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Parvovirus in Dogs
What is canine parvovirus? It is first necessary to distinguish between canine parvovirus 1, or minute virus (CMV), and canine parovirus 2 (CPV2). Minute virus is genetically similar to bovine parvovirus and belongs to the Bocavirus genus. It can be passed on to puppies if the dam is infected during pregnancy. CMV can produce gastroenteritis symptoms and can be serious or fatal in young animals. Canine minute virus is genetically unrelated to CPV2.
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What Is Canine Parvovirus 2?
Canine parvovirus 2, or CPV2, is a small (less than twenty-six nanometres) single-stranded uncoated DNA virus which infects dogs and wild canids, although it can infect both domestic and wild cats as well. It is now more properly known as merely CPV rather than CPV2.  CPV2 is part of the Parvoviridae genus. There are a number of sub-types of this canine parvovirus: the original CPV2 has been superceded by CPV2a, CPV2b and CPV2c.
The virus has a close genetic similarity to feline leukopenia (FLP). The two viruses differ at only two nucleotides, but these differences allow for infection activity in canines.  Prevalence of the disease is now reduced due to improved prevention and vaccination programs.
Some types of dog are thought to be more susceptible to the canine parvovirus: one factor increasing susceptibility is breed. Breeds such as e.g. sled dogs and Springer Spaniels are quoted by Barr, C.S and Bowman, D.D. as more susceptible to CPV2.
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Symptoms of Canine Parvovirus.
Parvovirus in dogs may manifest with cardiac or intestinal symptoms. The virus needs rapidly dividing cells to replicate. This means the organs in the body with rapidly dividing cells are targets: lymph, gut, bone marrow, and in the puppy, the heart. In symptomatic intestinal CPV2 infections, infection first takes hold in the tonsils and lymphatic system before attacking the gastrointestinal system: symptoms include nausea and bloody diarrhoea. If left untreated it can lead to white blood cell destruction, dehydration and sepsis and may prove fatal.
The canine parvovirus can be transferred to puppies during pregnancy although the dam may have no evidence of disease. Results may include fatal cardiac inflammation depending on the timing of the dam's infection. Puppies with gastroenteritis as a result of CPV2 may be treated with intravenous fluids and antibiotics.
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Treatments For Parvovirus in Dogs
There is no specific anti-viral drug to treat CPV2. Treatment for symptoms of parvovirus in dogs includes i.v. fluids and electrolytes, antibiotics (as CPV2 can result in septicaemia: lesions in the gut can lead to escape of bacterial toxins into the body), anti-emetics and pain medication: these allow the body to mount its own counter-attack.
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Prevention and Vaccination Against CPV2
The virus is spread by dog-to-dog contact via oral contact with faeces or infected soil, items or humans. CPV2 is a very hardy virus and may not be killed for long periods in soil or on infected items such as blankets. Bleach of the correct strength however will kill it, although heat, cold and most other chemicals are ineffective. The parvovirus has no lipid membrane and therefore substances which attack such membranes e.g. detergents are ineffective against it.
Prevention of infection and restriction of transfer is necessary to protect against CPV2. Current vaccines are effective against CPV2a and CPV2b and provide broad protection, although they are not specifically designed for the newest variant CPV2c. Appropriate vaccination of puppies, adult dogs and dams, immunity testing and quarantine of infected animals combined with excellent hygiene is the best route to protecting your dog.
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Researchers are now looking at the potential of CPV as a drug delivery mechanism. The virus capsid binds well to the transferrin receptor found on canid cells, and also on rapidly dividing human tumour cells. This renders it a good candidate for drug delivery.
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1. Mahy, B.W.J. “The Dictionary of Virology.", p.77. Burlington: Academic Press, 2009.
2. Barr, S.C. & Bowman, D.D. “The 5-minute Veterinary Consult Clinical Companion: Canine and Feline Infectious Diseases and Parasitology.", pp. 99-105. Ames: Blackwell Publishing, 2006.
3. Manchester, M. & Steinmetz, N. “Viruses and Nanotechnology.", pp.124-132. Berlin: Springer-Verlag, 2009.
4. Tilley, L.P. “Manual of Canine and Feline Cardiology.", pp. 270-271. St. Louis: Saunders, 2008.
5. Spibey, N., Greenwood, N.M., Sutton, D., Chalmer, W.S.K., Tarpey, I. "Canine parvovirus type 2 vaccine protects against virulent challenge with type 2c virus." Veterinary Microbiology. 128:1-2, 01/04/08, pp.48-55