One of the things I dreaded seeing most while practicing veterinary medicine was canine parvovirus. I used to always say, if every single person could visit a clinic and see an outbreak of parvo and how it affects puppies, they wouldn’t hesitate to get their animals vaccinated for this horrendous disease.
What is Canine Parvovirus?
Canine parvovirus is a highly contagious, potentially deadly virus that affects mostly puppies, young dogs, or unvaccinated adult dogs. It is a very hardy virus and is able to live for long times in the environment (over a year) and seems to be very resistant to extreme heat and extreme cold. It is also very resistant to many disinfectants. It first emerged in the late seventies (around 1978). Several breeds seem to be more susceptible to parvo. Among these breeds are: Doberman Pinschers, Rottweilers, American Pit Bull Terriers, Labrador Retrievers, English Springer Spaniels and German Shepherds. The majority of affected dogs are less than one year old and the most severely affected are pups under 3 months of age. The most common form of parvovirus is the intestinal form. There is a less common form which affects the heart in very young pups causing a myocarditis (inflammation of the heart) which is usually fatal. Thankfully, this form is rarely seen now. Canine parvovirus does not affect humans (and that’s a good thing as I would have been dead long ago). Household bleach kills the virus and is an inexpensive way to disinfect after an outbreak. A 1:32 dilution of bleach will kill parvovirus (or 4 oz. of bleach to a gallon of water).
How does a dog get parvo?
Parvo is spread through infected feces either directly or indirectly by fomites (shoes, toys, brushes, combs, feed bowls, bedding, clothing, etc.). The incubation period of parvo is about 5-7 days. This is the time from exposure to the time the dog starts showing symptoms. Dogs in kennels, pounds, and pet shops are most likely to get parvo (anywhere there is a large congregation of dogs).
The intestinal form is the most common form of parvo. Signs may be mild or severe. Signs seen are a severe lethargy and depression, vomiting, diarrhea, and dehydration. The diarrhea is often very bloody, may contain mucous and has a characteristic odor. Affected dogs are anorexic and usually will fun a fever. I will mention that some of the most depressed dogs I have ever seen are dogs affected with parvo. Parvo pups feel miserable. I will also mention that once you smell that characteristic parvo smell, you will never forget it.
A diagnosis is based on the clinical signs the animal is showing along with a confirmed positive parvo test. Most veterinary clinics have the ELISA test which is performed on the feces and takes about 15 minutes. A complete blood count (CBC) will often show a leukopenia (a decrease in white blood cells) which if severe, is usually a poor prognostic sign. Serum chemistry panels can help assess the electrolyte status of the animals (especially hypokalemia, or low potassium from the vomiting, and hypoglycemia or low blood glucose).
There is no specific treatment for parvovirus. Treatment is symptomatic and supportive. Prompt and aggressive treatment is vitally important and hospitalization is usually required. IV fluids with balanced electrolyte solutions are given to replace fluids lost through the vomiting and diarrhea. This is perhaps the most important part of treatment. Food and water are restricted while the animal is vomiting. Antiemetics are given to ease the nausea. Antibiotics are given for secondary bacterial infections. Dextrose is usually given in the IV fluids (to supply some calories and raise the blood glucose) along with B-complex and B-12 vitamins. Blood transfusions may sometimes be necessary. If the animal is in shock, corticosteroids may be administered. Good nursing care and lots of TLC are important.
It is very difficult to predict which animals will survive parvo and which will succumb to it. Personally, as a veterinarian, I quit trying to predict outcomes as I usually ended up very frustrated. I saw dogs that I would have sworn would die from their illness who went on to recover and other dogs with mild cases which were treated very aggressively that I thought had a pretty good chance of recovering, but who died. I recall seeing a litter of beagle pups in which every single pup in the litter got the disease. The first pup to contract the virus was the sickest (barely responsive with purple mucous membranes and frank blood pouring out its rectum when it presented to the clinic one night) and I was sure that pup would die. Aggressive treatment was started immediately, and that puppy survived. The remaining littermates presented the following day with much less severe symptoms and all died despite treatment. The moral of the story is: Parvo is very unpredictable!!! In general, most dogs that survive for the first 3-4 days of treatment will usually recover. Once the vomiting stops, a bland diet is started in very small amounts and fed several times a day. Contaminated areas should be disinfected with the bleach solution, disinfecting any surface and object that can be cleaned, such as floors,walls, cages, food bowls, toys, combs, shoes, hands, etc.
Vaccination is very important in the control of canine parvovirus. Talk to your veterinarian about his/her vaccination protocol and recommendations to protect your dog against this deadly virus. Unfortunately some vaccinated pups do get parvo. The most common reason for this is that maternal antibodies can cause a decrease in vaccine efficacy. Maternal antibodies are the antibodies present in the mother’s first milk or colostrum for the first 24 hours after the pup’s birth. These antibodies protect the puppy against disease and viruses. High levels of these antibodies will block the effectiveness of the vaccine. All puppies have a “window of susceptibility” of at least several days (maybe weeks) when they are at risk of contracting parvo. What happens is the maternal antibodies are at a low enough level that they do not afford protection against parvo, but they are at a high enough level that they can still block the effectiveness of the vaccine. The length of this window of susceptibility is different for every single puppy. Eventually the maternal antibodies will drop to a low enough level where a parvo vaccine will be effective. Once the complete puppy vaccination series for parvo is complete, a yearly vaccination is usually recommended.