Add PCV2 Vaccinations to Pre-breeding Protocols

Boosting antibodies to porcine circovirus type 2 (PCV2) prior to farrowing can help reduce viremia and improve herd productivity.

Porcine circovirus type 2 (PCV2) has been known to affect pigs since 1969 and remains a threat to pork producers across the United States. Widespread use of PCV2 vaccines reduced the prevalence and severity of PCV2 infections. However, genetic shifts in the virus may contribute to the evasion of the vaccine-induced immune responses.

Adding immunization using bivalent PCV2 vaccines can help producers limit their losses and improve their immune response against multiple genotypes, explained Rick Swalla, DVM, head of U.S. Pork Technical Services at Zoetis.

“The virus can actually transmit across the placenta,” he said. “So, we want to get antibodies and cell-mediated immunity as high as we can in the sow herd, so they don’t pass PCV2 on to their piglets.”

Production losses

Previously, the disease resulting from PCV2 infection was known as porcine multisystemic wasting syndrome (PMWS) and is now termed porcine circovirus type 2 disease (PCV2D). PCV2D can cause a range of clinical signs, including:

• Post-weaning diarrhea
• Respiratory dyspnea
• Failure to gain weight
• Respiratory distress
• Tremors
• Enteric disease
• Dermatitis
• Reproductive failure

 

The damage from PCV2 is compounded when combined with other common challenges like porcine parvovirus, porcine reproductive and respiratory syndrome virus (PRRS), Mycoplasma hyopneumoniae, Pasteurella multocida, and Haemophilus parasuis, among others.

“PCV2 is an immune suppressant. PCV2 by itself does not cause a lot of disease, but PRRS, influenza, or Mycoplasma all make PCV2 worse,” Dr. Swalla said. “You can’t give the pigs anything to treat the virus, but you can give other products to treat the clinical signs and help control other diseases.”

PCV2 genotypes

Since PCV2a was identified, there have been two major genotype shifts. Today, PCV2d is most prevalent in the United States. Most traditional vaccines have been targeted at PCV2a.

“Both PCV2b and PCV2d share epitopes. In fact, when PCV2d was identified, it was originally called the mutant PCV2b,” Dr. Swalla explained. “Right now, the predominant genotype is PCV2d, but that will likely change. We’re about to a point where a new one will come along.”

No PCV2 vaccine provides sterilizing immunity; therefore, subclinical PCV2 infections still happen. The significant losses tend to be from co-infection with other viral and bacterial infections.

“We do not have true disease surveillance to tell definitively which genotype is most common,” he said. “The producers that are having problems are the ones sending samples into the diagnostic lab.”

Preventing disease

A recent trial published in Veterinary Research showed a bivalent PCV2a-PCV2b vaccine offered better protection compared to monovalent vaccine including PCV2a alone. Choosing a vaccine with cross-protection is the first step to ensuring producers get the most effective immune response in their herd.

Swalla recommends an early vaccination protocol to help quickly acquire immunity. He typically recommends:

• 1 cc at weaning
• 1 cc about three weeks later

 

For producers challenged with PCV2, Swalla recommends mass vaccination across the entire herd to help boost immune responses. Then, rolling vaccinations can be implemented at weaning and during pre-breeding vaccinations. Not all vaccines are approved for pregnant sows and gilts, which is a critical time to help prevent piglets born already infected with PCV2.

“Pre-breeding is a good time to include vaccinations for lepto, parvo, and erysipelas. A lot of systems have been following this protocol for years, but there are still some operations that don’t believe that every pig needs a vaccine,” he said.

In addition to vaccinations, producers can always benefit from disinfection and biosecurity protocols.

“PCV2 is a hardy virus that lives well in the environment,” Dr. Swalla said. “You can imagine facilities that have had pigs in them for years. There’s just a lot of this virus in the environment.”

 

Key Points

• PCV2-infection is widespread — essentially, all pig herds are infected with PCV2.1
• PCV2-associated disease (PCVAD) includes respiratory and reproductive challenges.1
• Pigs that show signs of PCV2 systemic disease are usually infected with multiple agents, including parvovirus, including porcine parvovirus, porcine reproductive and respiratory syndrome virus (PRRS), Mycoplasma hyopneumoniae, Pasteurella multocida, and Haemophilus parasuis, among others.

 

1 Iowa State University. Porcine Circovirus Type 2. Accessed Dec. 6, 2022. Available at: vetmed.iastate.edu/vdpam/research/disease-topics/swine/pcv2

 

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