A PRRS break and high production costs can destroy an operation.

I have been in veterinary practice more than 20 years. I saw my first case of porcine reproductive and respiratory syndrome (PRRS) in 1997. It is a disease that has caused heartache and significant financial losses for a long time.

We have learned much about the virus in terms of how it is spread, and how to adjust our biosecurity protocols to keep it out. We have gone from not believing it can spread via aerosol methods to thinking it may be the most significant mode of transmission.

We have the technology to genetically sequence the virus and compare the different viruses isolated to see if they are related.

We have both modified live and killed vaccines to help stimulate immunity. We have sophisticated acclimation protocols to insure replacement animals are being exposed to the specific strain of virus in a herd.

We know how to eradicate the virus from a herd and produce negative pigs — only to see the farm break again.

Veterinarians and diagnostic labs have collaborated to geographically map where specific strains of virus are located in order to attempt area control.

With all this said, PRRS continues to be the most significant disease affecting North American pig production today.

When PRRS enters a herd, it can cause such large financial losses that many farms are unable to survive — especially with the large increase in the cost of production.

Case Study No. 1

A 3,200-sow farm with off-site nurseries and finishers has been PRRS positive but is producing PRRS-negative pigs for 18 months. These pigs stayed negative through finishing.

In November 2007, nursery death loss increased. Diagnostics from clinically affected pigs identified PRRS. Within two weeks, we saw clinical signs in the sow barn. Early farrowings had weak pigs, abortions and many sows off feed. We isolated the PRRS virus here as well. When we compared the virus from the nursery to the virus from the sow farm, it was found to be the same virus.

However, this virus was significantly different from any PRRS virus strain previously isolated. We also compared the virus to a large finishing farm less than five miles away without finding any similarities between the two viruses.

This virus caused a large amount of damage. Decreased production and increased costs from this outbreak conservatively raised the cost of production on this sow farm by $5/pig. The added costs in the nursery to finisher phase will easily be $5-$10/pig.

These types of losses are devastating and can't be survived long term.

Case Study No. 2

This 1,500-sow farm has been PRRS positive for many years. Minor flare-ups have occurred, but for the most part have been manageable. With each flare-up we would identify and sequence the virus and find it similar to the previous virus.

However, last fall the clinical disease was much more severe than before, and we isolated a virus that had a considerably different genetic sequence. This is a relatively new sequence that has been showing up across southern Minnesota and northern Iowa. We are cooperating with other veterinarians and the University of Minnesota to evaluate the different geographic areas where this virus has been identified.

To date there has been no clear indication as to where this new PRRS virus originated, or how it was spread.

We have tried intervention techniques to stabilize the sow herd. These efforts have shown good progress, but we still see an occasional problem that is frustrating and costly to deal with.


PRRS transmission studies have shown that contaminated needles, hands, transport trailers, insects, boar semen, shipping boxes and about anything you can possibly imagine as a physical means of transfer of PRRS virus can be a potential source for new virus introduction.

Biosecurity protocols can be put into place to prevent the actual mechanical introduction of the virus into the sow herd.

The one area that has not been widely implemented is the use of virus filters for a barn's incoming air. These filters have been used with success in boar studs, and some sow farms are starting to install them. It appears that a PRRS-negative sow farm in a densely populated area has a difficult time staying negative. There is hope that the filters may keep the virus out of the sow herds. They are expensive — but not as expensive as a PRRS outbreak.

The pork industry needs to work together to continue to look for innovative approaches to controlling and eliminating this costly disease.