Canine Parvovirus: Symptoms, Causes, Treatment

A serious infectious disease, parvo first emerged in dogs in the 1970s. It causes significant morbidity and mortality and is especially dangerous to young unvaccinated dogs. The disease is characterized by severe vomiting and diarrhea and loss of normal immune function. While fairly easy to prevent and diagnose, parvo is often difficult to treat. If they are to recover, infected dogs usually require aggressive supportive care in a hospital setting.

What is Parvo in Dogs, and What Causes It?

Parvo is a life-threatening infectious disease caused by infection with the canine parvovirus, which is commonly called CPV. Dogs contract CPV when they eat infected feces, lick contaminated surfaces or lick their fur after having contact with contaminated surfaces.


After exposure, the virus begins to replicate in the lymph nodes of the throat and then enters the bloodstream. Once in the bloodstream, it spreads to various organs. CPV typically targets the rapidly dividing cells of the gastrointestinal tract and bone marrow. Damage to these tissues weakens the immune system and causes severe gastroenteritis. The resulting damage to the intestines allows intestinal bacteria to enter the bloodstream, and the lack of immune activity means that these bacteria can replicate unchecked. This can result in sepsis.

Dogs begin to shed virus particles in their feces about four days after exposure, and they continue to shed virus particles for the entire course of the illness and for about 10 days after symptoms cease. CPV particles are small and extremely hardy. They are resistant to many common disinfectants and can survive in a kennel environment for months to years. Once in the environment, the virus is extremely contagious. Unvaccinated and incompletely vaccinated dogs are most vulnerable to infection.

What Are the Symptoms of Parvo in Dogs?

The clinical signs of parvo usually begin three to seven days after exposure to the virus. Parvo symptoms in dogs are often vague at first and progress to severe vomiting and hemorrhagic diarrhea within 24 to 48 hours. Commonly reported symptoms include the following:

  • Fever.
  • Lethargy.
  • Loss of appetite.
  • Vomiting.
  • Profuse bloody diarrhea.
  • Collapse.

Parvo symptoms in puppies and dogs with weakened immune systems tend to be more severe than parvo symptoms in healthy adult dogs.

How is Parvo Diagnosed?

If a puppy or dog with an uncertain vaccination history presents to a clinic with severe diarrhea, the treating veterinarian is likely to be highly suspicious that the dog has parvo and institute quarantine procedures immediately. A simple fecal test can confirm CPV infection in most cases. Because false negatives and positives can occur, however, the veterinarian may recommend further testing if the results of the fecal test do not agree with the clinical presentation.

How is Parvo Treated?

Treatment for parvo is supportive and varies based on the severity of the disease and the symptoms of the individual dog. Effective treatment requires hospitalization and commonly includes the following medications and supportive measures:

  • Anti-nausea medications.
  • Intravenous fluids.
  • Injectable antibiotics.
  • Nutritional support.

According to a 2004 article in the Journal of Veterinary Emergency and Critical Care, survival rates for infected dogs approach 80 to 95 percent with aggressive therapy in a veterinary hospital. Without treatment, mortality rates are as high as 91 percent.

How Can Parvo in Dogs Be Prevented?

Modern vaccinations are extremely effective at preventing CPV infection. Current vaccination recommendations from the American Animal Hospital Association advise veterinarians to vaccinate dogs for parvo according to the following schedule:

  • A dose every three to four weeks for puppies between the ages of six and 16 weeks.
  • One dose for unvaccinated puppies and dogs over 16 weeks of age.
  • A booster dose one year after the initial vaccination or series.
  • One dose every three years after the one-year booster dose.

In addition to vaccination, prevention of parvo requires infection control. Owners should take care to keep unvaccinated and incompletely vaccinated dogs away from dog parks and other places where they could be exposed to the virus. Also, owners who have cared for infected dogs should thoroughly disinfect their homes with a solution of one part bleach and 30 parts water. Additionally, they should avoid bringing new puppies or unvaccinated dogs into their homes for at least one month after the infected dogs have left or recovered.

What Are Some Other Resources for Learning About Parvo in Dogs?