 CURRENT THOUGHTS ON PARVOVIRUS INFECTIONS IN DOGS & CATS
Shawn Messonnier DVM
Each year, millions of dogs and cats receive immunizations for a number of infectious diseases. By far, one of the most important diseases for which pets are immunized is parvovirus infection. In this article, I’ll update you on these infections in dogs and cats, and present some new thoughts on immunization.
Parvo Viruses
In dogs, parvovirus was first recognized as a clinically important disease in the 1970’s. As I was enrolled in my pre-veterinary studies, I clearly remember seeing acute death in a number of puppies. At that time, there were two forms of the disease that were eventually traced to parvoviral infections. One was an acute death without any clinical signs. This form of the disease, which basically resulted from cardiac failure (a heart attack) and was 100% fatal, occurred in very young puppies, usually under 8 weeks of age. (This form of the disease is very rarely seen now.) The other form of the disease, which still occurs today, manifested as a disorder of severe gastroenteritis. Puppies older than 8 weeks of age began vomiting, and within 12-24 hours progressed to severe bloody diarrhea, dehydration, and shock. Many of these puppies died despite treatment. Now we know that the disease causes severe illness and death due to dehydration coupled with severe secondary infection (bacteria enter the body through the damaged intestines.) As a result, aggressive treatment with intravenous fluids, antibiotics, and other supportive therapy results in close to 100% successful treatment.
In cats, the parvovirus (panleukopenia) is a very rare disease, since most cats are immunized against this infection. When seen, clinical signs most commonly occur in young kittens and include lethargy, anorexia, vomiting, diarrhea, fever, and depressed white blood cell counts. If a pregnant cat is infected with the virus, the kittens exhibit shaking due to failure of the cerebellum (a part of the brain that controls coordinated movements) to properly develop.
Treatment
Treatment of parvoviral infections in dogs and cats is basically supportive, as there is no “magic drug” to cure the disease. Intravenous fluid support to counteract shock, prevent kidney failure, and dehydration is essential in treating parvoviral infections. This typically requires 24-hour hospitalization to administer the fluids and monitor response to therapy. Intravenous antibiotics are also given to kill secondary infections, which are typically the cause of death in pets with parvoviral infections. Non-steroidal medications may be used judiciously to reduce inflammation in the gastrointestinal tract. Medications to control nausea are needed to allow quick return to feeding. As the pet improves, oral fluids and feeding of a bland diet will allow return of normal gastrointestinal function. As I use an integrative approach in my practice, combining conventional and complementary therapies, I also use several supplements in my patients. Bentonite clay is given to adsorb GI toxins. Probiotics restore normal GI flora, replacing those normal bacteria and yeast destroyed by abnormal gut pathogens. Glutamine, an amino acid, has been shown to hasten healing of GI problems and serves as fuel for the intestinal cells. Ginger is well known as an anti-nausea agent. As a rule, most pets recover after 72-96 hours of intensive therapy.
Prevention and Changes in Vaccine Protocols
Since the fecal-oral route transmits parvovirus, it is essential to prevent exposure to infected fecal material. Keeping cats indoors, walking dogs on leashes and preventing access to stray feces, and deciding not to take in stray pets as foster pets is essential in preventing exposure.
Since infectious organisms for which vaccines have been developed cause parvo virus infections in dogs and cats, immunization is an important part of preventive strategy. Currently all vaccines for dogs and cats are licensed and labeled for annual use. There is no benefit in more frequent vaccination for adult dogs and cats. Due to concern about the possible side effects of repeated, unnecessary vaccines, including sarcoma cancer lesions in cats, vaccine protocols have recently been reviewed. Several studies by veterinarians, including Dr. Fred Scott and Dr. Jean Dodds, have revealed immunity lasting longer than 1 year in many pets vaccinated for parvoviral infections. In Dr. Scott’s study, he found that cats vaccinated against feline parvoviral infection (panleukopenia) had protective titers that persisted at least 5 years after immunization. Dr. Dodds has found that dogs vaccinated for parvo virus have protective titers lasting longer than 12 months. As a result, the American Veterinary Medical Association (AVMA) and the American Association of Feline Practitioners (AAFP) have made the following recommendation for parvoviral infections. After the initial puppy and kitten series of immunizations, vaccination for parvo virus should be done every 3 years.
The decision on how often to immunize ultimately rests with each individual veterinarian. While some doctors are changing their protocols to vaccinate for various diseases, including parvo virus, every 3 years, other veterinarians are sticking to the prior recommendation of annual immunization. Why the discrepancy? First, it’s hard to change tradition. Second, many doctors are old enough to remember the high mortality seen with diseases such as parvo virus that occurred prior to the discovery of effective vaccines. Others question the new research available showing the persistence of protective titers longer than 12 months. For examples, some doctors point to a study reported in the Journal of the AVMA (Vol. 213, July 1, 1998) that showed that 27% of dogs vaccinated less than 400 days previously tested for parvoviral titers had a less than protective titer. Additionally, some practitioners question the findings in Dr. Scott’s research since he only studied a small number of cats. As is often the case, it’s often a question of each side having “his research” to back up his position.
I recommend using a more holistic approach, which lets each pet’s body determine what it needs. In my practice, this means we draw blood each year for antibody titers to parvovirus, and only vaccinate healthy animals with low titers. This middle-of-the-road approach recognizes the differences in the findings of the various research protocols, and accepts the fact that each pet is an individual and should be treated as such. To date, most dogs maintain protective titers at least 2 years since the most recent immunization. Order the special report. "ARE VACCINES KILLING OUR PETS? NEW THOUGHTS ON VACCINATING YOUR PET", for a more in-depth look at using titers in place of annual vaccines to keep your dog or cat healthy.
Parvoviral infections in dogs and cats can be fatal diseases. Fortunately, early diagnosis and aggressive treatment now means that most pets can be saved and live normal lives. Reducing exposure to infectious viral particles and using a sensible vaccination protocol minimize the chances of infections. Ultimately, how often to immunize your pet will require a discussion between you and your doctor. In a future article, we’ll talk more about the use of vaccine titers to help determine just how often pets should be immunized.
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