Canine Parvovirus: A Hidden Killer

They say that an ounce of prevention is worth a pound of cure, and in the case of canine parvovirus this could not be more true. First identified in 1978, canine parvovirus is a highly contagious virus that causes a potentially fatal gastrointestinal infection in dogs. The main victims of the virus are young puppies, and symptoms include vomiting, diarrhea (often bloody), lethargy, loss of appetite, and fever.

Puppies under 4 months of age, and adult dogs who have not been vaccinated, are most susceptible. Young puppies are most vulnerable when the protection provided by their mothers’ first milk, the colustrum, fades and the first round of puppy vaccinations for parvovirus has not begun. Additionally, the initial natural immunity provided by the mothers’ milk can actually interfere with early vaccinations when the mothers’ antibodies destroy the virus in the vaccine as if it were a real infection.

If contact leads to infection, the virus enters the puppy’s body when he ingests infected stool, and there is a 3-7 day incubation period before the puppy seems ill. Upon entry the virus first attacks the lymph nodes (a rapidly dividing group of cells) and replicates itself to large numbers. After several days, the volume of virus is such that significant amounts of it are released into the bloodstream. The pattern of seeking rapidly dividing groups of cells repeats, this time in the bone marrow and intestinal walls. In the marrow, the virus destroys immune system cells, destroying the body’s best defense, and heads for the gastrointestinal tract – the site of most serious damage. The bone marrow infection causes a drop in white blood cells; this indicator on a blood test could help with diagnosis.

The final blow of a parvovirus infection is the damage to the gastrointestinal tract, cutting off the puppy’s ability to absorb nutrients. Vomiting and diarrhea (in large amounts) result, combined with the breakdown of the barrier separating the digestive bacteria from the blood stream. The diarrhea then becomes bloody, and bacteria can enter the body freely, causing widespread infection. At this point, the poor puppy is struggling for life.

At this point, the best line of defense for the veterinarian is replenishing and support. The puppy needs fluids, and lots of them, administered intravenously to offset the terrible fluid loss caused by the vomiting and diarrhea. Antibiotics, given as shots or through the IV bag, counter the bacterial invasion triggered by the virus. Injections for nausea are also recommended to prevent further bouts of vomiting. Veterinary care is essential in the treatment of parvovirus infection; home care is not recommended. Sadly, experience says that if a puppy has not shown obvious improvement by the 4th day of treatment, he will not survive.

Parvovirus is a true villain in the canine world. It is incredibly tough to destroy, withstands extremes of temperature and other conditions, lives practically everywhere, and is spread easily through a myriad of means. Dogs and puppies can contract the virus through ingestion of fecal material of contaminated dogs, contact with infected food and water bowls, direct contact with contaminated dogs and by direct contact with caretakers who may carry the virus on their clothes and shoes.

One source says that a typical infectious dose for an unvaccinated dog is 1,000 viral particles; an infected dog sheds 35 million viral particles per ounce of stool (35,000 times the typical infection dose)! An infected environment can harbor the virus for months, depending on whether it is inside or out, and whether it can be thoroughly disinfected. Bleach is the best disinfectant against viruses, including parvo. But lawns and carpets, for example, are non-bleachable; it is recommended, though, that watering a lawn (if there is good drainage) may reduce the volume of virus. Contamination by active viral infection should be recognized in shady areas for 7 months, in sunlit areas for 5 months, and indoors for one month.

So, as good dog owners, we need to consider parvovirus as a deadly enemy of our best friends. Its infectious symptoms are preventable with vigilance (in stool cleanup – ours and others if necessary), vaccinations (for all dogs starting in puppy hood), staying current on the latest issues (new strains of virus, different vaccines, etc), and just being aware. You don’t need to experience parvovirus firsthand to know how devastating it can be. Just remember the dangers it poses to YOUR dog, and practice due diligence. Remember, an ounce of prevention is worth a pound of cure.

by Bettie Biehn

Bettie Biehn is a freelance writer, specializing in magazine articles, resumes and rhyming poems.