A piglet is being vaccinated against PCV2.
herd) and further infection of foetuses during gestation. Those piglets are then born infected with PCV2. The solution is to ad- dress the immunity of the whole herd by vaccinating gilts and sows with a PCV2 vaccine approved for use in sows in addition to continuing to vaccinate piglets. Veterinarians will be able to set up a whole herd plan for effective circovirus control.
Clinical disease Recently, Prof Segalés said, “My perception is that the patho- genicity of the different PCV2 genotypes is not apparently different. We do experience systemic disease despite vaccina- tion on a very low percentage of farms, but I believe it’s much more a matter of epidemiology rather than of changing path- ogenicity of genotypes or viruses.” It is critical that any suspected PCV disease cases are investigat- ed by a vet and that laboratory diagnostics are used, including pathological examination to confirm the presence of PCV2 and the typical lesions of PCV disease under the microscope. As PCV2 can be detected by sensitive PCR tests in fully protected healthy piglets, this is not enough to confirm the disease. Finally, it is important to understand that PCV3, a newly de- tected circovirus in clinical cases (reproductive failure and wasting in piglets) should not be confused with the emer- gence of different strains of PCV2. PCV3 is considered a sepa- rate species which shares only 50% genetic identity with PCV2, and no cross-protection from existing PCV2 vaccines should be expected.
References available on request. ▶ PIG PROGRESS | Volume 37, No. 4, 2021 9
Table 1 – Summary of published studies demonstrating cross protection of a PCV2-a based vaccine against the most prevalent genotypes of PCV2
Paper Licensing Data* Takahagi et al, 2009
Desrosiers, 2009 Cline et al, 2008
Haiwick et al, 2014 Rodier et al, 2014
Type of study
Lab challenge Field trial
Field trial Field trial
Lab challenge Lab challenge
Opriessnig et al, 2014 Lab challenge Jeong et al, 2015 Rose et al, 2016 Payne et al, 2016
Field trial
Lab challenge Field trial
Huang et al, 2016 Fano et al, 2017 Philips et al, 2017 Lebret et al, 2017 Park et al, 2019
Friedrich et al, 2019 Lab challenge Farm scale challenge Lab challenge Lab challenge Farm scale challenge Country
US, Europe Japan
Canada US US US US
Korea France US
China US
Farm scale PRDC challenge US Case report
France Korea
US
Romanov et al, 2020 Case report (reproductive) Ukraine Fano et al, 2021
US
Field strain(s) challenging pigs Heterologous PCV2-a
Heterologous PCV2-a, PCV2-b PCV2-b PCV2-b PCV2-b PCV2-b PCV2-d
PCV2-b, PCV2-d PCV2-b
Heterologous PCV2-a, PCV2-b, PCV2-d PCV2-b PCV2-d PCV2-d PCV2-d
Heterologous PCV2-a, PCV2-b, PCV2-d PCV2-d PCV2-d PCV2-d
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