Parvovirus Infection in Dogs

What is Parvo?
Parvo is a common and potentially serious viral disease in dogs. The virus is officially known Parvovirus. The disease caused by this virus is commonly referred to as Parvo. The virus first appeared clinically in 1978, and there was a widespread epidemic in dogs of all ages. Since no dogs had been exposed or vaccinated (the vaccine didn't exist at the time), dogs of all ages died from the infection. The virus can "adapt" over time, and other strains of the virus have appeared since then, but properly administered vaccinations are the best protection. Canine Parvovirus is thought to be a mutation from the feline Parvovirus, also known as Feline Distemper virus.

What are the signs seen with Parvovirus infection?
There are three main manifestations of Parvovirus infection:

1. Asymptomatic - No signs seen. Common in dogs over 1 year old and vaccinated dogs.
2. Cardiac - This form of the disease is much less common than the intestinal form due to widespread vaccination. Severe inflammation and necrosis (cell death), of the heart muscle causes breathing difficulty and death in very young (less than 8 weeks of age) puppies. Older dogs that survive this form have scarring in the heart muscle.
3. Intestinal - This virus causes extreme damage to the intestinal tract, causing sloughing of the cells that line the tract. This can leave the patient open to secondary bacterial infection. Most of the affected dogs (85%) are less than one year old and between 6-20 weeks old -- before the full set of vaccinations can be given. The death rate from infection is reported to be 16-35% in this age group.*

The intestinal signs include:

• Lethargy
• Vomiting
• Loss of appetite
• Diarrhea - usually bloody, and very foul-smelling (a characteristic odor, particular to Parvovirus infection)
• Intussusception - when a section of the inflamed intestinal tract telescopes into itself. This is an emergency.
• Fever

The onset of clinical signs is usually sudden, often 12 hours or less. The incubation from exposure to seeing the clinical signs varies from 3 to 10 days.

How is Parvovirus infection diagnosed?
This disease is diagnosed by physical examination, signalment (age, vaccination status, breed, etc.), and a fecal Parvo (ELISA) test. Additional diagnostics include blood work and radiographs. Dogs infected with Parvo typically have a low white count. Radiographs help rule out other potential causes for vomiting and diarrhea.

How is Parvovirus infection treated?
There is no treatment specifically for the Parvovirus at this time. Treatment is supportive care, which includes any or all of the following:

• Oral electrolyte fluids - if the case is mild and the animal isn't vomiting
• Subcutaneous (SQ) or intravenous (IV) fluids to maintain hydration in the face of the extreme fluid losses from vomiting and diarrhea that are so typical with this disease
• Anti-vomiting/nausea medications - to prevent further damage from vomiting and to keep the patient comfortable as possible.
• Antibiotics - because the virus has potential to slough the intestinal tract, antibiotics help protect against secondary infection.
• Blood or Plasma transfusions - to replace protein loss, provide antibodies, help with anemia.

Many puppies infected with Parvovirus need to be hospitalized for supportive care. Hospitalization is typically about 5 days, sometimes longer. Surviving the first three days is usually a good sign for long term survival.

How long does Parvovirus last in the environment?
The Parvovirus family of viruses are particularly long-lived in the environment, lasting anywhere from 1 to 7 months -- commonly surviving 5-7 months in an outside environment. Due to the large amounts of virus particles shed in the feces of an infected dog (shedding lasts two weeks or more after exposure) and the longevity of the virus, complete eradication of the virus is often impossible.

How can I disinfect an area contaminated by a dog infected with Parvovirus?
There are many Parvovirus disinfectants on the market, but regular old bleach is still 100% effective against Parvovirus. The dilution for bleach is one part bleach to 30 parts water. Caution is advised for dyed or colored fabrics or objects. This should go without saying, but to be complete, DO NOT use a bleach preparation on the animal at any time!!! The commercial Parvovirus disinfectants have the advantage of better smelling preparations. Check the label for color fast warnings. See your vet or pet store for the various disinfectants available.

Be sure to keep feces (and any vomitus) picked up in the yard and kennel area as well.

How can I protect my dog from becoming infected?
Vaccination is the key to prevent this disease and protect your dog. Breeding bitches should be vaccinated prior to becoming pregnant to ensure that the pups get the best start at immunity. Vaccinations should start at 6 weeks of age, and be boostered at 9, 12, and 16 weeks of age. Some veterinarians also booster at 20 weeks, depending on the breed and Parvovirus risk in your area. Speak with your veterinarian about what vaccination protocol is the best for your pet and your lifestyle.

I heard that some breeds of dogs are more susceptible, is this true?
Yes, it appears that some breeds, most notably the Rottweiler, Doberman Pinscher, German Shepherds, Pit Bulls, and Labrador Retrievers are at an increased risk for this disease. Conversely, Toy Poodles and Cockers appear to be at a reduced risk for contracting this disease.** It is important to remember, however, that any breed can get Parvovirus. Be sure to keep your dog's vaccinations up to date.

** Breed information from The Merck Veterinary Manual, 8th ed.

Text: Copyright © Janet Tobiassen Crosby. All rights reserved. vetmedicine.about.com