Porcine Circovirus (PCV) is a single stranded DNA virus (class II), that is non-enveloped with an un-segmented circular genome. The viral capsid is icosahedral and approximately 17 nm in diameter. PCV is a member of the virus family Circoviridae.
PCV are the smallest viruses replicating autonomously in eukaryotic cells. They replicate in the nucleus of infected cells, utilising the host polymerase for genome amplification.
There are 2 strains: Type 1 PCV and Type 2 PCV.
Type 1 PCV (first identified in 1974) readily infects but is not known to cause disease in swine; it is the type 2 that has caused problems in recent years with the increasing occurrence of postweaning multisystemic wasting syndrome (PMWS) which over time results in significant depletion of lymphocytes; post mortem of diseased animals reveals enlarged lymph nodes and abnormal lung tissue.
It is still unclear whether type 2 PCV (first isolated in 1997) actually causes PMWS, as infection with the virus alone causes no clinical signs, it appears to work synergistically with parvovirus, perhaps with parvovirus activating a latent form of circovirus or weakening the immune system enough for PCV to take hold. PCV1 and PCV2 show a high degree of sequence homology and a similar genomic organisation; nevertheless, the basis of the distinct pathogenicity has not yet been unravelled.
An effective vaccination is now available. Fort Dodge Animal Health (Wyeth) launched the first USDA approved vaccine in 2006, containing an inactivated virus (ATCvet code: QI09 AA07 ).
See also
- Animal viruses
References
- ^ a b Mankertz P (2008). "Molecular Biology of Porcine Circoviruses". Animal Viruses: Molecular Biology . Caister Academic Press. ISBN 978-1-904455-22-6 . http://www.horizonpress.com/avir .
External links
- The Control of Porcine Circovirus Diseases (PCVDs): Towards Improved Food Quality and Safety
- Animal Disease Diagnostic Laboratory
- Porcine Circovirus Type 2
- Swine health fact sheet
- The Ecomonics of PMWS - Porc Quebec Magazine Article
- Animal viruses
- Stopcircovirus.com
- Viralzone :
Porcine circovirus - Wikipedia, the free encyclopedia
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