Canine Parvovirus

What is Parvovirus?

Parvovirus, often called “parvo” is an extremely contagious virus that infects dogs and causes severe gastrointestinal (GI) illness. Puppies under 4 months of age and adult dogs who have not received vaccines are most at risk from parvovirus.  The virus is spread by contact between a dog’s oral or nasal cavity and the feces of a dog infected by the virus.  Parvovirus can also be contracted through contact with infected surfaces, such as bowls, bedding, and even outdoor areas where infected dogs have been housed. The parvovirus is tough, and can live for months in soil or on surfaces if not properly disinfected. 

What Does Parvovirus Look Like?

Once a dog has come into contact with the virus, it takes three to seven days before any signs or symptoms are seen. Not all dogs that come into contact with the virus will be infected; puppies are the most vulnerable because their immune systems are not yet fully functional.  The virus attacks the cells which line the length of the intestines, causing the infected dog to have large amounts of vomiting and diarrhea, which is often bloody. This leads to severe dehydration and shock. Parvovirus also attacks white blood cells, which reduces the dog’s ability to fight further infections. As the illness progresses, the intestines’ ability to prevent bacteria from entering the blood stream decreases, which can lead to infection of the blood stream, called sepsis. Many infected puppies die within 48 to 72 hours if untreated, so a puppy (or adult dog) showing signs of severe vomiting, diarrhea, dehydration, lethargy and loss of appetite should be seen by a veterinarian immediately. 

How Does a Veterinarian Diagnose and Treat Parvovirus?

If a dog is suspected of having parvovirus, the veterinarian will often order a virus-specific ELISA test to look for antibodies to the virus. A small swab is taken from the dog’s rectum, and is added to a color-changing test. A color change at the test site indicates a positive result; the more pronounced the color change, the more antibodies are present.  Since false positives or negatives are possible, veterinarians will often order a complete blood count (CBC) for confirmation. This test takes a small amount of blood and looks at the dog’s blood cells. A low white cell count is often seen with dogs that are infected with the virus. This result, along with a positive ELISA test, gives the veterinarian confidence in the diagnosis of parvovirus. 

Treatment for the virus mainly consists of supporting the dog through the course of the illness; there is no specific cure for parvovirus. Infected dogs must often be hospitalized in an isolated area, to prevent the transmission of the virus to other dogs.  The fluids and electrolytes lost from vomiting and diarrhea must be replaced, often with the use of an IV (intravenous) drip.  Medications to stop or combat vomiting, nausea, and diarrhea are given, and the dog is kept warm and clean. As soon as possible, intake of food is encouraged, as this helps to minimize the loss of cells in the intestine.  Treatment should be started early, and should be aggressive to give the infected dog the best possible chance of survival. Even if these guidelines are followed, some dogs may die, but successful outcomes may approach 90% if proper treatment is initiated. 

How Can Parvovirus Be Prevented?

Proper vaccination of both puppies and adult dogs is of the utmost importance in preventing parvovirus infection.   Starting at 6 weeks of age, puppies should receive a combination shot (which vaccinates against parvovirus, distemper, adenovirus, and parainfluenza) every 3 to 4 weeks until they are at least 16 weeks of age. The vaccine should be boostered 1 year later, then every 1 to 3 years for the life of the dog.

Puppies should be kept away from areas where large groups of dogs can be found, such as kennels, doggy day cares, dog parks, and pet-friendly stores, until they are finished with their puppy vaccines at 16 weeks of age.  Adult dogs should receive yearly exams and vaccine boosters as often as recommended by a veterinarian. Dogs should not be taken to homes or areas where ill dogs have been housed. Though there is a slight chance puppies or dogs can still contract the virus in spite of these efforts, following these guidelines will dramatically decrease the chance that infection will occur.

Written by, Sarah Pavlina-Whelehan, LVT, VTS (ECC)

Clinical Educator at VSES