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PRRS Projects Yield Mixed Results

PRRS Projects Yield Mixed Results

This roundup outlines the results of seven Midwestern porcine reproductive and respiratory (PRRS) eradication projects. 


Within the last few years or so, organized efforts to control and eventually eradicate porcine reproductive and respiratory syndrome (PRRS) from areas around the country have sprung up, concentrated in the Midwest.

Results from seven of those projects, which have produced mixed results, are outlined below.


Illinois (Project #1)

The western Illinois tri-county regional PRRS control project is comprised of Hancock, Adams and McDonough counties, known as the HAMproject.

The project had five goals:

1.     Identify swine populations within the three counties.

2.     Establish PRRS status based on published categories: PRRS positive, PRRS stable or PRRS negative.

3.     Use risk assessment tools to evaluate and develop producer biosecurity.

4.     Engage multiple stakeholders.

5.     Establish progress toward control and elimination of PRRS.

Many of the original goals were met. Swine populations in the three counties have been mapped; 174 swine farm sites were identified (Table 1) and 116 described as “active.” Multiple stakeholders were engaged, both independent producers and large production systems.


Table 1. Western Illinois PRRS Control Project Status

PRRS Status               Total

Negative                      31

Positive                       23

Positive stable             4

Unknown                    58

Empty                         51

Trucking                      2

Buying station             5

Total                           174



A large number of the production sites are affiliated with one of four modern production systems. TriOak Foods, a partner in the HAM project, financed a plane and pilot to map McDonough County. This analysis revealed flying was more economical than driving to identify swine production locations. Hancock and Adams counties were mapped by driving and using Google Earth and plat books.

Of the 116 active sites, 58 are of known PRRS status, with continued PRRS monitoring to assess disease control methods in place. Twenty sites are routinely monitored and committed to being PRRS negative. These sites fund their own PRRS testing. The other sites and unknown status sites rely on funding from PRRS CAP or other funding from the U.S. Department of Agriculture to support PRRS testing.

Over time, producer participation and mindset about managing PRRS has changed, which has led project directors to reevaluate the focus of the HAM project from PRRS elimination to PRRS control (Table 2).


Table 2. Producer Attitudes in the Western Illinois Project

Mindset on PRRS       Number of Sites

Control                        14

Eradication                  28

Positive                       16

Unknown                    54

Non-participant           4

Empty                         51

Buying Station            5

Trucking                      2

Total                            174 


“The project directors would like to discover why producers have a particular mindset toward PRRS and how to manage it,” explains project leader Dyneah Classen, DVM, Carthage (IL) Veterinary Service, Ltd. “There are producers who individually prefer to control and eliminate the virus from their herds and would like to see regional elimination. There are producers who choose to live PRRS positive and ignore the cost. And there are producers who choose not to participate in PRRS control/elimination programs.”

As a result of changing views about PRRS, the goals of the HAM project have been revised to discover:

1.     What makes this mindset group toward PRRS unique.

2.     How each mindset toward PRRS has an impact on the global economic risk of shedding PRRS virus.

3.     Documentation of effective PRRS control methods in the ecosystem.

Independent producers have historically worked with groups and it was thought they would continue to do so to determine the status of their site if unknown. Most producers have accepted the project, but a “producer champion” is needed to lead a grassroots effort.

Differing mindsets in the project area have taken the project in a new direction to explore the sociology behind these different mindsets.

As long as different mindsets exist toward PRRS management, it will remain difficult to control and ultimately eliminate the virus from the three-county area.


Illinois (Project #2)

PRRS has defined the lives of the 40-50 producers in Dekalb County and the surrounding area, which have been working to control and eliminate the disease for the last two years.

The coordinated project to clean up the virus began when a genetic change for a majority of producers in the area prompted a new way of thinking about PRRS, according to project leader Noel Garbes, DVM, Sycamore, IL.

Previously a PRRS-positive area, producers were content to simply “live with the virus.” The goal was to remain stable. But new and more virulent strains have plagued the industry in recent years and made the goal difficult.

As a result, over 80 sites housing swine (25 sites with sows, the rest finishing) have worked to change their PRRS status, with nearly all undergoing some form of PRRS control and many pursuing full elimination plans. Over 85% of the pigs and 90% of the producers in the area are participating in the project.

Participation simply means sharing PRRS status with other producers and key stakeholders. The next step is active control and PRRS elimination, and over 20 producers have taken this step completing:

--Thirteen sow herd closures (rollovers);

--Five (sites) depopulation-repopulation;

--Filtration of a boar stud and a gilt developer;

--Alternative weaned pig flow routing of 35,000 pigs/year; and

--Bubble depopulation and vaccination plans on five finishing sites. Bubble population at Bethany Animal Hospital in Sycamore, IL, means 60 days of no pig entries into the system to allow shedding of the PRRS virus on the farm to die down.

Despite vast improvements in biosecurity, PRRS breaks continue to occur. Producers work to contain breaks on their farms and the veterinary research team works to communicate and decrease potential risk of spread beyond the initial outbreak.

This project requires constant vigilance against a disease that wears on individuals financially and emotionally. But success can be seen in improved reproductive and finishing performance of herds that have taken action to control PRRS. As a result, new strain introductions into the area have decreased compared to the previous five-year period.


Iowa Project

A PRRS control project for Iowa County, IA, was initiated in August 2010, with the goal of establishing a replicable regional porcine reproductive and respiratory syndrome (PRRS) virus control and elimination model for an area which has both locally owned pig production and a significant influx of non-locally produced growing pigs.

Twenty of 26 active production sites have enrolled in the research project, according to project leader Derald Holtkamp, DVM, Iowa State University.

A major obstacle of the project was public sharing PRRS virus status, but producers now realize that sharing this information has raised awareness of PRRS.

Since starting this research project, producers have learned to be more alert and better manage biosecurity through the use of Production Animal Disease Risk Assessment Program (PADRAP) managed at Iowa State.

For example, grow-finish producers are focusing on how to decrease PRRS risk when transporting swine to market. Producers have also learned that routine monitoring and development of herd plans will help exclude the virus from the farm.

Despite its successes, the Iowa County research project faces challenges, such as understanding the impact of PRRS-positive growing pigs entering the county. Several contract finishers receive PRRS-positive pigs.

Producers want to be PRRS negative, but some had given up because the disease is pervasive and easy to acquire. Some are rethinking their position.

This research project has provided the opportunity to collaborate to eliminate the virus from individual sites and improve biosecurity practices of bio-exclusion, bio-management and bio-containment.

The effort also offers an opportunity to learn about what local factors contribute to area spread, importance of source herd status for feeder pigs and industry steps to better manage these risks.


Michigan Project

The area regional control project for PRRS involves two counties in west central Michigan which have a high density of pork production.

Fortunately, this area has several natural geographic boundaries which make it very attractive for control of the disease.

Another key fact is that there are very few pigs of unknown or positive status that are moved into the area to be fed out.

The PRRS research project was started in August 2008. Nearly all of the active production sites were tested in the summer of 2009 and many completed the Production Animal Disease Risk Assessment Program to better manage biosecurity.

The first round of testing produced few surprises. All of the individual viruses found were sequenced to determine if the same virus was moving around certain areas. There did not appear to be significant movement between neighboring sites.

Test results were used to develop individual herd control plans, concentrating on improving immunity and controlling exposure in sow farms. “A very important step was to critically evaluate the replacement gilt protocols to gain stability in these sow herds,” points out project leader James Kober, DVM, Holland, MI.

Finishing sites receiving negative pigs have been able to totally empty their facilities and most have remained negative.

Only two sow herds experienced active PRRS virus last winter. There have been no known clinical breaks in negative herds.

Funding has come from two PRRS-CAP (Coordinated Agricultural Project) grants provided by the U.S. Department of Agriculture.


Minnesota Project

When the PRRS elimination project in the “North 212” region started in Minnesota in 2004, it was limited to elimination of the virus from Stevens County. Then it was expanded to surrounding counties and from there to the region north of Hwy 212.

The region of North 212 offers unique opportunities for the overall goal to work with producers and veterinarians to identify, control and eliminate the PRRS virus from infected premises. The region features areas with low density of farms, working with producers under the guidance of a voluntary program and implementing risk-based surveillance methods.

More than 400 sites have been identified; about half are participating in the research project. Current challenges include identification of sites, producer participation and disclosure of herd status and dealing with new infections in areas of low prevalence.

“We have learned that communication is important and that producer leadership at a local level is a must,” says PRRS project coordinator Dave Wright, DVM, University of Minnesota. “We have also learned that having PRRS-free areas provides real economic advantages to producers.”

The primary goal of the research project is to continue expanding the PRRS control and elimination efforts across the North 212 region and throughout Minnesota. Second goal is to implement a more comprehensive, risk-based surveillance program that meets the demands of a voluntary program for disease elimination.


Nebraska Project

Area regional control program for PRRS located in Cuming County in the northeast Nebraska started off slow in 2010, but has accelerated in 2011, with participation rate climbing to about 70%, says project leader Alan Snodgrass, DVM, West Point, NE.

About 200 pig sites were identified, plus 70 more sites that feed pigs periodically. The periodic finishers plus numerous barns in the southern part of the county that feed open-market pigs of unknown status has caused issues in keeping Production Animal Disease Reporting Risk Assessment Program (PADRAP) current for biosecurity practices needed to exclude the PRRS virus.

Communication is essential to the success of this project. With the help of Boehringer Ingelheim Vetmedica Inc., producers are made aware of changes in the herd health status via e-mail or text messaging. This allows producers to make quick decisions regarding biosecurity or animal movement, and hopefully will improve communication among producers.

Project organizers have started to form clusters and producers are working within their cluster to implement control measures, such as herd closure, vaccination or in some cases, depopulation. Clusters are organized based upon geographical location or similar source farms.

Plans to include less-dense counties to the east and north in the control project are being considered.


Pennsylvania Project

Pennsylvania pork producers were skeptical about the idea of a PRRS area control plan back in 2007, when the Pennsylvania Department of Agriculture provided funds for the University of Pennsylvania School of Veterinary Medicine (VMD) to explore the prospects.

However, progress with PRRS control on individual farms has yielded a growing interest in the possibility of area control.

The project has mapped over 500 sites accounting for about 80% of the pigs produced in Pennsylvania, and continues to track their PRRS status.

The diversity of pork production reinforces the notion that different control strategies may be required for different geographical areas in the state. This diversity may be applicable to other states or regions with similar features.

“Perhaps surprisingly, molecular epidemiological studies on the PRRS virus strains in Pennsylvania provide little evidence for area spread of the disease, and implicate animals or personnel as the major vector of PRRS transmission,” reports project leader Tom Parsons, VMD, University of Pennsylvania.

Regional biosecurity plans are being formulated to help maintain areas identified as PRRS-free.

Novel approaches are underway to identify the remaining 20% of the pigs in Pennsylvania and determine their PRRS status, as well as develop a long-term financially sustainable model for area control of PRRS.

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