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What is Parvo?

Canine parvovirus (CPV) infection is a relatively new disease that first struck the canine population in 1978. Because of the severity of the disease and its rapid spread, CPV has aroused a great deal of public interest. The virus that causes the infection is very similar to feline distemper and the two diseases are almost identical. Therefore, it has been speculated that the canine virus is a mutation of the feline virus; however, that has never been proven.

Canine Parvovirus Infection (CPV) is considered most threatening to puppies between the time of weaning and six months of age. Adult dogs can also contract the virus, although it is relatively uncommon. Keep in mind that there is more than one strain of parvo, so your animal can get the virus again.

CPV affects only dogs and cannot be transmitted to humans or another species. However, other animals and humans can carry it to dogs. Dogs that become infected have a 50-50 chance of survival. If they survive the first four days, they will usually recover rapidly and become immune to the virus for life. Most puppies will die without medical treatment.

Once your animal recovers, continue with vaccinations on a recommended schedule through the four shot protocol.  Many parvo puppies have gone on to live normal lives with no further complications.   

Canine parvovirus has been reported to exist in approximately 50 different countries.


The causative agent of CPV disease is a very hearty virus. like other viruses, CPV is stable in the environment and is resistant to the effects of heat, detergents, and alcohol. CPV has been recovered from dog feces even after three months at room temperature.

Since the virus is so resistant to decay, it can survive for long periods and be transmitted to any dog by simple contact with a contaminated object (called a “fomite”). Examples of fomites include shoes, clothing, play toys, insects, and feet of the infected dog.

Feces of the infected dog contain millions of viral particles. Susceptible dogs become infected by ingesting (swallowing) the virus. There does not have to be direct contact between the two dogs. Dogs that become infected with the virus and show clinical signs will usually become ill within seven to ten days of the initial infection.

Contributing Factors:

Several factors contribute to the clinical course of parvovirus infection in dogs. These include stress, vaccination history, and age of the dog, concurrent infection with other diseases or parasites, and breed of the dog.

Various studies have reported the breeds thought to be at increased risk for parvovirus; these breeds include the Rottweiler, Doberman pinscher, black Labrador Retriever, American Pit Bull Terrier, and the German Shepherd dog.

Parvoviral enteritis (intestinal inflammation) 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 treat.

CPV has been regarded as reaching peak incidence in the spring and summer months, when puppies are losing the natural immunity conferred from the mother. A 1996 study of 283 dogs with CPV found the highest incidence in July, August, and September. Intact (non-neutered) male dogs were more likely to contract CPV than female dogs.

Does parvovirus pose a health risk for me? How about for my cats?

At the present time, there is no evidence to indicate that CPV is transmissible to cats or humans.

Dogs that spend their time confined to a house or yard and are not in contact with other dogs have much less chance of exposure to CPV. It's easily transmitted via the hair or feet of infected dogs, and also by contaminated objects such as cages or shoes. CPV is hardy and can remain in feces-contaminated ground for five months or more if conditions are favorable.

Although most disinfectants cannot kill it, chlorine bleach is quite effective. There may be other means of transmission of CPV, but they are not known at this time.

Diarrhea syndrome, or enteritis, has an incubation period of five to fourteen days.

Dogs with enteritis act like they are in extreme pain.

Early symptoms are depression, loss of appetite, vomiting, high fever, and severe diarrhea. Feces can be either grayish or fluid and bloody. Rapid dehydration is a danger, and dogs may continue to vomit and have diarrhea until they die, usually three days after onset of symptoms.

Others may recover without complications and have no long-term problems. Puppies can die suddenly of shock, as early as two days into the illness.

Can parvo be prevented?

The best method of protecting your dog against CPV infection is proper vaccination. Puppies receive a parvo vaccination as part of their multiple-agent vaccine given at eight, twelve and sixteen weeks of age. In some situations, veterinarians will give the vaccine on two-week intervals and an additional booster at 18 to 20 weeks of age.

After the puppy series of vaccinations, all dogs should be bolstered at least once a year. Dogs in high exposure situations (kennels, dog shows, field trials, etc.) may be better protected with a booster every six months.

Pregnant bitches should be bolstered within two weeks of whelping in order to transfer protective antibodies to her puppies.

The final decision about a proper vaccination schedule should be made by your veterinarian.

Long Term Prevention:

Ideally, four shots are given three to four weeks apart starting at six to eight weeks. Best protection rates seem to be with the distemper/parvo only “Puppy” shots.  The five-way may over work the immune system, but they are better than nothing and it is what most vets use.  Some vets do the final or fourth shot once the animal has reached six months of age.

Is there a way to kill the virus in the environment?

The stability of CPV in the environment makes it important to properly disinfect contaminated areas. This is accomplished by cleaning food bowls, water bowls, and other contaminated items with a solution of 1/2 cup chlorine bleach per gallon of water. It is important that chlorine bleach be used because most "virucidal" disinfectants will not kill canine parvovirus.  

NOTE FROM BOSTON TERRIER NETWORK: The information on Canine parvovirus (CPV) infection better known as PARVO is from several sources, meant to introduce you to a very serious virus that usually affects dogs under the age of two years old. We feel that anyone working with dogs of any breed or age should be aware of this virus and the preventive measures to reduce risks.

Related articles:

Dogs under the age of two years old are the most at risk of becoming infected with Parvo.
PARVO, Home Treatment for Parvo
PARVO, Keeping the virus from spreading