It’s NOT Circovirus

A look at the PCV2 assembly

A disease characterized by lethargy, vomiting, diarrhea, necrotizing vasculitis killed several dogs in Ohio. Early tests found the presence of the newly discovered Dog circovirus (CaCV) in diseased dogs and media reports quickly implicated circovirus.

They were wrong.

A report from the American Veterinary Medical Association reports that circovirus wasn’t responsible for the outbreak and only 2 of the 15 dogs tested tested positive for circovirus. The hunt continues.

There is some question as what to call this virus. Kapoor et al isolated a circovirus from healthy dogs and named it Canine circovirus [CaCV]. Li et al (Li 2013) isolated the virus from diseased dogs and fully sequence two genomes naming it Dog circovirus [DogCV]. The viruses are very similar and share a 96-97% nucleotide identity. If I understand ICTV naming criteria, they should bear the same name.

I suspect that when things are settled,  they will get a numerical designation much like the similar porcine circovirus 1 and 2 (PCV1 and PCV2).-

Some of the articles I’ve read had comments bemoaning the lack of progress in identifying and determining what was killing the dogs. If only lab work was as fast, as easy and as definitive as it is on TV.

In order to confirm a virus is causing a disease, we still have to do it the old-fashioned way; isolate the virus from a diseased animal, introduce it to a healthy subject and see if the isolated virus causes the same disease in a healthy specimen. Even after all these years Koch’s postulates hold (mostly) true – with some modifications for viruses and modern molecular methods (Rivers 1937, Fredricks 1996). At the very least we need some animal cell lines that will support DogCV.  To make matters more difficult, circoviruses are often found along with other viruses, may potentiate secondary infections and can show up in healthy and diseased animals (Li 2013).

I’m disappointed. The same organizations and bloggers that were quick to jump on circovirus bandwagon have all but ignored the JAVMA report. It pays to alarm people, not so much to inform them.

Another look at PCV2 assembly

REFERENCES

Rivers TM (1937) Viruses and Koch’s postulates. J Bacteriol. 1937 January; 33(1): 1–12.

Fredericks DN, & Relman DA (1996). Sequence-based identification of microbial pathogens: a reconsideration of Koch’s postulates. Clinical microbiology reviews, 9 (1), 18-33 PMID: 8665474

Li L, McGraw S, Zhu K, Leutenegger CM, Marks SL, Kubiski S, Gaffney P, Dela Cruz FN Jr, Wang C, Delwart E, & Pesavento PA (2013). Circovirus in tissues of dogs with vasculitis and hemorrhage. Emerging infectious diseases, 19 (4), 534-41 PMID: 23628223

Kapoor A., Dubovi E.J., Henriquez-Rivera J.A. & Lipkin W.I. (2012). Complete Genome Sequence of the First Canine Circovirus, Journal of Virology, 86 (12) 7018-7018. DOI: 10.1128/JVI.00791-12