Etiology of PCVD's

Porcine Circovirus 2 (PCV-2) is associated with PCVD. It is not known why some infections result in disease while others are subclinical.
The virus alone is not enough to cause disease in a herd. Environmental factors, such as drafts, overcrowding, poor air quality, co-mingling of age groups or other stressors exacerbate the severity of the disease. Co-infections with other porcine pathogens also play an important role. They are however more likely to develop lesions if inoculated simultaneously with another virus, such as porcine parvovirus (PPV) or porcine reproductive and respiratory syndrome virus (PRRSV).

About Porcine Circovirus

PCV is a small, resistant; ring shaped single-stranded DNA virus.
Two serotypes have been isolated:

• Type 1 causes no known disease.
• Type 2 can be found in the lesions and can be isolated in pure culture in piglets showing PCVAD signs

Phylogenetic groups of PCV2

Two phylogenetic groups of PCV2 have been recognized. Initial studies had indicated a lack of association of these groups with disease status or geographic area. A study on PCVD’s in Sweden, in 2005, suggested that a particular genogroup (SG3) was usually associated with PMWS occurrence, while others (SG1 and SG2) were usually not. In Canada, a restriction fragment length polymorphism (RFLP) pattern (321-like) of PCV2 was associated with severe disease outbreaks, while the RFLP pattern 422-like was linked to sporadic occurrence of PCVD. Further studies on potential pathogenicity differences among PCV2 isolates by the EU Consortium on PCVDs in Denmark and Spain also support such differences.

The EU Consortium has developed a scientific definition for PCV2 genotypes in order to standardize nomenclature.

The first two were already known and coincide with previously defined phylogenetic groups. To standardise PCV2 genotype nomenclature, the EU Consortium proposes naming those genotypes as PCV2a, PCV2b and PCV2c, following the existing proposal from Canada. Genotypes PCV2a and PCV2b have both been isolated from PMWS cases and both are pathogenic under controlled experimental conditions.

Adapted from  www.pcvd.org , June 2008 Newsletter.

Also see Press Release June 2008 - PCV2 genotype definition creates exciting opportunities. 

A piglet affected by PCVD