Myths and Facts about Canine Parvovirus '2c'
No evidence for substantially different properties
No evidence for substantially different properties
In recent publications and email communications a lot of attention has been given to the "new" canine parvovirus (CPV) strain, which has been designated CPV strain 2c. It is important to put this mutation into a context. This virus has a single nucleotide substitution that changes one amino acid in the capsid protein. That amino acid (of viral protein 2 (VP2) residue 426) had previously undergone a change from an asparagine to an aspartic acid to give the so-called CPV-2b strain, and in the CPV-2c variant that aspartic acid changed to a glutamic acid, a similar amino acid.
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Over the 30 years since canine parvovirus emerged in dogs it has undergone some evolution, with a small handful of changes that have been selected in the virus. Some of those mutations created small changes in the capsid surface that influence the binding to the host antibodies, and the changes of VP2 residue 426 have a small influence on the binding of some antibodies. However, dogs make a large variety of antibodies against the virus and these mutations only influence the binding of a small proportion of those, so that the immunity generated against any of the canine parvovirus strains still has a great deal of reactivity with all other strains of parvovirus.
Current Vaccines Protect Against All Strains
The research to date shows that all currently available vaccines protect against all known strains of CPV, including the newer CPV-2c strain 1,2,3. Some of the evolution of the CPV appears to give new strains small selective advantages in nature, and in some cases those can eventually replace the old variants. For example the original CPV-2 strain from 1978 is not found in nature today as it was replaced in 1980 by the CPV-2a variant. The CPV-2a is still the common virus circulating in the USA and around the world, and the CPV-2b and CPV-2c variants essentially differ from that 1980 virus at a only one or two amino acid positions 4,5.
There is no evidence that CPV-2c is a more serious threat to either shelter or owned dogs than the other CPV strains. It is not possible to distinguish CPV-2c from CPV-2b or -2a isolates based on clinical signs or parvo snap tests. CPV-2c causes similar clinical signs as the previously known strains, including mucoid or hemorrhagic diarrhea, leukopenia, and lymphopenia 4,5. Although a few reports suggest that CPV-2c may cause more severe clinical signs than -2a and -2b, others describe less-severe disease and lower mortality rates in CPV-2c infected dogs 6. There is no evidence, nor reason to believe, that the susceptibility of CPV-2c to disinfectants is different than other strains of parvovirus. All parvoviruses are environmentally persistent and resist inactivation by some common disinfectants, including quaternary ammonium compounds and alcohol. However, all strains can be reliably inactivated by correctly applied disinfectants documented to inactivate parvoviruses, including sodium hypochlorite (household bleach diluted at ½ cup per gallon) and potassium peroxymonosulfate (e.g. Trifectant ®).
CPV-2c is not known to be a particular diagnostic challenge, and is expected to cross react with commonly used ELISA tests just as other strains do. To distinguish the CPV-2c from CPV-2a/2b requires DNA sequence analysis or PCR 3; however, there seems to be little or no clinical use for these tests, as vaccine or management principles are not different.
Virus Continues to Evolve
Canine parvovirus continues to evolve, and it is possible that future variants may be altered in detection properties or vaccine susceptibility, but this has not been demonstrated to date. If unusual cases of canine parvovirus infection are suspected please contact the UC Davis Koret Shelter Medicine Program. In the meantime, the appropriate precautions when CPV is diagnosed or suspected in a shelter are the same regardless of which strain of CPV is involved.
- Schultz, R. L., L. Current Canine Parvovirus Type 2 (CPV-2) Vaccines Provide Excellent Immunity to All Genotypes of CPV-2 (eg CPV-2a, 2b, and 2c). Conference for Research Workers in Animal Diseases, Chicago. 2008
- Larson LJ, Schultz RD. Do two current canine parvovirus type 2 and 2b vaccines provide protection against the new type 2c variants. Vet Ther. 2008 Summer;9(2):94-101.
- Spibey N, Greenwood NM, Sutton D, Chalmers WS, Tarpey I. Canine parvovirus type 2 vaccine protects against virulent challenge with type 2c virus. Vet Microbiol. 2008 Apr 1;128(1-2):48-55. Epub 2007 Oct 2.
- Hong C, Decaro N, Desario C, Tanner P, Pardo MC, Sanchez S, Buonavoglia C, Saliki JT. Occurrence of canine parvovirus type 2c in the United States. J Vet Diagn Invest. 2007 Sep;19(5):535-9.
- Kapil S, Cooper E, Lamm C, Murray B, Rezabek G, Johnston L 3rd, Campbell G, Johnson B. Canine parvovirus types 2c and 2b circulating in North American dogs in 2006 and 2007. J Clin Microbiol. 2007 Dec;45(12):4044-7. Epub 2007 Oct 10.
- João Vieira M, Silva E, Oliveira J, Luísa Vieira A, Decaro N, Desario C, Muller A, Carvalheira J, Buonavoglia C, Thompson G. Canine parvovirus 2c infection in central Portugal. J Vet Diagn Invest. 2008 Jul;20(4):488-91.