Sign up now!
Don't show this again
Sweepstakes Rules
Download the report!Continue to Site >
or wait 7 secs

Thank you for confirming your subscription!

(And remember, if ever you want to change your email preferences or unsubscribe, just click on the links at the bottom of any email.)

We’re glad you’re enjoying Pig Health Today.
Access is free but you’ll need to register to view more content.
Already registered? Sign In
Tap to download the app


Collect articles and features into your own report to read later, print or share with others

Create a New Report


Read Later

Create a new report

Report title (required) Brief description (optional)
follow us

You must be logged in to edit your profile.

Favorites Read Later My Reports PHT Special Reports
Pig Health Today is equipped with some amazing (and free) tools for organizing and sharing content, as well as creating your own magazines and special reports. To access them, please register today.
Sponsored by Zoetis

Pig Health Today | Sponsored by Zoetis


Rate of PCV2 recombination not widely recognized

An interview with
Meggan Bandrick, DVM, PhD
Associate Director
Global Biologics Research


Download the pdf

Q: Recombination of porcine circovirus type 2 (PCV2) is a known phenomenon in the  research arena. Is there awareness of PCV2 recombination in the field?

MB: In the field we’re finding awareness of recombination, but the extent of recombination isn’t fully realized.


Q: What is the rate of PCV2 recombination?

MB: In one study of PCV2 viruses, 33% of 898 sequences from 32 countries were found to be PCV2 recombinants.1 In another, smaller study, the percentage of PCV2 recombinants was a similar 34%.2


Q: How does the rate of PCV2 recombination compare with other viruses that  affect swine? 

MB: As an example, let’s consider influenza viruses, for which recombination is generally considered to be rare.3  In a study of 3,815 human and swine influenza virus gene segments, only 1% were recombinants.4 From what we’ve seen, PCV2 recombination appears to occur at a much higher rate compared to flu viruses. I should note that flu viruses are able to  reassort, but PCV2 viruses cannot.


Q: How does recombination occur and how does that differ from reassortment?

MB: Recombination occurs when two or more PCV2 viruses infect the same single cell.  Say you’ve got PCV2a and PCV2d in the same cell. They swap genetic material and you get  a recombinant — a child with genetic bits of both parent viruses.

Reassortment occurs when segments of a virus genome are exchanged. PCV2 doesn’t have a segmented genome and that’s why it can’t reassort. Influenza viruses can reassort because their genomes are segmented.


Q: What PCV2 strains are found in recombinants?

MB: They’re usually commonly circulating PCV2 viruses — PCV2a, PCV2b and PCV2d, which is the most predominant PCV2 strain now in the US.5


Q: But do the recombinants cause clinical disease?

MB: It appears so. In one study, PCV2a/PCV2d recombinants were in samples from pigs with wasting, characteristic of PCV2 disease.6 In another study with PCV2a/PCV2b recombinants, samples were from diseased and dead pigs.7


Q: Do commonly used diagnostic tests identify PCV2 recombinants?

MB: Currently they don’t. The technology needed to identify recombinants is still primarily limited to research facilities.


Q: Most PCV2 vaccines are based on PCV2a. They’ve provided some cross-protection against other genotypes, but do they protect against recombinants?

MB: Not necessarily. Vaccine failures associated with antigenic changes in PCV2 have been reported.8,9,10 Seemingly minor variations in the capsid protein — the virus part recognized by the immune system — can allow some of the new PCV2 viruses to escape the pig’s response to vaccination.11

Let’s say a pig has a PCV2a/PCV2b or PCV2a/PCV2d recombinant virus and has received a PCV2a vaccine. The immune system will recognize the PCV2a capsid but may not fully recognize PCV2b or PCV2d because it hasn’t been primed by vaccination to recognize them. This could leave the pig vulnerable to clinical disease.


Q: What vaccine strategy then is likely to protect pigs against PCV2 recombinants?

MB: The PCV2a vaccines have done a great job helping the pork industry manage PCV2 disease, but we now have a genetic gap between PCV2a-based vaccines and circulating viruses.

A vaccine with broader antigenic coverage may help fill that gap, which was the impetus for development of Fostera® Gold PCV MH. It’s the only PCV2 vaccine with two genotypes — PCV2a and PCV2b. We’ve demonstrated it protects against PCV2a, PCV2b and PCV2d as well as Mycoplasma hyopneumoniae.12 In addition, studies comparing epitopes among vaccines and field strains, including recombinants, have demonstrated it should provide broader epitopic coverage.13,14


Q: Do you have a take-home message for producers regarding PCV2 protection?

MB: It would be worthwhile to rethink the PCV2 vaccination strategy. PCV2 is an evolving virus. We’ve already got an alphabet soup of strains, ranging from PCV2a through PCV2h! To stay ahead of this virus, broader antigenic coverage needs to be considered.


All trademarks are the property of Zoetis Services LLC or a related company  or a licensor unless otherwise noted. 

1  Franzo G, et al. Phylodynamic analysis of porcine circovirus type 2 reveals global waves of emerging genotypes and the circulation of recombinant forms.  Mol Phylogenet Evol. 2016;100:269-280.
2  Neira V, et al. Genetic analysis of porcine circovirus  type 2 from pigs affected with PMWS in Chile reveals  intergenotypic recombination. Virol J. 2017;14(191).
3  Shao W, et al. Evolution of Influenza A Virus by  Mutation and Re-Assortment. Int J Mol Sci. 2017 Aug;18(8):1650.
4  He C-Q, et al. Homologous recombination evidence in human and swine influenza A viruses. Virol. 2008 Oct;380(1):12-20.
5  Franzo G, et al. Phylodynamic analysis of porcine  circovirus type 2.
6  Neira V, et al. Genetic analysis of porcine circovirus type 2.
7  Huang Y, et al. Evidence for different patterns of natural inter-genotype recombination between two PCV2 parental strains in the field. Virus Res. 2013 Jul;175(1):78-86.
8  Karuppannan A, et al. Porcine Circovirus Type 2 (PCV2) Vaccines in the Context of Current Molecular Epidemiology. Viruses. 2017 May; 9(5):99.
9  Salgado R, et al. Identification of an Emergent Porcine Circovirus-2 in Vaccinated Pigs from a Brazilian Farm  during a Postweaning Multisystemic Wasting Syndrome Outbreak. Genome Announc. 2014 Mar-Apr; 2(2):e0016314.
10  Xiao C-T, et al. Complete Genome Sequence of a Novel Porcine Circovirus Type 2b Variant Present in Cases of  Vaccine Failures in the United States. J Virol. 2012 Nov;86(22):12469.
11  Karuppannan A, et al. Porcine Circovirus Type 2 (PCV2) Vaccines.
12  Data on file, Study Report No. 16PRGBIO-01-01, Zoetis LLC.
13 Data on file, Study Report Zoetis WO1, EpiCC PCV2  Analysis, Zoetis LLC.
14  Data on file, Study Report Zoetis W02, EpiCC PCV2 Analysis, Zoetis LLC.

TOOLBOX, Issue 16
Toolbox is a series of interviews with veterinarians about their experiences managing antimicrobials, vaccines and other tools for swine health. It is produced by the editors of Pig Health Today on behalf of the US Pork Business of Zoetis.
September 2019
Share It
Recombination of porcine circovirus type 2 (PCV2) is a key consideration in control strategies – but what does the latest research say? Veterinarian Meggan Bandrick, PhD of Zoetis explains.

Click an icon to share this information with your industry contacts.

Posted on May 15, 2021

tags: ,

You must be logged in to edit your profile.

Share It
Looking at individual “pieces of the puzzle” means farm owners can evaluate the pros and cons of Mycoplasma elimination programs and come to a practical solution, says veterinarian David A. Baumert.

Click an icon to share this information with your industry contacts.
Google Translate is provided on this website as a reference tool. However, Poultry Health Today and its sponsor and affiliates do not guarantee in any way the accuracy of the translated content and are not responsible for any event resulting from the use of the translation provided by Google. By choosing a language other than English from the Google Translate menu, the user agrees to withhold all liability and/or damage that may occur to the user by depending on or using the translation by Google.