Kansas State University researchers have evaluated what appears to be a promising vaccine against porcine circovirus Type 2, a virus that researchers predict infects every swine herd in the United States.

PCV2 depletes the lymph-node system so that the hog´s body can´t defend itself against other pathogens. It is the base for the recent evolution of porcine circovirus associated disease, which includes symptoms such as anorexia, rapid weight loss, generally unhealthy pigs, skin discoloration or lesions, respiratory problems and diarrhea. However, not all hogs infected with PCV2 show signs of PCVAD. While much remains unknown about PCVAD, some expectations are that PCV2 can be excreted through nasal and ocular secretions, urine, feces, colostrum and semen.

In a recent study, researchers found that pigs receiving the vaccine showed significant declines in mortality, increased growth rate during the finishing-pig stage and fewer light weight pigs at market, says Steve Dritz, Kansas State University Research and Extension swine specialist.
Kansas State researchers conducted wean-to-finish clinical trials on a commercial hog farm in northeast Kansas using 485 pigs. The pigs were randomly divided into six groups at weaning and were vaccinate at three and six weeks of age. Some mortality rates prior to the trial had been as high as 20 percent.

The trial showed that in the finishing-phase, the mortality rate for vaccinated pigs was 50 percent less than for unvaccinated pigs. As for growth rate, the vaccinated pigs improved by about 10 percent. Results also showed that the average market weight for vaccinated pigs was about 20 pounds heavier for the same number of days to market when compared to unvaccinated pigs.
In a separate vaccine study in a commercial research finishing barn, mortality, growth rate and feed efficiency improvements were calculated at $3.94-per-pig benefit.

Mortality associated with PCV2 was first described in Canada in the mid 1990s. The virus has been a significant disease affecting pigs in Europe for the last 10 years. However, it has only recently become a major problem in the United States.

"In addition to demonstrating the vaccine's effectiveness, this study highlights the devastating impact this virus can have on swine production," Dritz says. "Results from this study suggest that the vaccine will be an effective tool in controlling the disease in pigs caused by PCV2."

Researchers are unsure, however, when the vaccine will be available for producer use.

"The next steps are to continue to evaluate the vaccine under different field conditions to ensure that it is broadly applicable across the industry," Dritz says. "We´re looking for more herds that have a less significant rise in mortality, but do have infection with the virus to see if it is still economical to vaccinate."

Research also still needs to be done to further evaluate the virus' molecular characteristics, and to develop diagnostic tools, he adds. Diagnostic tools will aid in the investigation of how the virus spreads from herd to herd or how the infection develops into severe forms of the disease.

Source: Kansas State University