Preliminary Trials for a PCV2 Swine Vaccine Look Promising

KANSAS - Kansas State University researchers have developed what appears to be a promising vaccine against Porcine Circovirus Type 2 (PCV2), a disease that researchers predict every swine herd in the United States is infected with.
calendar icon 15 February 2007
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PCV2 depletes the lymph node system so that the hog’s body can’t defend itself against other pathogens, which is why many pigs infected with the disease die. Some symptoms include 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 it. The virus has been reported to be excreted through nasal and ocular secretions, urine, feces, colostrum and semen.

In a recently completed study of the vaccine, researchers found that pigs that received the vaccine showed significant reductions in mortality, increased growth rate during the finisher pig stage and fewer light weight pigs at market, said Dr. Steve Dritz, Kansas State University Research and Extension swine specialist.

K-State researchers, Bob Rowland, Dick Hesse, Steve Dritz, Jerome Nietfeld and Kyle Horlen, conducted the wean-to-finish clinical trial on a commercial hog farm in northeast Kansas using 485 pigs. The pigs were randomly divided into six groups at the time they were weaned and were given doses of the vaccine at three and six weeks of age, said Dritz who is a swine specialist for the K-State College of Veterinary Medicine. Some mortality rate prior to the trial had been as high as 20 percent.

The trial results showed that in the finisher phase, the mortality rate for vaccinated pigs was 50 percent less than for unvaccinated pigs and that the growth rate for vaccinated pigs increased 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 study of the vaccine in a commercial research finishing barn, mortality, growth rate and feed efficiency improvements were calculated to result in a benefit of $3.94 per pig.

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 effectiveness of the vaccine, this study really highlights the devastating impact that infection with this virus can have on swine production,” Dritz said. “Results from this study suggest that the vaccine will be an effective tool in controlling the disease in pigs caused by Porcine Circovirus Type 2.”

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

“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 said. “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 molecular characteristics of the virus and to develop diagnostic tools, Dritz said. The 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.

The researchers, who are all on faculty at K-State’s College of Veterinary Medicine, collaborated on the study with partial funding provided by the National Pork Board.

A PCV2 vaccine for use in sows and gilts has been available in France and Germany for about two years, Dritz said. In one study from France, the average weaning to slaughter mortality rate of offspring dropped from 11.0 to 7.7 percent in 15 herds where the vaccine was used. German studies used 38 herds and found that the birth to slaughter mortality rate dropped from 28.7 to 17.9 percent in groups where the vaccine was used.

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