It’s been nearly 15 years since the “Mystery Disease”, as it was first called, reared its ugly head on U.S. swine farms. Porcine Reproductive and Respiratory Syndrome, as it’s now known, has since become the industry’s most frustrating and devastating disease. Working estimates suggest it costs the industry about $600 million annually.

Any producer who has dealt or is dealing with PRRS knows all too intimately about the virus’ ruthlessness.

While there hasn’t been a shortage of research or effort aimed at the disease, either in the United States or worldwide, there has been a lack of focus, and some would argue, cooperation.

In an attempt to change that, the National Pork Board’s Swine Health Committee has instructed “us to build a program to give pork producers the tools they need to fight this disease,” says Eric Neumann, DVM, NPB’s director of swine health information and research. “Our (NPB) job is to act as a consensus-building body; help break down barriers and get researchers to talk and work with each other.”

The result is a 13-point plan, which will involve producers, veterinarians, universities, researchers, government agencies and allied industry.

“The goal is to take short-term and long-term approaches to solving the PRRS puzzle,” says David Culbertson, an Illinois pork producer who serves on NPB’s swine health committee. “A national, unified effort is necessary.”

“Fighting PRRS will take more funding and more long-term research projects,” points out Neumann. In total, the national initiative could take “10 to 15 years,” he adds.

Here are the details of NPB’s national PRRS initiative:

  • Quantifying the Cost of PRRS: Any producer that has experienced an outbreak will attest to PRRS’ economic significance on his or her operation. A thorough assessment of PRRS’ cost to the U.S. pork industry will support the financial commitment needed to complete the objectives outlined in this initiative.
  • Publication and Distribution of 2003 PRRS Compendiums: NPB published the first comprehensive review of the scientific literature on PRRS in 1998. Two updated volumes of the compendium is now complete. One is known as the “Second Edition”, which is targeted toward PRRS researchers and veterinarians. The “Producer Edition” is an abridged version that provides a practical format for producers to use. A CD-Rom, which includes both versions also is available. (For purchasing information, go to or call (800) 456-PORK.)
  • Cooperative Vaccine Development: Only limited vaccine choices are available today. New and novel candidate vaccines can be helpful in PRRS-control programs, and further development is needed.
  • Understanding the Persistently Infected Pig: PRRS virus is notable for its ability to develop long-term, persistent infections that complicate control and elimination programs. Understanding the mechanisms and developing testing strategies to identify persistently infected hogs is critical.
  • Immune Therapy: Antiviral compounds and immune therapies have proven useful for numerous diseases. The application to PRRS has not been fully investigated, but may prove helpful in disease management.
  • PRRS Virus “Typing” Systems: The virus has a remarkable ability to mutate into new strains. Devising a system to categorize newly evolved strains into similar “families” will facilitate vaccine development and regional PRRS-elimination programs.
  • PRRS Virus Genomic Sequencing, and a National Database: Mounds of diagnostic information about PRRS outbreaks and characteristics of the specific virus strains already exists. However, the data has not been collected and stored in a manner that allows researchers to fully analyze the outbreaks. Developing a national database will allow strains to be catalogued and ensure that data from new outbreaks can be effectively analyzed.
  • National Epidemiologic Investigations and Risk-Factor Analysis: Not all of the factors that put a farm at risk have been defined. Large-scale, national epidemiologic analysis will provide useful information in designing on-farm and regional PRRS elimination programs.
  • Mechanisms of Between-Farm Transmission: There is strong anecdotal evidence that PRRS virus can move between farms. The mechanisms and relative importance of inter-farm transmission still need to be understood.
  • Regional PRRS-Elimination-Demonstration Projects: Some strategies are available to eliminate PRRS virus from well-managed and geographically isolated farms. However, eliminating the virus from a large geographical region is necessary to protect PRRS-negative farms from re-infection. Regional PRRS-elimination projects will provide the information to develop sustainable control programs.
  • Engaging International PRRS Researchers: PRRS is a worldwide disease. Familiarity with research around the globe will speed development of management solutions that could apply to the United States.
  • Collaborate with Researchers of Related (non-swine) Viruses: Viruses related to PRRS exist in other species. Familiarity with those diseases and researchers who study them can lead to more fully understanding PRRS.
  • Develop of a Real-Time PRRS Information and Education System: A real-time system to disseminate updates and information to producers and veterinarians will be developed.

NPB staff and the Swine Health Committee are working to develop a detailed plan for each of the 13 objectives.

Neumann projects the initiative’s total cost could run $10 million to $15 million, but that’s not just checkoff funding.

“We’re talking to USDA to ensure that they understand the need to address this disease, and its financial impact,” says Beth Lautner, DVM, and NPB’s vice president of science and technology. She points out that there are government grants that may be available for the program. 

“This initiative highlights the need for a sustained focus on PRRS,” says Neumann. “It will take the commitment of numerous funding sources, dedicated researchers, swine veterinarians and the pork checkoff to see it to its successful conclusion.” 

Why Such a Challenge?

There are several explanations for the difficulty of controlling PRRS virus infections. Eric Nuemann, DVM, with the National Pork Board, offers these perspectives.

First, PRRS virus is a positive-stranded RNA virus, highly prone to mutation. Virus mutation creates strains with unique antigenic profiles that can result in poor cross-protective immunity in infected pigs. This makes vaccine development particularly challenging. Additionally, complicated clinical disease episodes can result when a herd has more than one virus strain or faces sequential new infections by different strains.

Second, PRRS virus seems to elicit a complicated and unique immune response, which has hindered vaccine development, as well as management and elimination strategies. The virus also has the ability to persist, thereby re-infecting hogs.

Third, anecdotal evidence strongly suggests that the virus can move between farms. The relative importance of aerosol transmission, biologic vectors and physical vectors can only be speculated on at this time. Many have reported outbreaks despite stringent biosecurity and defined PRRS-control strategies.

Finally, the fact that relatively few tools including vaccines are available to producers and veterinarians to manage the disease only compounds the challenges. Attempts to manage PRRS through pig flow, gilt management, biosecurity and multi-site production has not offered predictable, sustained control.