PRRS Research Results Trickle In

Almost $2 million has been spent by the National Pork Board in each of three years of funding the PRRS research initiative. The National Pork Board has put out a call for projects for a third year to fund porcine reproductive and respiratory syndrome (PRRS) research. Additionally, the board is announcing the first round of results from 12 projects funded in 2004. A total of 49 projects have been funded

Almost $2 million has been spent by the National Pork Board in each of three years of funding the PRRS research initiative.

The National Pork Board has put out a call for projects for a third year to fund porcine reproductive and respiratory syndrome (PRRS) research. Additionally, the board is announcing the first round of results from 12 projects funded in 2004. A total of 49 projects have been funded to date. Details can be found at

Why does it seem to take so long to get research results?

There are practical and logistical reasons, says Pam Zaabel, DVM, director of Swine Health Information and Research for the National Pork Board.

For starters, although the first-year call for PRRS research project funding went out in March 2004, those projects weren't actually funded until 4-7 months later. “If you had a 12- to 18-month project, that pushes some of those results up to the first of this year,” she explains.

Second, it's fairly common to grant time extensions to complete research projects — and PRRS is certainly no exception. Pigs don't get sick when they are supposed to, or buildings don't become available, so projects sometimes get off schedule.

Availability of reagents and equipment malfunctions can also delay results. Plus, some PRRS research projects are fairly complex, raising more questions to address, thus extending the length of the trial, says Zaabel.

The adjoining pie chart (Figure 1) illustrates the division of resources for research projects that focus on three areas: PRRS vaccination, elimination and persistent infection. Twelve completed projects in those three areas include:

PRRS Vaccination: University of Nebraska researchers studied development of a new generation of PRRS virus differential (marker) vaccines. In doing so, they have identified genes that help the PRRS virus invade and infect the pig. Producing copies of the virus (with these genes removed) may lead to the development of a vaccine that will stimulate protection and not cause disease.

Washington State University scientists developed new cell lines that are susceptible to PRRS virus infection that, with further research, may be used for vaccine production. (The only cell line that exists for vaccine production is patented.)

Iowa State University researchers have developed a killed subunit PRRS vaccine. When the vaccine was given, the pig's immune system produced a small amount of antibody. If produced in larger amounts, the vaccine would hold the potential of stopping infection.

At the University of Minnesota, scientists collaborating with ATG Laboratories produced large quantities of purified PRRS viral proteins to be available to researchers at no cost for a variety of testing procedures.

Iowa State University workers developed anti-PRRS virus neutralizing antibodies to clear the virus from a cell line. This could potentially be developed into a marker vaccine.

Persistent Infection: These pigs are carriers of the PRRS virus and shed it without showing signs of disease, Zaabel explains.

At the National Animal Disease Center in Ames, IA, scientists are studying the interaction of PRRS virus and porcine dendritic cells as playing a potential role in viral persistence. They have isolated a specific type of white blood cell (a dendritic cell) in pig lungs that may help sequester the virus and transport it to the lymph nodes where it may persist.

A dye tested unsuccessfully tracked the movement of dendritic cells throughout the body.

University of Missouri tests determined that PRRS virus may persist in tonsilar fluid for 160 days after exposure following a modified-live-virus vaccine or a live PRRS virus inoculation.

The researchers also developed a scraping method to collect samples of tonsilar fluid from live pigs to test for PRRS.

South Dakota State University and Kansas State University researchers jointly studied the emergence of European-like PRRS virus in the United States. They found that the European-like PRRS virus, similar to its U.S. counterparts, would continue to change genetically.

The group also compiled an extensive reference panel of pig sera to be used by diagnostic laboratories to test for European-like isolates of PRRS.

PRRS Elimination: Scientists at Iowa State University constructed models of chambers to predict aerosol transmission.

University of Minnesota researchers assessed vertical transmission from Parity 1 sows infected with a low-dose, mild strain of PRRS and found:

  • When sows were exposed at 90 days of gestation to PRRS virus, the amount of virus didn't affect the number of piglets shedding at birth or the amount of virus in serum.

  • Four days of age is the best sampling age compared to birth or weaning;

  • Any farrowing of an acutely affected herd can be sampled because the number of pigs infected and the amount of virus does not vary in positive pigs; and

  • Litters infected with PRRS virus have lower growth performance during lactation.

Researchers at the University of Minnesota are testing a pilot project to determine the feasibility of controlling PRRS within a region. So far, producers are sharing PRRS status and control experiences.

The Swine Vet Center of St. Peter, MN, has sampled boars for early infection of PRRS virus using a new serum collection technique that involves puncture of the ear vein prior to semen collection using a blood swab.

This technique has proven to be less stressful for the boars and less dangerous for staff, says Zaabel. Blood swab sampling should replace semen sampling for boar studs.

Pork Board Session

On Sept. 24, during the Leman Swine Conference, the National Pork Board will offer an update on the PRRS, environmental, animal science, pork safety and animal welfare projects they've funded, says Zaabel.

These presentations will contain information that can be directly applied to production units. Producers and swine veterinarians can obtain further information by contacting Zaabel at the Pork Board at (515) 223-2600.

Collaboration Advances PRRS Research Efforts

It takes a lot of teamwork in research at universities and government laboratories around the country and abroad to make progress in eliminating porcine reproductive and respiratory syndrome (PRRS), according to Bob Rowland, Department of Diagnostic Medicine/Pathobiology at Kansas State University.

Rowland chairs NC-229, which brings together basic and applied scientists to envision how research translates to the field. The goal is to help producers struggling with PRRS in their operations.

NC-229 was established in October 1999 under the guidance of PRRS researcher David Benfield of Ohio State University. The North Central Regional Association of Agricultural Experiment Station directors initiated the effort, targeting the detection, protection and elimination of PRRS virus, with select universities and the U.S. Department of Agriculture's (USDA) Agricultural Research Service laboratories forming the core of PRRS research.

A crowning achievement for NC-229 was the development of the International PRRS Symposium, formally launched in 1999. This meeting grew out of annual research reports given by NC-229 researchers. The annual program is free to the public and is held just prior to the Conference of Research Workers in Animal Diseases (see separate story).

The collaborative nature amongst researchers led to formation of PRRS CAP-1, the first Cooperative Agricultural Project on PRRS, a four-year program funded at $4.4 million by USDA, under the direction of Michael Murtaugh of the University of Minnesota.

This multi-disciplinary, multi-institutional team approach bridges the gap in research, Extension and education on PRRS, while reducing duplication and fostering collaboration, says Rowland.

The PRRS-CAP group attempts to address “outside the box” research ideas as well as help provide a training ground for future leaders in PRRS research, he adds.

PRRS CAP-1 specifically looked at biosecurity within herds, viral spread within herds, diagnostics and monitoring, and regional elimination of the virus from the boar stud and genetic replacements, to the breeding farm and growing pig.

PRRS CAP-2 provides a continuation of the four-year project, funded by USDA at $4.4 million. The project is under the direction of new project leader Rowland.

Specific PRRS-CAP-2 research efforts will focus on:

  • PRRS vaccines: The goal is to develop a vaccine to protect a herd in which the virus has been cleared to prevent reinfection, he says.

  • Immunology: “We still don't understand how the virus interacts with the pig,” points out Rowland.

  • PRRS ecology: “People still don't understand how PRRS gets on the farm, and once it gets in, how does it circulate? Can we find ways to cut it off once it gets in?” he asks.

“Our job is to develop the scientific tools for the control and elimination of PRRS,” Rowland notes.

After PRRS CAP-2 ends, so does USDA funding. Thus, the pork industry should support PRRS CAP-2 and make PRRS elimination a reality, he adds.

International PRRS Meeting

PRRS Eradication — Is It Possible?

That's the theme for the 2006 International PRRS Symposium to be held Dec. 1-2 in Chicago, IL.

This annual public meeting is held prior to the Conference of Research Workers in Animal Diseases. Site of both meetings is the Chicago Marriott Hotel-Downtown (312/836-0100 or 800/228-9290).

A broad range of topics is planned, from field studies to highly technical investigations. Discussions include PRRS diagnostics, persistence and genetic resistance.

Reports will cover PRRS CAP-1 summaries and details of the PRRS research initiative from the National Pork Board. Major epidemiological factors controlling virus spread, elimination and eradication will be addressed.

Organizers are currently soliciting scientific abstracts for presentations and poster displays (deadline is Sept. 8).

There is no charge to attend, but registration is required through the symposium Web site,

For more information, contact conference chairman Bob Rowland at or co-chairs Joan Lunney at jlunney@anri.basc.usda or Pam Zaabel, DVM, at