Vet’s dream: No PRRS in 2030

Scott Dee is a veterinarian on a mission: To eradicate pork reproduction and respiratory disease syndrome virus from state and U.S. swine herds over the next 20 years.

It’s possible, he says, because all inputs needed for elimination are here and available for scientists, veterinarians and producers.

Key Points

• Filtered, mechanically ventilated barns protect pigs from PRRS.

• U-M veterinarian believes the disease can be eradicated across the U.S.

• Control efforts must be collaborative, voluntary and science-based.


Dee, a veterinarian at the University of Minnesota Swine Disease Eradication Center, has spent more than two decades studying the disease and collaborating with other researchers to find a way to eliminate it from herds. For the last four years, he has led a project in west-central Minnesota that created a production region model involving a 300-head research farm. The mechanically ventilated finishing barn was infected with a specific PRRS strain and closely located among three other farms, two with mechanical filter systems and one without.

From June 1, 2006, and until Sept. 20, more than 4,700 pigs were involved in the project. Researchers measured airborne transmission and airborne transport of PRRS and took a total of 32,207 samples from the air, pigs, people, vehicles and insects. In the non-filtered barn, they identified PRRS 33 times. In barns with added air infiltration, they found none. Mechanical and electrostatic filtration was the most effective in keeping PRRS out.

Putting it into practice

While overseeing this project, Dee began working with veterinarians at Pipestone Veterinary Clinic, Fairmont Veterinary Clinic and the Swine Vet Center to put the concept into practice on commercial hog farms. Currently, they are two years into a four-year study that involves an evolving number of filtered barns.

“We’ve got 10 filtered and 26 non-filtered farms now, but it’s changing,” Dee says. “People want to get their barns filtered.”

Of the 10 filtered barns, eight have remained uninfected with PRRS. Two have had trouble with the disease, due to a breakdown in biosecurity. On one farm, PRRS entered via transport and on the other, an employee breached security.

“Some might say those were failures,” Dee says. “Not so. With more than 3,000 sows per farm in a dense pig farming area under heavy siege, those filtered farms before had one infection every seven months or one every 12 months.”

He adds: “Filters aren’t magic. They will stop the airborne route, but the virus can get in other ways.”

Of the 26 non-filtered barns over a two-year period, 13 have been infected once; nine have been infected twice and two have been infected three times.

To eliminate PRRS across the state and the U.S., Dee believes four principles must be in place: The effort must be voluntary, market-driven, and science- and team-based.

“No one is proposing a regulatory program or any restrictions on pig movement,” he says. And that’s the way it should remain.

“The market will drive the establishment of a PRRS-free pig market,” Dee says. Several years ago, demand increased the market for PRRS-free breeding stock and semen. “Right now, infected weaned pigs are refused or discounted on average of $4 per animal. No one will prevent farmers from selling them, but there will be a significant economic disincentive. This will be especially apparent in shareholder-driven cooperatives that operate on weaned pig contracts, as well as pigs crossing the U.S.-Canadian border.”

And to ensure success for the PRRS-free movement, efforts must be science-based and involve a team approach.

Flexible plans

“As new research becomes available, bio-security protocols will be modified and provide a flexible PRRS elimination plan that can be applied to the unique needs of individual farms and regions,” Dee adds. Collaboration among producers, vet clinics and scientists will ensure success.

More research already is needed to help determine how to eliminate PRRS from naturally ventilated barns, which are mainly on finishing barns, Dee says. Sow barns in the state are more likely to be mechanically ventilated.

“We don’t know yet what we’ll do with naturally ventilated facilities,” Dee says. “That might be the next step. If you have pigs coming out of sow barns negative for PRRS, you want to keep them that way.”

On a mission: For most of his professional career — 23 years — veterinarian Scott Dee, University of Minnesota, has worked on projects to eliminate PRRS in producers’ herds.

This article published in the November, 2010 edition of THE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.