Canine Parvovirus Type 2c in the United States

For many years vaccinated dogs have suffered and died from CanineParvovirus (CPV) infections. Since vaccination failed to protect these dogs, peoplespeculated that a new form of CPV was in our midst. Their speculation hasbeen substantiated by the recent press release from Oklahoma State Universitywhich stated that a new form of CPV (CPV-2c) has been identified in dogsacross the United States by the Oklahoma Animal Disease Diagnostic laboratory 1.The press release stated that the 2c strain affects puppies and adults, canattack the heart and intestines, and that the mortality can be quite high.The most alarming aspect of the press release is its implication thatcurrently available vaccines are not protective against this lethal CPV-2c strain.This is obviously troubling news fore all dog owners. So we must ask, isthe press release completely true, or does it contain exaggerations intendedto whip up unnecessary hysteria?

The press release is based on the results of a study published by Dr. Kapiland his colleagues in the Journal of Clinical Microbiolgy2. In this study,tissue and fecal samples were collected between February 2006 and August2007 from 54 dogs with confirmed CPV infections. Canine parvovirus type 2c wasidentified in 48% of the dogs while CPV-2b was identified in 46% of thedogs. The researchers also that 66% of the dogs infected with various strains ofCPV had previously received a vaccination.

Since implications of the press release are so frightening, we must digdeeper into the CPV-2c story to fully understand what it means for dog ownersand breeders. The emergence of this new strain of CPV is not surprisingconsidering the history of CPV and the high rate of viral evolution associatedwith its initial emergence in the 1970s. Since the emergence of CPV type 2(CPV-2) in the 1970s the virus has mutated. The v irus mutated into 2 strainsknown as CPV-2a and CPV-2b. In 2000 scientists in Italy were the first toreport the emergence of CPV-2c in dogs. Since that report, CPV-2c has beenreported in Western Europe, Asia, and South America.

Now that a new strain of CPV is present throughout the world, the questionarises: What is meant by the term new strain? We need to realize that theterm new strain actually means genetic variant. In order for a strain ofparvovirus to be labeled a new strain, at least 1 of its approximately 5000nucleotides must be different from a previously identified strain. This is thecase of the CPV-2c identified in the United States. Genetically speaking,CPV-2c differs from CPV-2b by only a few nucleotides. In other words, from agenetic standpoint, the new strain(CPV_2c) is over 99% identical to the oldstrain (CPV-2b).

So there is very little genetic difference between CPV-2a, CPV-2b, andCPV-2c. Does this sligh t genetic variation make CPV-2c biologically differentfrom CPV-2a or CPV-2b? The most prolific researcher of CPV-2c in Italyconcluded in a research report that CPV variants (2a, 2b, and 2c) have similarbiological behaviors3. In that research report, tissue distribution of CPV wassimilar across all 3 genetic variants of CPV. Canine parvovirus type 2a,2b, and 2c were all found in the intestines and in the heart. So the fact thatCPV infects the heart and the intestines is not new information and is notspecific to only CPV-2c. In another paper that investigated the occurrenceof CPV-2c in the United States, researchers stated that dogs infected withCPV-2c exhibited clinical signs and outcomes that were similar to dogs infectedwith CPV-2a and CPV-2b4. So death of dogs due to CPV infection (be it 2-a,2-b, or 2-c) is not new information and it is erroneous to suggest thatCPV-2c is more lethal then older CPV strains.

Since CPV-2c has been discovered in the United Stat es, what are dog ownersand breeders to do? According to the press release, new vaccines should beformulated since previously vaccinated dogs have contracted CPV-2c. Shouldyou switch vaccines? Should you demand vaccine manufacturers make a newvaccine that protects against CPV-2c? The answer to the 2 previous questionswould be yes if we did not have some suitable vaccines currently available foruse. With the information now available in the scientific literature, Ibelieve that there is no reason to suggest that the currently available effectivevaccines will not protect against CPV-2c. Let me explain why I believe thisto be true.

First, a recent research report indicated that one of the original modifiedlive CPV vaccines (based on an old strain of CPV) was protective againstCPV-2c. This study reported that after CPV-2c challenge, vaccinated pups did notbecome ill while unvaccinated pups showed clinical signs of canineparvovirus5. In other words, on of the fir st vaccines, which was formulated yearsbefore CPV-2c was identified, was able to induce protection against this newgenetic variant known as CPV-2c.

Second, certain effective CPV vaccines protect puppies against both CPV-2aand CPV-2b. Since there is very little genetic variant and no knownbiological differences between CPV-2a, CPV-2b, and CPV-2c, why wouldn't theseeffective CPV vaccines protect against CPV-2c? To my Knowledge, no one has data todefinitively answer the question posed above.

Third, NEOPAR© has been tested in a kennel in Oklahoma where this newgenetic variant was diagnosed by the Oklahoma Animal Disease DiagnosticLaboratory. NEOPAR©, when used properly, stopped the CPV-2c in its tracks just likeit stops a CPV-2a and CPV-2b outbreak.

One disturbing aspect of the press release and Dr. Kapil's paper was thatvaccines do not protect against CPV-2c. In Dr. Kapil's study, 66% of the dogswere previously vaccinated. It is important to rea lize that not allvaccines stimulate protection after just one, or multiple, doses. Immunity is oftennot stimulated by vaccination if the animal is stressed, has a suppressedimmune system, or if the vaccine used is sub-potent (few vaccine particlesper dose). Unfortunately, the complete vaccination history for each dog in DrKapil's study was not provided. So, it is possible these dogs could havebeen vaccinated after they were exposed to CPV or they may have been vaccinatedwith a sub-potent vaccine prior to CPV exposure. Many sub-potent vaccinesare on the market today and were not formulated to work in the face of thehigh level of maternal antibody when pups are first vaccinated at 5 to 7 weeksof age. This high level of maternal antibody can render a sub-potentvaccine ineffective. Another important point of Dr. Kapil's study to consider isthat vaccinated dogs were infected with CPV-2b and CPV-2c. Of the 36vaccinated dogs in which CPV was identified, type 2b was presen t in 15 dogs and type2c was present in 19 dogs. So, not only did vaccination fail to protectthese dogs against CPV-2c, vaccination also failed to protect them against theolder genetic variations of CPV. Clearly, vaccines do not immunize 100% ofvaccinated dogs and this is also not new information.

At the present time, we know very little about CPV-2c. However, informationpresent in the scientific literature suggests that CPV-2c is very similarto CPV-2a and CPV-2b; and, that vaccines developed prior to the discovery ofCPV-2c protect dogs from CPV-2c challenge. Even though the full CPV-2c storyhas not yet been established, this has not stopped people from makingpredictions of doom and gloom. Lets not get bogged down by the press releaseintended to whip up hysteria in hopes of creating an economic opportunity for aresearch institution. Let's wait until we have more relevant facts aboutthis genetic variant before we recommend changing the existing vaccinationprotoc ols that have been so successful for so many years. In essence, all thatDr. Kapil's report stated is that CPV-2c (along with other old geneticvariants of CPV) has been identified in previously vaccinated dogs in the UnitedStates. So the implications of the press release of widespread death due toan extremely pathogenic new strain of CPV are a bit far reaching. Let me beclear. Dr. Kapil's study is scientifically sound and the results are clearand straightforward, but the press release is an exaggeration of what isknown and speculates on what we do not know.




References

1 _http://www.cvhs.okstate.edu/index.php?o_(http://www.cvhs.okstate.edu/index.php?o) .. itemid=291_<http://www.cvhs.okstate.edu/index.ph...k=view&id= 437&itemid=291>_ (http://www.cvhs.okstate.edu/index.php?option=com_content&task=view&id=437&item id=291)

2Kupil, S., Cooper, E., Lamm, C., Murry, B., Rezabek, G., Johnson III, L.,Campbell, G., Johnson, B. 2007 Canine Parvovirus types 2c and 2bcirculating in North American dogs in 2006 and 2007. J. Clin. Microbial.,45(12):4044-4047

3Decaro, N., Martella, V., Elia, G., Desario, C., Campolo, M., Lorusso, F.,Colaianni, M. L., Lorusso, A., Buon-avoglia, C. 2007 Tissue distribution of the antigenic variants of canineparvovirus type 2 in dogs. Vet Microbial. 2007 Mar 31 1;121(1-2):39-44

4Hong, C., Decaro, N., Desario, C., Tanner, P., Pardo, M.C., Sanchez, S.,Buonavoglia, C., Saliki, J.T. 2007 Occurrence of canine parvovirus type 2c inthe United States. J. Vet. Diagn. Invest. 19:535-539

5Spibey, N., Greenwood, N.M., Sutton, D., Chalmers, W.SK., Tarpey, I. 2008Canine parvovirus type 2 vaccine protects against virulent challenge withtype2c virus. Vet. Microbiol. Apr 1;128(1-2):48-55. Epub. 2007 Oct 2.




Canine Parvovirus Type 2c in the United StatesDr. Ben Hatler, NEOTECH, LLC