Farmscape for November 18, 2025

A swine vet with Merck Animal Health says the various strains of Porcine circovirus are similar but their animal health implications differ.
PCV1, the first strain of Porcine circovirus, was identified in the 1970s followed a couple of decades later by PCV2 then in 2015 by PCV3 and in 2019 by PCV4.
"PCV3: How It Started versus How It's Going," was discussed earlier this month as part of Saskatchewan Pork industry Symposium 2025.
Dr. Carol Malgarin, a swine veterinarian-technical support with Merck Animal Health, says the strains are similar enough in their genomic sequencing to belong to the same family but they do have differences.

Quote-Dr. Carol Malgarin-Merck Animal Health:
For example, PCV1 is similar to PCV2 but it doesn't have the pathogenic properties as PCV2.
PCV3 is the most different one so far.
It's not super close to PCV2 but it does hold the ability to also cause disease and PCV3 and PCV4 are closer together.
They are able to cause inflammation especially close to the blood vessels of the animal.
It's not completely understood what determines if they are going to be a reproductive disease, a systemic disease or for example the porcine dermatitis and nephropathy syndrome that we can see in PCV2.
That is not very clear but they are able to cause disease, especially when they have coinfections with other pathogens.
They have been found in many different species that won't necessarily get sick as pigs do but they can be carriers.
For PCV3, for example we have found them in wild boar, in wildlife like in deer, we have found them in cattle, dogs and even ticks and mosquitos,
We do believe these animals might not get sick as pigs do but they can be carriers of PCV3 within the domestic pig population if they are in close contact.

Dr. Malgarin suggests we need to learn more about Porcine circovirus, especially PCV3 and why it causes the kind of lesions it causes and how it interacts with coinfections and we need to learn more about the pathogenicity of PCV4.
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Bruce Cochrane.

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