A federally licensed vaccine for porcine circovirus provided excellent results in recent trials.
Last June, a team of Kansas State University (KSU) swine researchers was searching for the right commercial herd to test a federally licensed circovirus vaccine. The goal was to determine vaccine efficacy and provide some hope to frustrated producers in the state.
An isolated, 300-sow, farrow-to-finish operation in northeast Kansas fit the bill. The family-owned operation had a recent history of severe porcine circovirus — and it was negative for porcine reproductive and respiratory syndrome (PRRS), says KSU's project leader Bob Rowland, a virologist and associate professor of diagnostic medicine and pathobiology.
Another key factor in selecting this farm for vaccination was because it was infected with a different strain of the virus known as PCV2B. The strain that nearly all pigs in the United States carry, which is perhaps less pathogenic, is known as PCV2A.
Overall, vaccinated pigs demonstrated significant reductions in mortality, dramatically increased growth rate during finishing and fewer lightweight market hogs, explains Steve Dritz, DVM, KSU Research and Extension swine specialist.
The KSU team of Rowland, Dritz, Dick Hesse, Jerome Nietfeld and Kyle Horlen conducted the wean-to-finish trial on 485 pigs, randomly divided into six groups at weaning. Pigs were vaccinated at 3 weeks of age (weaning), and a second dose was given three weeks later, according to label directions.
Results were impressive, adds Rowland. In the finisher phase, the mortality rate for vaccinated pigs was 50% less than for their unvaccinated counterparts. Mortality was 7% for vaccinated pigs, compared to 17% for non-vaccinated pigs. Vaccinated pigs grew about 10% faster.
“Results from this study suggest that the tested vaccine is effective in controlling porcine circovirus type 2-associated disease in pigs,” he says. The USDA-licensed vaccine offers safety and efficacy.
“In addition to demonstrating the effectiveness of this vaccine, this study really highlights the devastating impact the infection with this virus can have on swine production,” Dritz says.
Disease transmission of porcine circovirus has been especially troublesome, reports Steve Henry, swine veterinarian from Abilene, and an adjunct professor of diagnostic medicine and pathobiology at KSU who is working closely with the research team. He said disease outbreaks have occurred rapidly, yet randomly, in hog operations with the highest levels of biosecurity.
“The ineffectiveness of biosecurity makes control strategies like quarantine practically irrelevant if the virus can bypass the barriers,” Henry notes. “With porcine circovirus, we are not experiencing classic disease outbreaks, in which the initial occurrence is followed by the ripple effect, spreading out from a source point.”
“We've worked with herds operating with very high biosecurity and it has just not slowed this virus down,” Rowland adds.
While the KSU trials show the effectiveness of the commercial vaccine, product availability remains a question mark, Dritz comments.
Henry adds: “Federally approved vaccine supplies have been totally inadequate thus far, with little or no supply in the face of an acute national problem.”
“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 continues. “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.”
Also underway is the development of diagnostic tools to help characterize the virus to aid in the investigation of how it spreads from herd to herd, or how the infection develops into severe forms of the disease, he says.
Circovirus is shed through nasal and oral secretions, urine, feces, colostrum and semen. Symptoms of disease include rapid weight loss, lethargy, anorexia or loss of appetite, skin discolorations or lesions, respiratory problems and diarrhea.
A next-generation diagnostic test would help not only in timing of vaccination, but also in establishing prevalence of specific strains of circovirus in Kansas herds, adds Rowland.
Financial support is being provided by the National Pork Board and affected Kansas pork producers.