. ERNEST SANFORD

Two years ago, the initiative commonly known as “The PRRS Project” was launched after a winter in which a large number of devastating PRRS outbreaks occurred across southwestern Ontario.

Much has happened relatively quietly since then and much more is in the pipeline. This update will quickly chart the course “The PRRS Project” has taken over the last two years.

The project is administered by the OPIC Swine Health Advisory Board (OSHAB). OSHAB’s role initially was directed solely at PRRS. As Porcine Circovirus (PCV2) assumed a commanding position in the Ontario industry, requests and pleas arose from several quarters for OSHAB to include PCV2 in its mandate. Hence, OSHAB took on an expanded mandate which is to take a leadership role for major swine health issues in Ontario by:
• Providing direction for primary research and resource allocation;
• Advancing industry communication;
• Fostering collaboration among sectors and jurisdictions.

The OSHAB board is made up of representatives from the various sectors of the pork industry – producers (Ontario Pork and individual producers), feed industry, academics, packers/ processors, AI and breeding companies and veterinarians.

The PRRS Project’s original goal was to develop, over a three-year period, an understanding of how the PRRS virus is moving, spreading and changing among herds in Ontario.

This is a very broad, all-encompassing goal. To accomplish this, the project has several interrelated and interconnected initiatives. Figure 1 on page 68 is a schematic displaying some of the key, ongoing PRRS initiatives being co-ordinated by OSHAB. 

The most visible and most advanced of these is the one colloquially known as Project One: The PRRS Mapping Project, being conducted by a team of University of Guelph researchers led by Dr. Cate Dewey and her colleagues, Dr. Beth Young and graduate students Zvonimir Poljak and Thomas Rosendal.

The PRRS Mapping Project is divided into three information collection schemes:
• Collection of epidemiological information;
• Collection of PRRS virus sequencing information;
• Collection of spatial (geographic) information.

At the time of writing, information from 356 herds had been included in the epidemiological database. Of these, 305 are case herds (herds that had PRRS outbreaks) and 51 are control herds (no PRRS outbreaks). The data cover a full range of historical information of each herd.

The PRRS viruses from all of the 305 herd outbreaks have been sequenced to determine each one’s genetic makeup and the sequence information is added to the database. As for the collection of spatial information, it consists of identifying the geographical location of each herd’s PRRS virus and its relation to other genetically similar (and different) PRRS viruses in other herds in Ontario.

The historical/epidemiological information is then combined with the genetic sequence information and the geographical location, all linked together on a map (Figure 2). This allows the researchers to identify strains of virus that are forming clusters of outbreaks in a particular area, or are linked by one or several other common paths (e.g. movement of breeding stock, trucks, people, aerosol, etc.).

These linkages may also eventually be able to be extended to identify commonalities with the same strains of the virus located in other provinces and states. The goal would then be to use this information to chart courses that prevent the virus from jumping from herd to herd and creating the devastating outbreaks we have too often seen.

Going hand in hand with the mapping project is the benchmarking project, also initiated by OSHAB, which measures PRRS virus prevalence in herds in Ontario. The idea here is that we have to know and measure where we are over time so that we know if we are making progress. Thus, changes in prevalence in herds will provide a scorecard for PRRS control and elimination activities instituted by the industry.

Prevalence data are being collected semi-annually and are classified according to barn flow (e.g. farrow-to-finish, farrow-to-wean). PRRS prevalence by barn flow is categorized as “PRRS-positive,” “PRRS-negative,” or “Unknown” (Table 1). The prevalence data will also document successes of elimination strategies and provide an objective basis for calculating the economic impact of PRRS in Ontario.

A PRRS elimination tool kit is being developed for producers and the industry to use in the PRRS elimination effort at the individual herd level. The tool kit will be a centralized “go-to” source for information on strategies for elimination of PRRS virus at the herd level. These elimination strategies will be confined to those which have been critically evaluated for scientific merit and will include sufficient detail to assist with effective decision making by producers.

An ongoing series of case studies commenced back in the April 2007 issue of Better Pork (see pages 8-16) and continues in this and future issues (see pages 20-30 of this issue). The case studies cover real-time production and performance data depicting both successes and failures of PRRS control and elimination strategies.

Several herds have been enrolled for these case studies. Their stories and data will be plugged in and updated to follow the course of events as the situation in each herd changes over time. 

PRRS Risk Assessment
Training sessions on use of a PRRS Risk Assessment (PRA) tool have been planned, at the time of writing, to be taken by about 30 Ontario and other Canadian swine veterinarians in April 2007. The PRA tool, created by Boehringer Ingelheim, was gifted to the American Association of Swine Veterinarians (AASV) for the use of swine veterinarians to determine the risks of PRRS virus infection from external and internal sources and activities of herds.

Establishing PRRS risk is seen as an integral step in understanding where the gaps are in biosecurity, both within the herd and from outside the herd. Once the risks are identified, then the necessary steps can be taken to eliminate or minimize those risks. This knowledge will be crucial in preventing re-infections of a herd after it has successfully gone through a PRRS eradication.

Understandably, all this requires considerable resources. The industry as a whole has stepped forward and laid the foundation that has allowed the project to proceed. Ontario Pork has funded Project One: The PRRS Mapping Project in its entirety, contributing $299,000.

A three-year project started in 2005 and totalling $276,000 has been funded by industry funds matched by a grant from CanAdvance, Agriculture and Agri-Food Canada program that helps producers, groups and business interests expand or enhance their operations, to compete on a regional, national or global scale. CanAdvance’s grant contribution is $117,000 and industry’s $159,000. Overall pledges by industry over the three-year period total $260,000. (This figure includes the $159,000 above).

Over the last two years, information has been disseminated to industry personnel and all stakeholders via a variety of avenues. Several information meetings have been held, updates published and press releases announced periodically.

Four Big Bug Day scientific conferences have been conducted over the last two years. These conferences have become a standard for informing and updating on scientific and other aspects of PRRS control and elimination and on efforts to combat Porcine Circovirus. Big Bug Days are held twice a year, spring and fall, and are starting to attract attention and attendance from out-of-province participants. 

As part of the country-wide and North American focus on PRRS, Dr. Scott Dee, president of the American Association of Swine Veterinarians (AASV), joined the OSHAB board in 2006.

Dr. Dee was so impressed with the industry-wide structure of OSHAB and the PRRS Project that he adopted several OSHAB concepts in his Minnesota PRRS eradication efforts. The OSHAB model was then included in the AASV’s newly formed North American PRRS Eradication Task Force. BP

S. Ernest Sanford, DVM, Dip. Path., Diplomate ACVP, is a swine specialist with Boehringer Ingelheim Vetmedica (Canada) in Burlington. Email:esanford@bur.boehringer-ingelheim.com