Porcine Circovirus

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1. Classification

a. Higher order taxa

Viruses do not have a domain, phylum or class. Thus, the taxa begins at order. Porcine circovirus is classified as follows:

Viruses; ssDNA viruses; Circoviridae; Circovirus; unclassified Circovirus

2. Description and significance

Circoviruses are small ssDNA viruses which can inhabit and infect several hosts. Porcine circoviruses commonly infect swine (2). There are two main serotypes: Porcine circovirus 1 (PCV1) and Porcine circovirus 2 (PCV2). There is current research into another emerging serotype, Porcine circovirus 3 (PCV3), which is very similar to PCV2, but is not yet an epidemic in swine (13). PCV1 is not known to demonstrate any sign of disease, whereas PCV2 can cause an illness called Porcine circovirus Associated Disease (PCVAD), which causes Post Weaning Multisystemic Wasting Syndrome (PMWS) (3, 4). Porcine circovirus has one of the highest evolution rates of DNA viruses and also has the capability to co-infecting hosts along with other pathogens. This can lead to more severe outbreaks and complex syndromes involving reproductive failure, enteritis and pneumonia (5).

The Porcine circovirus has the smallest genome of any autonomously replicating virus (5). The small size of the genome presents many challenges when attempting to study the pathology of the virus in livestock. The circovirus can affect a variety of hosts (mostly livestock); moreover, Porcine circovirus infection can have detrimental effects on agricultural business as it can kill off an entire swine herd, and hence cut into profits (6). Infection results in a high fatality rate in swine populations, even though a vaccine has been created to protect against PMWS. The circovirus’ small genome allows for fast evolutionary adaption, permitting the virus to quickly gain resistance to these vaccines (5, 7). This is due to the fact that one or two mutations could have a huge effect on the virus, such as making a benign circovirus pathogenic (3).

3. Genome structure

The Porcine circovirus has two major serotypes, type 1 and type 2 (PCV1 and PCV2) and one emerging serotype, type 3 (PCV3) (13). PCV1 is known to be benign, while PCV2 is pathogenic (3, 4). Porcine circovirus 2 (PCV2) is a small, non-enveloped virus with a circular single-stranded DNA genome which is 1.76kb (6, 8). Since the genome of circovirus is small it also allows for more recombination events with other similar viruses. For example, it has been shown historically through phylogenetic analysis that a nanovirus and a circovirus at some point recombined, as a circovirus has some RNA segments in its genome even though it is a ssDNA virus (2). The DNA sequence similarity between the two serotypes, PCV1 and PCV2, is about 76% (9).

4. Cell structure

Interesting features of cell structure. Can be combined with “metabolic processes”

5. Metabolic processes

Describe important sources of energy, electrons, and carbon (i.e. trophy) for the organism/organisms you are focusing on, as well as important molecules it/they synthesize(s).

6. Ecology

Habitat; symbiosis; contributions to the environment.

7. Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

7. Key microorganisms

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8. Current Research

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9. References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.