Canine parvovirus: An update on variants - DVM
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Canine parvovirus: An update on variants
A review of what's happening with canine parvovirus in the United States.


DVM360 MAGAZINE


Vaccine failure

Under field conditions, vaccine failures happen. The most common reason is the incomplete take of the MLV vaccine due to interference from maternal antibodies. This problem is exacerbated due to less efficient neutralization of the variant CPV-2 isolates that have emerged recently.

Other factors, such as biological variation among CPV-2 isolates, may be responsible for the recent CPV-2c problems. In the last three years, the frequency of GCA at position 440 has increased in the CPV-2c isolates. The CPV-2c and CPV-2b isolates recovered from puppies older than 5 months have a higher frequency of GCA at position 440 compared to ACA among CPV-2c and CPV-2b isolates recovered from puppies younger than 5 months.

Disinfection

Canine parvovirus is resistant to most common disinfectants. Household bleach (1:30 dilution in water) and potassium peroxide (Trifectant or Virkon) are suitable for all CPV-2 outbreaks. Ten minutes of exposure to these chemicals will destroy CPV-2 virus. All canine parvovirus isolates have similar properties. Items that cannot be treated with either of these chemicals can be disinfected with steam.

Geographic distribution

To date, CPV-2c has been detected in samples from a total of 15 states. Unrestricted movement of infected dogs has been responsible for transatlantic transmission of CPV-2c from Italy. Highest numbers of CPV-2c cases have been detected in Oklahoma. The geographic and regional monitoring is important so that proper genotypes can be selected for vaccine production in different countries of the world. Moreover, it will be important to understand how to introduce the vaccines with different genotypes in different U.S. states. It will be prudent to continue using the current MLV CPV-2 vaccines for most of the states and to introduce CPV-2c as soon as it becomes available.

Effects on wildlife

Canine parvovirus is a major threat to conservation of wolves. About half of the wolf puppies in Minnesota have succumbed to canine parvovirus. Carnivore parvovirus isolates have caused disease in Lynx, bobcats and raccoons. There are few studies in which the wildlife parvovirus isolates have been characterized. Most have used serology to detect the exposure.

Conclusions

Canine parvovirus emerged about 30 years ago. The virus has spread rapidly across continents, undergoing rapid evolution in adapting to the new host. Due to movement of dogs, CPV-2c has spread worldwide and CPV-2c has become the major genetic variant in Europe.

In the United States, CPV-2c is accounting for more cases of canine parvovirus infection. CPV-2c cannot be clinically distinguished from other CPV-2 genotypes. CPV-2c is mostly a disease of young puppies. There is a debate over whether the canine parvovirus-2 vaccines need to be updated.

Several groups, including vaccine companies, have shown that current vaccines provide protection against the Italian CPV-2c isolate under experimental conditions in sero-negative dogs. Based on large numbers of independent reports from dog breeders in the south-central states, current vaccines need to be carefully evaluated for their efficacy against current circulating CPV-2 isolates.

At least three independent published reports suggest that CPV-2 isolates can differ in their biological properties and CPV-2 isolates (about 30 percent) can have significant antigenic differences (about 10-fold). This level of antigenic distance is significant and will make a difference in puppies that are maternal antibody-positive at 6 weeks of age.

It has been recommended to give a booster shot to puppies at 4 months of age to cover the emerging CPV-2c isolates. This additional booster vaccine will help increase the number of puppies (population immunity) that have actively seroconverted before they are put in the CPV-2 contaminated environment.

by Johnny D. Hoskins DVM, PhD, Dipl. ACVIM

Dr. Hoskins is owner of Docu-Tech Services. He is a diplomate of the American College of Veterinary Internal Medicine with specialities in small animal pediatrics. He can be reached at (225) 955-3252, fax: (214) 242-2200 or e-mail:


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Source: DVM360 MAGAZINE,
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