Canine parvovirus, or “parvo” as it is commonly called, is one of the most significant health threats to dogs, especially puppies. It is also the cause of much confusion among new pet owners. So, what is parvo?

What is canine parvovirus?

Parvovirus is a highly contagious and often fatal virus that attacks dividing cells (mainly in the bone marrow and intestines).

During a parvo infection, rapidly dividing cells, such as intestinal cells and bone marrow cells, are targeted by the virus. Viral attack of these cells results in debilitating diarrhea, as well as a drop in the defensive white blood cells usually produced by a puppy’s bone marrow to combat this type of infection.

With parvovirus, a puppy can become fatally dehydrated, or if the intestinal walls become damaged, bacteria can cause septic infection of the blood. Every year we receive pet insurance claims at Petplan for puppies and dogs who were infected with parvovirus and became gravely ill. Scary, right?

Preventing parvovirus in pets

Timely vaccination is key in preventing parvovirus infection.

Work with your veterinarian and their team to make sure that any dog that you adopt or buy has had the appropriate vaccines and is scheduled to receive the their boosters. Responsible breeders and shelters will have records of all of the vaccines that pets have received while in their care. Once your pet is vaccinated, ensure that your veterinarian boosts your pet's vaccines (usually every three years for pets 2 years and older) or performs annual tests to ensure your pet has adequate immunity to parvovirus.

There is a brief period before a puppy reaches 16 weeks where there is a “switchover” between antibodies from the mother and effective vaccine protection. During this switchover time, any puppy can be vulnerable. For this reason, veterinarians recommend puppies under 16 weeks avoid any “potentially contaminated areas.”

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How do dogs get parvovirus?

Since the virus has been around for such a long time and because it’s so hardy, the safest assumption to make is that it can be everywhere outside of areas that you can clean and disinfect yourself. That means pet stores, sidewalks, puppy training classes, and even other dogs pose potential risks for young or unvaccinated puppies. It’s best to restrict your puppy from public outdoor areas until he’s at least 16 weeks old and has received his full canine parvovirus vaccination regime.

Obviously, infected dogs are the most virulent source of infection, but this resilient virus can live for long periods of time in conditions from extreme heat to freezing cold. Thus it’s important to wash clothes and shoes that may have been exposed to the virus to prevent contaminating new environments (i.e. your house!).

Most vets will take the time to inform new pet parents about the dangers and symptoms of parvovirus for their new puppies. Considering that the majority of deaths from parvo occur in just 48-72 hours from the first sign of symptoms, immediate veterinary care is essential to save a dog’s life.

Common parvovirus symptoms include:

  • Lethargy
  • Refusal to eat
  • Fever
  • Vomiting
  • Severe bloody diarrhea
  • Dehydration

If you suspect that your puppy has parvo, your veterinarian will likely confirm the diagnosis with a specialized fecal test. To date, no mainstream medications exist to combat the virus directly, so your vet will give supportive care to treat against the two main risks: dehydration and systemic bacterial infection.


The mainstays of parvovirus treatment are intravenous fluid therapy and antibiotics, both of which can be required for many days. To avoid the risk of exposing other dogs to the virus, infected pets are held in an isolation unit during treatment. Infected dogs should also have their toys, bowls, bedding and accessories disinfected with a bleach mixture (one part bleach to 30 parts water).

Sep 17, 2009
Pet Health

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