Parvo Virus article by Dr. Jody McMurray D.V.M. ~ Dog Wellness

Here is an important and timely article by Dr. Jody McMurray (D.V.M., B.Sc. (Ag)) from her blog:

Parvo virus

Dear Dr. Jody:

We have seen on the news recently that there is a parvo outbreak in Calgary.  We have been avoiding off-leash parks since we heard about the outbreak, but what else can we do to keep our three year old Basset hound, “Porkchop”, safe from this disease?


Canine parvo virus, or CPV, has been making headlines in Calgary this fall.  Dog owners are right to be concerned about the illness, however, parvo has been around since the mid-1970s, and it usually does flare up every spring and fall in the Calgary area.  At my clinic in Cochrane, we have seen two cases of parvo in the past two months.  This is roughly the number of cases we would have expected for this time of year.

Parvo is a dangerous and highly contagious virus that is transmitted from dog to dog via the fecal-oral route.  This means that your dog has to ingest the virus in order to become infected.  Because the virus is shed in the stool of infected dogs, your dog could come into contact with the virus by walking in areas where infected dogs have defecated.  Once your pet licks his paws through routine grooming, he is potentially exposed.

Once inside your dog, the virus multiplies in the tonsils and other lymphoid tissues.  Within 3-5 days, the virus is cruising around inside your dog’s bloodstream, where it gains access to special cells that line the intestine, called crypt cells.  Six to ten days after exposure, your dog will begin demonstrating clinical signs of the illness.  These signs include inappetance, vomiting, watery and sometimes bloody diarrhea, and rapid dehydration.  Without prompt treatment, the illness is often fatal.  Infected dogs typically die from dehydration; however, because ill dogs have sustained damage to their intestinal walls, gut bacteria can gain access to the bloodstream.  This leads to sepsis which is fatal without treatment.

The most severe cases of parvo are seen in young puppies, since the virus has a particular affinity for the rapidly-multiplying intestinal cells found in growing animals.  Rottweilers, Doberman pinschers, pit bulls, Labrador retrievers, German shepherds, and Siberian huskies seem particularly susceptible to the illness.

Successful treatment of parvo depends heavily on attaining a prompt diagnosis.  The illness is straightforward to diagnose with a combination of a complete blood cell count and a fecal parvo test.  The fecal parvo test detects the presence of the virus in the stool, but because the virus is only shed during certain stages of the illness, your veterinarian may also rely on a blood test to help confirm the disease.  Because parvo virus shuts down the production of white blood cells in the bone marrow, your veterinarian may make a diagnosis of parvo virus based on a depressed white blood cell count.

It is partly due to this depressed white blood cell count that diseased animals become secondarily infected with bacteria.  Treatment of parvo virus therefore includes IV antibiotics.  Dogs suffering from parvo will also require several days of expensive, intensive care hospitalization with IV fluids, anti-nauseants, and occasionally, pain medication.  Treated early in the course of the disease, the prognosis for survival is good.  Dogs that have recovered from parvo virus can continue to shed the virus in their stool for several days or even weeks.  The virus is stable in the environment and can survive for long periods of time in the soil.  For this reason, it is, and always has been, critically important that puppies that have not completed their vaccine series are kept away from areas where other dogs may have defecated.

Puppies receive some immunity through their mother’s milk.  This immunity, called “maternal antibody”, is generally not sufficient to completely protect puppies against parvo virus.  Unfortunately, maternal antibody does effectively interfere with the puppy’s vaccines.  A puppy’s maternal antibody will usually wear off by the age of 12 weeks, but in some puppies it can last until they are 18 weeks old.  For this reason, a puppy’s vaccines are given every 3-4 weeks until they are at least 16 weeks old.  This generally ensures that the dog has received at least one dose of vaccine after his maternal antibody has worn off.  In higher risk breeds such as those mentioned above, vaccines may need to be continued to the age of 22 weeks in order to ensure that the dog receives at least one vaccine after his maternal antibody has waned.

The vaccine against parvo virus is highly effective when given according to your veterinarian’s recommendations.  It is always crucial that, if you have a dog under the age of two years, your dog’s vaccines against parvo virus are up to date.  Parvo rarely infects dogs over the age of six months, and I have not personally ever seen a case of parvo virus in a dog over the age of two years.

If you are unsure of your dog’s current vaccine status, please contact your veterinarian.  Dog owners who have updated that their pets’ vaccine status against this ubiquitous virus have no need to be alarmed during the spring and fall when parvo virus is at its most active.

A BIG THANK YOU to Dr. Jody for sharing this article.  🙂

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