Kevin Vilaca from South West Ontario Veterinary Services, Is PCV3 a Common Cause of Stillbirth?

Porcine circovirus 3 (PCV3) was first detected in North America during a reproductive disease outbreak in North Carolina in 2015. Since that time, PCV3 has been detected in healthy and/or diseased swine in many countries worldwide. PCV3 has been implicated as a cause of PDNS, stillborn and mummified fetuses, encephalitis and myocarditis in perinatal, and periarteritis in growing pigs.  In a previous study these researchers had detected PCV3 in the sera of sows which had at least one stillborn piglet in the last farrowing.  In this study, the researchers wanted to investigate if the presence of PCV3 in sows’ sera could be associated to the occurrence of stillbirths on a more widespread basis. The frequency of PCV3 infections and viral DNA loads in sows’ sera was investigated through a real-time quantitative PCR in 89 serum samples of just farrowed sows with or without stillbirths.

The researchers found the following:

• PCV3 genomes were identified in most samples, with genome loads ranging between less than 10 to 200,000 copies per mL of serum. The virus was therefore relatively easy to find.
• No significant differences were observed either in the frequency of infection or PCV3 viral loads in sows with or without stillbirths.

Take Home Messages:

• No association could be established between PCV3 infection of sows at farrowing and stillbirths’ occurrence on a widespread basis. “Just because you find a bug doesn’t always mean that it is causing a disease in that pig”
• PCV3 continues to shape up as the weaker cousin of PCV2 and this virus is clearly  the cause of disease in some isolated cases but does not appear to be clinically active on a more widespread basis.

Submitted by Dr. Kevin Vilaca

Ref: Tochetto C, de Lima DA, Varela APM, Ortiz LC, Loiko MR, Scheffer CM, Paim WP, Cibulski SP, Cerva C, Herpich J, Schmidt C, Franco AC, Mayer FQ, Roehe PM.  Investigation on porcine circovirus type 3 in serum of farrowing sows with stillbirths.  Microb Pathog. 2020 Jun 10;149:104316. doi: 10.1016/j.micpath.2020.104316. [Epub ahead of print]