Trials show circovirus vaccines are producing marked reductions in finishing mortality, boosting pig performance and percentages of hogs marketed.

Circovirus vaccines are performing as advertised — producing dramatic improvements in swine health, adding hogs and pounds of pork on the market.

With pork production surging, the question now is whether those improvements will eventually flood the market and drag down hog profitability. It's expected that hogs marketed in the fourth quarter of 2007 will exceed numbers produced in that fatal period in 1998, when reduced slaughter capacity, coupled with record pork production, led to single-digit hog prices.

This time around, slaughter capacity is in much better shape, but production of the three commercially available circovirus vaccines has yet to hit its peak. Those vaccines include Suvaxyn PCV2-One Dose from Fort Dodge Animal Health, Ingelvac CircoFLEX from Boehringer Ingelheim Vetmedica, Inc. (BIVI) and Porcine Circovirus Vaccine Type 2 from Intervet Inc.

Fort Dodge Animal Health, for instance, indicated at World Pork Expo that while supplies in the pipeline are growing, peak production of their vaccine would not occur until well into the third or fourth quarter of this year.

“Most of us would agree that this disease did have an impact on slaughter weights and mortality, which did offset some of the increases in sow productivity that is occurring on farms over the last 18 months,” observes Joe Connor, DVM, senior swine consultant at Carthage (IL) Veterinary Services, Ltd.

“The industry has not had enough vaccine available to impact the market yet. But for the fourth quarter of 2007 forward, I believe we will have enough vaccine available to increase the percentage and pounds of pigs marketed,” he adds.

Results Encouraging

Connor reported on several trials with the Fort Dodge vaccine, noting it has protected against all of the strains of the disease known as porcine circovirus-associated disease (PCVAD), including both the American and European strains.

While cases of PCVAD have returned mostly to endemic (subclinical) levels in Europe, many U.S. herds are still experiencing epidemic losses, he reports.

Reviewing losses due to PCVAD in nine wean-to-finish production systems in Illinois points out that the syndrome has had a big impact on cost of production in terms of marketable pigs, says Connor. Figure 1 shows vaccination has helped groups reach nearly 98% marketable pigs, compared to about 92% for nonvaccinated groups.

Figuring into that equation is mortality rates (Figure 2), which average 6.5% or higher for unvaccinated groups vs. 3% or less for vaccinated pigs.

In another large study, wean-to-finish death loss was more dramatically altered, going from 9.2% in nonvaccinates to 3.09% for pigs inoculated with the Fort Dodge PCV2 vaccine, Connor notes.

The vaccine trials also produced an improvement in average daily gain from 1.5-1.6 or under for nonvaccinates to 1.7 or higher for vaccinates, he says.

Similarly, feed conversion advanced from 2.40-2.45 for nonvaccinates to around 2.35 for vaccinates.

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Vaccine Timing Critical

The Fort Dodge vaccine is licensed for use in pigs 4 weeks of age and older. Connor stresses for vaccine efficacy, however, it is important to get ahead of PCV2 infection.

To that end, there is a movement to vaccinate pigs younger, at 1-3 weeks of age, under veterinary direction, which also helps get ahead of co-infections such as porcine reproductive and respiratory syndrome (PRRS) that occur in the nursery, he states.

By vaccinating pigs earlier, it is possible to vaccinate “through maternal antibody” to protect younger piglets from disease, and still provide an adequate duration of immunity through finishing, Connor explains.

Clinical Picture of PCVAD

Most cases of PCV2 typically occur 2-4 weeks into the finisher phase. During the following 2-3-week time period, affected pigs drastically lose weight and dramatically fall behind penmates.

Connor says in the last 12 months, there have been some field reports of sow herds being affected, aborted fetuses and weak-born piglets. Some reports indicate vaccinating sows have dramatically lowered the impact of disease, but field trials need to be completed to determine the impact of PCV2 on reproductive performance.

Ileitis-type diarrhea is also a definite part of the circovirus syndrome that has gone largely undetected until recently.

Vaccine Not a Cure-All

Connor says vaccine alone won't stop circovirus, so producers must manage co-infections and work on pig flow.

“A lot of data from 2-3 years ago shows that poor pig flows, poorly ventilated barns and barns that don't get dry have a much higher rate of failure, of clinical outbreaks of PCVAD,” he says.

Individual animal therapy hasn't been cost effective when it comes to managing pigs infected with PCVAD. The best strategy has been to remove sick pigs from the barn to treat them elsewhere or euthanize them, he adds.

With limited vaccine availability in the last year, Connor says the strategy has been to intervene with vaccine in the most serious problem flows and work on improving management in other affected pig flows to minimize losses.

Biosecurity Overhaul Needed

Biosecurity systems in the United States today are not adequate to keep out porcine circovirus, charges R.B. “Butch” Baker, DVM, Iowa State University (ISU).

While at North Carolina State University's College of Veterinary Medicine, Baker investigated a major outbreak of circovirus in one of the higher-health systems in the state. The sow farm was PRRS-stable, had few problems with Mycoplasmal pneumonia and little respiratory disease. Although the pigs from this system were PCV2-positive, no wasting or mortality syndrome originally existed.

“Something changed and this previously highly productive system developed severe PCVAD. This farm had averaged approximately 4.5% mortality from wean to slaughter the previous year, but once PCVAD started, some of the finishing barns suffered high mortalities, occasionally greater than 30%; one was even more than 50%, and the site I visited had 53% mortality,” Baker says.

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Prior to his academic role, Baker worked with a large integrator that had one of the best biosecurity systems of any commercial farm in the United States. While there, he helped develop the Trailer Baker, which dries trailers for 10 minutes at 165-180° F.

“We validated that we could easily kill TGE (transmissible gastroenteritis) virus, PRRS virus, most of the salmonellas and E. coli by heating these trailers in an insulated bay.

“But recent research indicates that you are not going to completely destroy PCV2 virus by heating trailers to 248° F for 30 minutes with dry heat. This would be impractical because of cost and damage to both trailers and tractors. It appears that we would only get a small reduction in the amount of the virus even at these temperatures,” he says. Circovirus managed to slip through the trailer heating and all the biosecurity measures at this integrator.

“So our trailer dryers are not effective in preventing transmission of this virus. Steam heating at 110-120° F does a lot better job, but even 30 minutes of wet heat probably won't kill all virus left behind in our trailers,” Baker says.

There are several disinfectants that do a good job destroying the virus, but “the problem is you just can't disinfect everything on a pig hauling trailer,” he says.

Circovirus is a very hardy virus, which is “ubiquitous or everywhere in pig populations. I suspect it can easily be tracked around the world,” Baker says. The virus is likely spread through fecal-oral contact and contaminated fomites. Airborne transmission doesn't appear to be a likely means of spread.

To prevent new diseases from periodically spreading through the swine industry, biosecurity systems will need to be overhauled, he suggests.

PCVAD Co-Infections

Baker says ISU has diagnosed more than 1,000 field cases of PCVAD in their Veterinary Diagnostic Laboratory at Ames so far this year. In a subset study of 454 cases during 2006, only nine were PCV2 alone. A third of the cases were PCV2 and PRRS virus; 92 were PCV2, swine influenza virus (SIV) and mycoplasma; 77 were PCV2, PRRS and SIV, and 68 were PCV2 and mycoplasma.

In a recent on-farm survey of 60 U.S. herds, conducted by BIVI and ISU, 72% of the PCVAD cases also had coexisting PRRS. Salmonella was found as a co-factor in 58% of the cases. SIV and mycoplasma were identified as concurrent infections with PCVAD in 30% and 18% of the cases, respectively.

The results are based on findings from the MAGIC (Monitoring Assignment for Global Insight of Circovirus) diagnostic trials that were conducted by BIVI in 2006 in an effort to improve understanding of PCVAD and the role of co-infections.

The MAGIC project includes herd history, mortality rates, PCVAD symptoms and individual animal diagnostics. All samples were evaluated by ISU's diagnostic lab.

Those studies revealed that co-infections usually produced higher levels of disease and lesions than with PCVAD infection alone.

An ISU study also showed that PCV2-infected pigs that were vaccinated for PRRS had significantly increased average daily gain and fewer lung lesions over non-PRRS vaccinated, PCV2-infected pigs.

“The research shows just how important it is to control PCV2, PRRS, salmonella and other diseases as a way to reduce or mitigate the severity of PCVAD where it's a problem,” says John Kolb, DVM, BIVI. “Especially in regards to PRRS, the combination of PRRS and PCV2 can be most devastating to a production system.” More information is at www.bi-vetmedica.com or 800-325-9167.

Reference Sources

Fort Dodge Animal Health (FDAH) announced at World Pork Expo that it is pursuing two efforts to expand the knowledge base about circovirus, according to Craig Wallace, vice president of marketing for FDAH.

In July, the company is launching a Web site called www.stopcirco.com to serve as a technical reference source. “We want it to be the place where people can go for the latest information about circovirus,” he says. It will link to a company site called Swine Health Solutions.

FDAH has also started a Risk Assessment database. The eventual goal is to have universities, veterinarians and producers providing information into the database to pinpoint the factors that most commonly lead to circovirus outbreaks.

“We believe that this will help us do a better job of managing this disease and use techniques for prevention,” he explains.

Learn more by calling 800-685-5656 or logging onto the circovirus Web site.

Intervet Vaccine Proves Effective

Intervet's conditionally licensed vaccine showed effectiveness in reducing mortality and clinical signs from porcine circovirus-associated disease (PCVAD).

Rich Schlueter, DVM, Intervet Swine Technical Services, reported results on Porcine Circovirus Type 2 during a World Pork Expo educational seminar. The killed-virus, two-dose vaccine is approved for use in pigs 3 weeks of age and older.

In company-conducted laboratory studies, nasal shedding and fecal shedding were both eliminated in pigs vaccinated and then challenged with the virus compared to controls, which readily shed the virus over the 42-day observation period.

In one field study conducted in multiple barns, overall mortality from PCVAD was reduced from 15.2% for nonvaccinates to 5.5% for vaccinates.

In three other field evaluations:

  • Field evaluation No. 1 — 1,149 vaccinated pigs were placed on test vs. 1,229 nonvaccinates. Pigs were fed to a market weight average of 289 lb. for vaccinates vs. 274 lb. for nonvaccinates, returning $22.90/head for vaccinates vs. $10.46 for nonvaccinates, based on a live market price of $47.70/cwt. Death loss was dramatically different — 2% for vaccinates vs. 14.4% for nonvaccinates.

  • Field evaluation No. 2 — 1,252 head were vaccinated vs. 1,224 head unvaccinated. About 5.10% of vaccinated pigs died vs. 8.74% of nonvaccinated pigs. In addition, the cull rate for vaccinates vs. nonvaccinates was 0.24% vs. 9.07%, respectively.

  • Field evaluation No. 3 — Pigs were vaccinated five weeks after being moved into a finisher, next to a group of nonvaccinates. Some 1.1% of vaccinates were culled, compared to 7.5% of nonvaccinates. Final mortality was 3.2% for vaccinates vs. 12.4% for nonvaccinates.

Schlueter also provided results from a Canadian field study involving PCVAD-infected herds in Quebec and Ontario. Collectively, the herds had mortality rates of 10.45%. When immunized with the Intervet vaccine, mortality dropped to 2.76%.

Schlueter says Intervet's PCV2 vaccine “has been highly effective in reducing mortality in severely affected herds.”

He recommends vaccinating pigs early (3 weeks of age, per label directions) to provide optimum protection before the disease takes hold. Vaccination interference from maternal passive antibodies apparently is not an issue with early vaccination.

Consider other strategies if pigs are infected at a young age.