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Canine parvo viral disease complex in dogs is caused by infection with parvo. The main source of the virus is the feces of infected dogs. The stool of an infected dog can have a high concentration of viral particles. Susceptible animals become infected by ingesting the virus. Subsequently, the virus is carried to the intestine where it invades the intestinal wall and causes inflammation. Specifically, parvo virus invades the crypt cells if the intestine, that normally are responsible for absorption of nutrients.

Unlike most other viruses, parvo virus is stable in the environment and is resistant to the effects of heat, detergents, and alcohol. Parvo virus has been recovered from dog feces even after three months at room temperature. Due to its stability, the virus is easily transmitted via the hair or feet of infected dogs, contaminated shoes, clothes, and other objects. Direct contact between dogs is not required to spread the virus. Dogs that become infected with the virus and show clinical signs will usually become ill within 7-10 days of the initial infection.

The clinical signs of canine parvo viral disease can be variable, but generally take the form of severe vomiting and diarrhea. The diarrhea may or may not contain blood. Additionally, affected dogs often exhibit a lack of appetite, depression, and fever. It is important to note that many dogs may not show every clinical sign, but vomiting and diarrhea are the most common signs; vomiting usually begins first. Parvo may affect dogs of all ages, but is most common in dogs less than one year of age. Young puppies less than five months of age are often the most severely affected and the most difficult to achieve resolution.

The clinical signs of parvo virus infection in dogs can mimic other diseases causing vomiting and diarrhea. As a result, the diagnosis of parvo can be a challenge for the veterinarian. The positive confirmation of parvo virus infection in dogs requires the demonstration of the virus in the stool or the detection of anti-parvo virus antibodies in the blood serum. Occasionally, a dog will have parvovirus but test negative for virus in the stool. Fortunately, this is not a common occurrence. A tentative diagnosis is often based on the presence of a reduced white blood cell count (leukopenia). If further confirmation is needed, stool or blood can be submitted to a veterinary laboratory for the other tests. The absence of a leukopenia does not always mean that the dog cannot have parvo virus infection. Some dogs that become clinically ill may not necessarily be leukopenic.

Prognosis for dogs infected with parvo is guarded to fair, with best recovery rates
attained when aggressive treatment is utilyzed and therapy is begun before severe septicemia (blood born infection), severe dehydration, and leukopenia occur. Prognosis tends to be poor when the whilte blood cell count falls below 1000. For reasons not fully understood, some breeds, notably the Rottweiler, have a much higher fatality rate than other breeds.

The best method of protecting your dog against parvo virua infection is proper vaccination. Puppies receive a parvo vaccination as part of their multiple-agent vaccine given at 6, 9, and 12 weeks of age. After the initial series of vaccinations when the dog is a puppy, all dogs should be boostered after the first year, then once every three years thereafter. See our vaccine info page for more about parvo virus and other vaccines. The final decision about a proper vaccination schedule should be made by your veterinarian.

Given the stability of parvo virus in the environment, it is important to properly disinfect contaminated areas. This is best accomplished by cleaning food bowls, water bowls, and other contaminated items with a solution of one cup of chlorine bleach in a gallon of water ( 4 to 8 ounces of bleach in a gallon of water OR 250 mL in 4 liters of water). It is important that chlorine bleach be used because most disinfectants will not kill the canine parvo virus.


By: Roger L. Welton, DVM
Founder, Web-DVM
President, Maybeck Animal Hospital
Author Canine and Feline 101

16 thoughts on “Parvo

  1. Faith says:

    Can a puppy test positive if he had a parvo shot 5 days before the parvo test?

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