Canine Parvovirus (CPV/parvo)

Introduction

Parvovirus is highly contagious, incredibly durable in the environment, and capable of producing severe or life-threatening disease in dogs. It is critical to prevent transmission of the disease and rapidly identify infected animals in order to provide medical care as deemed appropriate and protection to other dogs in the shelter. Inevitably, Parvovirus will be introduced into shelters from the surrounding community from time to time. If this occurs where preventive medicine is not practiced, in a crowded, busy shelter where staff is already stretched to the maximum, the response to the epidemic is a crisis mode, which is inefficient, very expensive, and much less effective at protecting animals from this deadly disease.

Parvovirus facts

1. Parvovirus is very durable in the environment and can persist  for months or years.
2. Bleach or potassium peroxymonosulfate (Trifectant or Virkon-S) have been proven to kill parvovirus if used correctly. For more information on parvocidal disinfectants, click here.
3. There is no way to completely disinfect contaminated dirt and grass, although sunlight and drying has some effect. Mechanical decontamination through irrigation may also be helpful, but the area must be allowed to dry thoroughly between applications. Potassium peroxymonosulfate has relatively good activity in the face of organic matter, and can be sprayed on contaminated areas using a pesticide sprayer or other applicator. To be on the safe side, contaminated areas should be off limits to puppies for 1-6 months (choose the longer end of the waiting interval for moist, dark areas, if area can not be heavily irrigated or if it can not be sprayed with potassium peroxymonosulfate).
4. Parvovirus can be spread on hands, feet, clothing, tools, rodents and flies traveling from kennel to kennel! Dogs may carry the virus on their fur and feet even if they themselves do not get ill. The virus enters the dog through the nose or mouth and has an incubation period of 3 days to 2 weeks.
5. Puppies under 6 months old are most likely to get severe disease. Rottweilers, Dobermans, pit bulls and mixes of these breeds are especially vulnerable. Adult dogs may get mild disease that is indistinguishable from diarrhea of any other cause. Affected dogs have mild to severe diarrhea, may be dehydrated and lethargic, have vomiting, or can develop severe to fatal secondary bacterial infections.
6. Vaccination usually prevents disease in adult dogs that have received a vaccine at least 1-2 weeks before exposure, but does not prevent them from carrying virus on fur if exposed. Puppies up to 16 weeks of age may not be protected fully by vaccination.

Diagnosing Parvovirus

There are three ways to "test" for parvo: clinical, by complete blood count (CBC), and by fecal antigen tests.

Clinically: Dogs with parvoviral enteritis typically have vomiting and diarrhea which typically is severe but may be mild. Lymph nodes may be enlarged and the dog may have a fever. Other diseases may mimic parvo, so a clinical diagnosis made without the aid of diagnostic testing is not precise.

CBC: Dogs with parvo typically have very few white blood cells. If the normal lower limits for white blood cell counts on the CBC is 6000 cells/microliter, a dog with parvo may have less than 1000. Although this also does not confirm parvo, it is strong evidence and a dog with some other disease and such a low white cell count requires aggressive treatment or euthanasia regardless.

Fecal antigen test: The fecal tests used in clinics and shelters are assaying for antigens of the virus itself. If the dog has the virus in its feces, the test should be positive. Always keep in mind that:

• Tests must be performed exactly as the literature indicates or the test is invalid.
• Tests should be performed on any dog with diarrhea that is also exhibiting signs of systemic disease: vomiting, lethargy, fever, loss of appetite, dehydration, or dogs with unusually copious, smelly/bloody diarrhea, or any dog with known exposure to parvo within the preceding 14 days who then develops diarrhea.

Interpreting test results

• Some vaccinated dogs may have a false-positive test, i.e. the virus in their feces is vaccine strain. The vaccine-positive result can happen within about 3-14 days of vaccination. A study in kittens suggests this is uncommon with some tests - only 1/64 recently vaccinated kittens tested weakly positive on the Idexx brand test. However, 13/64 kittens tested positive, some strongly positive, on the Synbiotics brand test. (Levy, J. K. (2006). Impact of Vaccination on Parvovirus Testing in Kittens. International Veterinary Vaccines and Diagnostic Conference, Oslo, Norway.) Equivalent data is not available for puppies, however all puppies testing positive should be carefully isolated regardless of recent vaccine history.
   
• Some dogs with parvo have negative tests, either because it is very early in the course of the disease or late in the course (most puppies will test negative by the time they've had clinical signs for 2-3 days). Tests should be repeated on dogs that are strong suspects or used in conjunction with a CBC or blood smear.

• Parvovirus is very uncommon in dogs over four months of age vaccinated at least 1-2 weeks prior to exposure. Positive test results in these dogs should be verified by another test, such as a CBC (or necropsy if the dog dies or is euthanized).

   

  Helpful test
  Thursday, March 13, 2008

  Pros: quick results

  Cons: results can be skewed if dog recently vaccinated
   
   

   

  Folks at our shelter have used this for dogs that have come in & may be going on transports. They have found the test helpful because you get a result quickly, but the results may not be accurate if the dog was recently vaccinated. It is a useful test over all though.

  Hopefully Negative!
  Saturday, March 15, 2008

  Pros: If positve can start treatment

  Cons: sometimes get false positives
   
   

   

  Used to tell owners if their dog is positve for parvo and if so treatment can be started right away. The early parvo gets treated the better the outcome usually.

  Stop the spread...quickly
  Friday, March 7, 2008

  Pros: gives diagnosis quickly

  Cons: not always accurate
   
   

   

  These parvo snap tests are a great way to try to determine the presence of parvo and help to stop the spread of the disease. The test is not 100% accurate though as sometimes there can be false positives if the dog/puppy has been recently vaccinated.

  

   

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