Kevin Vilaca from South West Ontario Veterinary Services,The Role Of PCV3: Stillborn, Mummified , Perinatal Encephalitis and Myocarditis

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Porcine circovirus 3 (PCV3) was first detected in the investigation of a reproduction disease outbreak in North Carolina in 2015. Retrospective analysis of save back laboratory samples has shown that PCV3  virus was present in the US pig population prior to 2015. PCV3 is a circovirus that is related to PCV1 and PCV2. Genetically, PCV3 is only 35 to 55 % similar to PCV2. For some time now PCV3 has been implicated as a cause of PDNS, stillborn and mummified fetuses, encephalitis and myocarditis in perinatal pigs, and periarteritis in growing pigs. In this study, the researchers had isolated 3 PCV3 viruses from weak-born piglets or elevated stillborn and mummified fetuses.

The researchers found the following:

  • Full-length genome sequences from different passages and isolates (PCV3a1 ISU27734, PCV3a2 ISU58312, PCV3c ISU44806) were determined using metagenomics sequencing.
  • Virus production in cell culture was confirmed by qPCR, IFA, and in situ hybridization.
  • In vivo ( in live animals) replication of PCV3 was also demonstrated in CD/CD pigs (n = 8) under experimental conditions.
    • the first viremia was detected at 7  days post inoculation (dpi) with all pigs viremic by 28 dpi.
    • IgM antibody response was detected between 7 to 14 dpi in 5/8 PCV3-inoculated pigs but no IgG seroconversion was detected throughout the study.
    • Pigs presented microscopic  lesions consistent with multi systemic inflammation characterized by myocarditis and systemic perivasculitis.
    • Viral replication was confirmed in all tissues by in situ hybridization.
    • None of the innoculated cd/cd pigs showed clinical signs. (as with PCV2 it may be necessary to have some other coinfections present in order to trigger more severe disease

Take Home Messages:

  • PCV3 clinical signs appear  to be more likely to appear in perinatal piglets than in older growing pigs
  • This is the first isolation of PCV3 from perinatal and reproductive cases of PCV3-associated disease and in vivo characterization of PCV3 infection in a CD/CD pig model.
  • PCV3 continues to shape up as the cousin of PCV2 that seems to show up as a cause of disease less frequently than PCV2 and when it does it focuses more on the fetus and perinatal pig.

Ref: Mora-Díaz J, Piñeyro P, Shen H, Schwartz K, Vannucci F, Li G1 Arruda B, Giménez-Lirola L.  Isolation of PCV3 from Perinatal and Reproductive Cases of PCV3-Associated Disease and In Vivo Characterization of PCV3 Replication in CD/CD Growing Pigs.   Viruses. 2020 Feb 16;12(2). pii: E219. doi: 10.3390/v12020219

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