Health

Parvovirus Infection (Canine)

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Parvoviral enteritis (or parvo) is a viral disease that affects young, unvaccinated dogs between 6 weeks and 6 months of age. It attacks rapidly dividing cells in the intestinal tract and bone marrow, causing severe vomiting, diarrhea, impaired immune function and sometimes death.

Common name: Parvo
Scientific name: Canine parvoviral enteritis

Diagnosis

Signalment
Any unvaccinated dog is susceptible to contracting parvoviral enteritis; however dogs between the ages of 6 weeks and 6 months are especially susceptible. Breeds at increased risk include Rottweiler, Doberman pinscher, Labrador retriever, American pitbull terrier, American Staffordshire terrier, German shepherd and Alaskan sled dogs.

Incidence/prevalence
Parvovirus particles can be found everywhere in the environment. They are hardy and can survive for five months or more. Infected dogs shed the virus in their feces, and infective virus particles can be found in grass, on concrete and anywherean infected dog has defecated. The virus is highly contagious and can be transmitted from infected dogs to susceptible dogs through ingestion, nasal exposure or fomites (humans, clothing, bedding, bowls).

Geographic distribution
Canine parvovirus is found throughout the United States, Europe, the Far East and Japan. Different strains are prevalent in different regions.

Clinical signs (primary, most to least frequent, scientific term, synonyms)
Severe vomiting, inappetance, diarrhea (with or without blood), rapid dehydration follows , Lethargy, decreased activity, Fever (sometimes very sick animals have a low temperature), Secondary infection and sepsis, Sudden death.

Clinical signs (secondary, most to least frequent, scientific term, synonyms)
Intussusception (the telescoping of one segment of intestine into another), Clotting disturbances, Neurologic signs, Ulceration of skin, mouth, footpads.

Causes (scientific, common term)
Canine parvovirus strains 2a, 2b and 2c, Canine parvovirus-1 (less common).

Organ systems affected (most to least affected)
Gastrointestinal tract, Cardiovascular system, Central nervous system, Skin.

Diagnostic tests
Fecal ELISA test for viral antigen (virus particles), Complete blood count (can corroborate clinical suspicion), Differential Diagnosis, Dietary indiscretion, causing gastroenteritis, Foreign body ingestion, Intestinal parasitism, Pancreatitis, Other viral and bacterial diseases, Endocrine diseases such as hypoadrenocorticism (Addison's disease).

Overview

Parvovirus is a serious, life-threatening viral disease affecting young dogs that have not had a complete set of vaccinations (see prevention section, below). The virus is hardy, can be found everywhere in the environment and survives many common household disinfectants. Parvovirus is highly contagious and is spread through oral-nasal or fecal-oral routes.

The virus can survive in cages, on food and water dishes, and can also be transmitted by human beings on hands and clothing. There is usually a one- to two-week period in which the pet shows no signs (incubation period) – they can be shedding the virus in their feces before showing any signs of infection.

The virus attacks rapidly dividing cells – the lining of the intestine and the bone marrow. Infected dogs have vomiting and diarrhea with or without blood, and severe dehydration soon results. Because the lining of the intestine is destroyed, bacteria in the intestines gain access to the blood. The virus also destroys white blood cells, which help fight infection. The loss of white blood cells combined with the bacteria in the bloodstream contributes to blood infections.

Some dogs develop myocarditis (inflammation of the heart), clotting disturbances and neurologic signs usually secondary to bleeding in the brain or hypoglycemia (low blood sugar). Because of the low white blood cell count that accompanies parvovirus, it is not uncommon for dogs to develop urinary-tract infections or IV-catheter-site infections.

Treatment

Professional Care
The diagnosis of parvoviral enteritis is based on signalment (age and breed), an incomplete or absent vaccination history, clinical suspicion, a positive ELISA antigen test and a low white blood cell count. The ELISA fecal antigen test is diagnostic; however, a negative test does not rule out infection due to the short period of fecal shedding. Pets recently vaccinated (5 to 12 days post-vaccination) may yield false-positive test results; however, the reaction is typically weak positive. Other causes of vomiting and diarrhea, such as foreign-body ingestion, should be ruled out.

Hospitalization is critical for success. Since the disease is viral, treatment is largely supportive. Intravenous fluids and antibiotics are the cornerstone of treatment – these are used to fight the systemic infection that results from loss of the intestinal lining and low white blood cell count. Antiemetic drugs are given to lessen vomiting.

Sometimes plasma is needed to replace proteins lost to diarrhea as well as to provide clotting factors. Plasma has the added benefit of providing antibodies to the virus if it has been taken from a recently vaccinated dog. Antiviral therapies are being studied but are not routinely used at this time.

Home Care
The virus is extremely hardy and resistant to common household disinfectants. The exception is household bleach, a solution of one part bleach to 30 parts water for at least 10 minutes will inactivate the virus. Recovering dogs should be isolated from other dogs as well as from cats, it has been shown that canine parvovirus is transmissible to cats. Fecal shedding can occur for up to 10 days. All feces should be disposed of and the area should be treated for 10 minutes with the dilute bleach solution.

All living areas, bedding, food and water dishes and toys should be either disposed of or cleaned with the bleach solution. Be sure they are washed thoroughly with soap and water before reuse. Although canine parvovirus has not been shown to infect humans, many dogs have concurrent parasitic or viral infections, and proper hygiene should always be used when handling fecal materials.

Dogs recovering from natural infection are typically immune to reinfection for up to 20 months and potentially for life. It is still highly recommended that they receive their regular immunizations, as the disease is easily prevented with proper vaccination.

Action/Prevention
Proper vaccination has been shown to be protective against parvoviral enteritis. Starting between 6 and 8 weeks of age, puppies should receive a modified-live virus vaccine every three to four weeks, until they are 14 to 18 weeks of age. They should receive a booster vaccine one year following their last puppy vaccine and every three years thereafter. Puppies that have not completed their entire series of vaccines should not be walked outside until they are fully immunized.

Outcome
If caught early, puppies typically recover from infection with appropriate supportive care; however, sudden death is possible. Young animals, animals with a low white blood cell count and Rottweilers typically have a poorer prognosis.

References/Additional Readings

Greene, Craig E. Infectious Diseases of the Dog and Cat. St. Louis, Missouri: Elsevier, 2006; 63-70.

Author

Sarah K. Alward, DVM

Editor

Steven Hansen, DVM, MS, MBA, DABVT, DABT

© 2007. The American Society for the Prevention of Cruelty to Animals (ASPCA)

Please note that PetVet should only be used as a guide and in no way should be substituted for licensed veterinary care.

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