Porcine Circovirus: The Ever-Present, Ever-Changing Virus
Porcine Circovirus Type Two (PCV2) can be found in all pig populations globally and is seemingly impossible to eradicate from a pig herd. PCV2 vaccines are good at controlling clinical disease; most notable of PCV2 clinical disease is PMWS and PDNS, but the virus can also play a role in respiratory disease, reproductive disease, and diarrhoea. So why can we mostly control the clinical disease, but the virus is still rife in our herds? This is mainly due to the virus’ structure and the way it reproduces:
Figure 1 Impact and Cost of Subclinical PCV2 Infection
PCV2 vaccines have historically been based on the first genotype of PCV2 that was identified, PCV2a; but now the dominant strains have shifted globally from PCV2a to PCV2b and then PCV2d. Interestingly PCV2d is so similar to PCV2b (Up to 97.7%) it was originally called mutant-subtype PCV2b. A recent survey by Zoetis (Figure 2) showed presence of all three genotypes still circulating in the UK pig population.
Figure 2: UK PCV2 Genotypes Zoetis Survey 2021
Traditional PCV2a vaccines have demonstrated an ability to cross protect against clinical disease caused by other genotypes (PCV2b, PCV2d etc.) but a recent scientific paper by Bandrick et al., (2022) has proven that a vaccine which is matched to the farm genotype will give better biological protection e.g. a PCV2a vaccine will protect better against PCV2a infection than it will against PCV2b infection. Furthermore, the paper demonstrated that a vaccine which contains multiple PCV2 genotypes gives better biological protection against PCV2 pathologies than a vaccine which only contains a single genotype. The CircoMax range, from Zoetis, are the only PCV2 vaccines that contain multiple genotypes (PCV2a and PCV2b antigen) providing protection against PCV2a, PCV2b and PCV2d, representing the three dominant PCV2 strains in the UK. Currently in the market is CircoMax Myco which is a combined one dose product providing protection against PCV2a, PCV2b, PCV2d and Mycoplasma hyopneumoniae (M.hyo) in a single shot. Coming soon will be CircoMax, the only PCV2 vaccine, not combined with M.hyo, that is licensed to protect against PCV2a, PCV2b and PCV2d.
Would you like to know what PCV2 genotype you have circulating on your farm? We offer a complimentary genotyping service which can be organised through your consulting/prescribing vet. Please email us at [email protected] if you would like to arrange this or discuss PCV2 genotypes further.
Dr Laura Hancox, Zoetis National Veterinary Manager
Click here to learn more...
References: Bandrick M, Balasch M, Heinz A, Taylor L, King V, Toepfer J, Foss D. A bivalent porcine circovirus type 2 (PCV2), PCV2a-PCV2b, vaccine offers biologically superior protection compared to monovalent PCV2 vaccines. Vet Res. 2022 Feb 18;53(1):12.
CircoMax® Myco contains inactivated recombinant chimeric porcine circovirus type 1 containing the porcine circovirus type 2a open reading frame 2 (ORF2) protein, inactivated recombinant chimeric porcine circovirus type 1 containing the porcine circovirus type 2b (ORF2) protein and inactivated Mycoplasma hyopneumoniae, strain P-5722-3. POM-V. CircoMax® contains two inactivated recombinant chimeric porcine circovirus type 1s, containing open reading frame 2 (ORF2) of porcine circovirus type 2a and 2b respectively. POM-V
Use medicines responsibly (www.noah.co.uk/responsible). Further information can be obtained from the product SPC or from Zoetis UK Limited, 1st Floor, Birchwood Building, Springfield Drive, Leatherhead, Surrey, KT22 7LP. www.zoetis.co.uk Customer Support: 0345 300 8034. Date of preparation: September 2023. MM-28071
Porcine Circovirus Type Two (PCV2) can be found in all pig populations globally and is seemingly impossible to eradicate from a pig herd. PCV2 vaccines are good at controlling clinical disease; most notable of PCV2 clinical disease is PMWS and PDNS, but the virus can also play a role in respiratory disease, reproductive disease, and diarrhoea. So why can we mostly control the clinical disease, but the virus is still rife in our herds? This is mainly due to the virus’ structure and the way it reproduces:
- It is very resilient in the environment. It can tolerate extremes of temperatures and pH, so cleaning and disinfection (C&D) will lower the amount of PCV2, but not eliminate it entirely.
- It replicates best in disease challenged pigs. PCV2 particularly likes to replicate within cells of the pigs which are themselves fast replicating, such as those in the immune system which replicate at a particularly high level in response to infection. So, the more disease challenged the pig is, the more PCV2 will replicate, and the more susceptible/challenged the pig will further become.
- Subclinical disease is the most common form of infection. Subclinical PCV2 infected pigs are more susceptible to other endemic diseases, have lower growth rates, and will shed virus to the rest of the herd. Subclinical disease has significant economic impacts (Figure 1).
- The virus is rapidly evolving. The virus is rapidly mutating, and in addition around 1 in 3 PCV2 strains found on farms are recombinant, meaning different PCV2 viruses have merged together to make a new strain. It has been shown that vaccination can influence the genomics of PCV2 populations on a pig farm, meaning current vaccines could be driving the evolution of the virus.
Figure 1 Impact and Cost of Subclinical PCV2 Infection
PCV2 vaccines have historically been based on the first genotype of PCV2 that was identified, PCV2a; but now the dominant strains have shifted globally from PCV2a to PCV2b and then PCV2d. Interestingly PCV2d is so similar to PCV2b (Up to 97.7%) it was originally called mutant-subtype PCV2b. A recent survey by Zoetis (Figure 2) showed presence of all three genotypes still circulating in the UK pig population.
Figure 2: UK PCV2 Genotypes Zoetis Survey 2021
Traditional PCV2a vaccines have demonstrated an ability to cross protect against clinical disease caused by other genotypes (PCV2b, PCV2d etc.) but a recent scientific paper by Bandrick et al., (2022) has proven that a vaccine which is matched to the farm genotype will give better biological protection e.g. a PCV2a vaccine will protect better against PCV2a infection than it will against PCV2b infection. Furthermore, the paper demonstrated that a vaccine which contains multiple PCV2 genotypes gives better biological protection against PCV2 pathologies than a vaccine which only contains a single genotype. The CircoMax range, from Zoetis, are the only PCV2 vaccines that contain multiple genotypes (PCV2a and PCV2b antigen) providing protection against PCV2a, PCV2b and PCV2d, representing the three dominant PCV2 strains in the UK. Currently in the market is CircoMax Myco which is a combined one dose product providing protection against PCV2a, PCV2b, PCV2d and Mycoplasma hyopneumoniae (M.hyo) in a single shot. Coming soon will be CircoMax, the only PCV2 vaccine, not combined with M.hyo, that is licensed to protect against PCV2a, PCV2b and PCV2d.
Would you like to know what PCV2 genotype you have circulating on your farm? We offer a complimentary genotyping service which can be organised through your consulting/prescribing vet. Please email us at [email protected] if you would like to arrange this or discuss PCV2 genotypes further.
Dr Laura Hancox, Zoetis National Veterinary Manager
Click here to learn more...
References: Bandrick M, Balasch M, Heinz A, Taylor L, King V, Toepfer J, Foss D. A bivalent porcine circovirus type 2 (PCV2), PCV2a-PCV2b, vaccine offers biologically superior protection compared to monovalent PCV2 vaccines. Vet Res. 2022 Feb 18;53(1):12.
CircoMax® Myco contains inactivated recombinant chimeric porcine circovirus type 1 containing the porcine circovirus type 2a open reading frame 2 (ORF2) protein, inactivated recombinant chimeric porcine circovirus type 1 containing the porcine circovirus type 2b (ORF2) protein and inactivated Mycoplasma hyopneumoniae, strain P-5722-3. POM-V. CircoMax® contains two inactivated recombinant chimeric porcine circovirus type 1s, containing open reading frame 2 (ORF2) of porcine circovirus type 2a and 2b respectively. POM-V
Use medicines responsibly (www.noah.co.uk/responsible). Further information can be obtained from the product SPC or from Zoetis UK Limited, 1st Floor, Birchwood Building, Springfield Drive, Leatherhead, Surrey, KT22 7LP. www.zoetis.co.uk Customer Support: 0345 300 8034. Date of preparation: September 2023. MM-28071
