Canine Parvovirus: What You Need To Know

Medical Articles

Barbara Sorg did everything right. So how did she end up with a $15,000 veterinary bill? Despite taking every precaution, her litter of eight-week-old English Shepherd puppies was infected with the canine parvovirus (CPV). Each puppy spent varying amounts of time in the intensive care unit, with four of them surviving and one being humanely euthanized. "I have no idea where they picked up the parvo," Sorg says. "I assume it came in on one of the shoes of the many visitors, or the shoes of prospective puppy buyers, as the puppies were only on my property. It could have come in on one of my family members' shoes, or it could have been brought to my yard by an infected raccoon. We will never know."

Experts say CPV particles are literally everywhere in every environment—except those environments that are regularly disinfected (highly resistant to most cleaning products, contaminated areas, such as floors, walkways, driveways, crates, etc., can be disinfected with one part bleach to 30 parts water). Even then, sterile environments can be quickly re-infected, as the virus is shed in large amounts in the stools of infected dogs for several weeks following infection and can be carried on a dog's feet and hair, as well as carried on shoes, clothing, tires, pet crates, and other animals. To make matters worse, CPV is extremely hardy and viral particles are capable of surviving for months in the environment—even through winter.

A Bit of History

Nearly every mammal species, humans included, has its own parvovirus, with each virus being specific for which animal it can infect. For instance, the pig parvovirus will not infect people, the canine virus will not infect cats, the human virus will not infect dogs, etc.

The original canine parvovirus, discovered in 1967 and called CPV-1, did not represent much threat - except to newborn puppies. Experts believe it mutated from the already well-known feline panleukopenia virus (FPV). Around 1978, a new variant, CPV-2 emerged and no dogs had immunity against the virus, which resulted in a CPV epidemic. By 1979, a second virus—CPV-2a—emerged, which seemed even more aggressive. In 2000, yet another virulent strain known as CPV-2c was discovered in Italy, with the first case in the United States being confirmed in 2006.

How Parvo Works

Infection occurs when a puppy or adult dog ingests the virus. To successfully infect a dog, CPV needs the help of rapidly dividing cells, with the first cells to be attacked being the lymph nodes of the throat. Incubating there for a few days, the virus then spills into the bloodstream—traveling to the bone marrow and intestinal cells. Within the bone marrow, CPV destroys white blood cells—making it easier for viral particles to invade and wreak havoc on the gastrointestinal (GI) tract. A dog's intestines have rapidly dividing cells, and it's here where CPV does the most damage--leaving a puppy's intestines unable to absorb nutrients. Eventually, bacteria, which is normally confined to the GI tract, spills out of the intestines and into the bloodstream—causing significant blood loss through diarrhea and widespread infection throughout the puppy's body.


Severe diarrhea (oftentimes odorous or bloody) and nausea (which further weaken a puppy's system) are the primary symptoms. Lethargy, depression, loss or lack of appetite, followed by a sudden onset of high fever may also occur. The typical incubation period is 3 to 7 days between initial infection and onset of first symptoms.

Diagnosis, Treatment, and Prognosis

This highly contagious gastrointestinal disease normally affects puppies, but unvaccinated dogs of all ages are susceptible. For unknown reasons, some breeds are at a higher risk of infection including RottweilersDoberman PinschersLabrador RetrieversAmerican Staffordshire Terriers, and German Shepherd Dogs.

Diagnosis is confirmed with an enzyme-linked immunosorbent assay (ELISA) test, with results being available in about 15 minutes.

Treatment consists of intensive veterinary management including intravenous fluids to control dehydration, and antibiotics for infection, which requires a costly hospital stay. Oftentimes, the cost is prohibitive for many owners, with euthanasia being the alternative for severely affected puppies.

CPV is not always fatal, but those dogs who die usually do so as a result of dehydration and/or secondary bacterial infection.

New Protocol

The typical cost for inpatient care ranges between $1,500 to $3,000, with an average hospital stay being 5 to 7 days. However, researchers at Colorado State University Veterinary Teaching Hospital have developed an alternative treatment—intensive at-home care at a fraction of the cost. The treatment relies on two drugs recently released by Pfizer Animal Health. Maropitant, a strong anti-nausea medication, which is given under the skin once a day, and Convenia, an antibiotic given under the skin once and lasting two weeks, as well as subcutaneous fluids three times a day. While results are still being compiled, early numbers from CSU indicate an "85 percent survival rate for the outpatient group, compared to a 90 percent survival rater for the inpatient group."

Preventing Parvo

Parvo is a highly contagious and often lethal gastrointestinal disease. To keep your puppy safe, experts recommend the following:

  • Vaccinate your puppy. Puppies have immunity from their mother early in life, but should receive their first vaccination between 6 and 8 weeks of age and then two boosters at three-week intervals. Many experts recommend the final vaccination occur at 16 weeks of age to avoid maternal antibody interference.

  • Avoid taking your puppy to high-risk areas such as dog parks, pet stores, doggie day care, boarding kennels, and other areas dogs frequent until the puppy has received its complete set of vaccinations.

If you suspect your dog has been exposed or shows symptoms including vomiting or diarrhea, seek veterinary attention immediately. Time is of the essence.