What is Canine Parvovirus?

Parvovirus is a viral disease of dogs. It affects unvaccinated dogs, typically as young puppies. The virus grows in rapidly dividing cells. The intestinal lining has the greatest concentration of rapidly dividing cells in a puppy's body. The virus attacks and kills these cells, causing diarrhea (often bloody), depression and suppression of white blood cells -- which come from another group of rapidly dividing cells. In very young puppies it can infect the heart muscle and lead to sudden death. Chance of survival with no treatment is less than 10% and depends on age and weight.


"Parvo" is a virus that attacks the lining of the digestive system. It causes dogs and puppies to not be able to absorb nutrients or liquids. Puppies are especially prone to it because they have an immature immune system. When dogs and puppies contract Parvo, they often have diarrhea, vomiting and lethargy. Usually they stop eating and develop a bloody, foul-smelling, liquid stool. Symptoms usually begin with a high fever, lethargy, depression, and loss of appetite in the first 2-3 days of symptoms. Secondary symptoms appear for the next 3-5 days as severe gastrointestinal distress, such as vomiting and bloody diarrhea. In many cases, dehydration, shock, and death follow within 3-6 days of original symptoms occurring.


Canine parvovirus is shed in the feces of infected dogs, and a dog contracts it by swallowing some of that feces. This may seem unlikely, but if a dog gets infected feces on his paws and then licks them, he has swallowed the virus. The dog doesn't even have to step in a pile of dog poop, if a person steps in a pile, or even the remains of one that has been picked up that person would pick up a small amount of contaminated feces on her shoe and spread it wherever she steps. All a dog would have to do to contact the virus is step in the same place the person with the parvo-contaminated shoe stepped. Adult dogs may be infected carriers without showing any clinical signs. Dogs with the typical diarrhea that parvovirus causes shed the virus as well. It can last a long time in the environment, perhaps up to one year or even longer.

Generally, it takes 1-5 days from the time of exposure for dogs and puppies to start showing symptoms and to test positive for Parvo.

Parvo is highly contagious to unprotected dogs, and the virus can remain infectious in ground contaminated with fecal material for five months or more if conditions are favorable. The virus is extremely hardy; most disinfectants cannot kill it, including isopropyl alcohol and ammonia. Chlorine bleach is the most effective and inexpensive agent that works, and is commonly used by veterinarians.

The ease with which infection with Parvo can occur in any unvaccinated dog must be stressed. The virus is extremely hardy in the environment. Withstanding wide temperature fluctuations and most cleaning agents. Parvo can be brought home to your dog on shoes, hands and even car tires. It can live for many months outside the animal. Any areas that are thought to be contaminated with Parvo should be thoroughly washed with chlorine bleach diluted 1 ounce per quart of water.

Dogs and puppies can contract Parvo even if they never leave their yards. Parvo virus, despite what you might hear, is NOT an airborne virus. It is excreted in the feces of infected dogs, and if someone -- human, dog, bird, etc. -- steps in (or otherwise comes in contact with) the excrement, the possibility for contamination is great. Some people speculate that birds invading a dog's food dish can deposit the parvovirus there. If you think you may have come in contact with parvovirus, a 1 part bleach, 30 parts water solution does kill the virus, so you can wash your shoes and clothes, even your hands with it, to reduce the risk of infecting your dog. Rest assured that parvovirus is specific to dogs alone and cannot be transmitted to humans or other pets of a different species, such as cats.


Without intense treatment, the victims of Parvo die of dehydration and secondary bacterial infections. Treatment generally consists of IV or sub-cutaneous fluids and antibiotics. There is no cure. Veterinarians can only treat the symptoms palliatively, and try to keep the dog alive by preventing dehydration and loss of proteins and infection. As there is no cure for any virus, treatment for Parvo is mostly that of supporting the different systems in the body during the course of the disease. This includes giving fluids, regulating electrolyte levels, controlling body temperature and giving blood transfusions when necessary.


It can be very hard to successfully vaccinate a puppy for this disease because the antibody protection the puppy acquires from its mother can interfere with vaccination. Many vets recommend vaccinating puppies every three to four weeks for this virus starting at 6 weeks of age and continuing until they are at least 16 weeks of age and preferably 20 weeks of age. It is possible that this vaccine confers lifelong immunity once it does work but most veterinarians continue to recommend yearly vaccination for it. It seems prudent to at least get the vaccination at one year of age. Since it is combined with the other vaccines it is often easier just to give it yearly with them.