by Christie Keith

"Don’t put your dogma before your dog" is Christie Keith’s guiding philosophy. She provides a thoughtful and balanced look at conventional and holistic health practices, so you can make informed choices.

For the last 20 years, I’ve raised my dogs holistically, feeding them a home-prepared diet, giving them plenty of fresh air, sunshine and love, minimizing the risks in their environment and working with holistic veterinarians. During this period two subjects have been without question the most controversial: raw diets and vaccination. Th is month’s column will be the first of a two-part look at canine vaccination from an integrative viewpoint.

Few areas of veterinary medicine and responsible pet ownership have undergone as much debate in the last few years as vaccination. Which vaccines are essential? How oft en should vaccines be administered? How long does immunity from vaccines last? Is it possible to minimize or even eliminate vaccination and still protect our dogs from infectious disease?

Most people would like nothing more than one fi nal and irrefutable answer to all questions regarding vaccination for our pets, but that answer doesn’t exist and likely never will. Despite an increasing understanding of the immune system, the development of new vaccines for pets, and the growing popularity of alternative vaccine protocols, we are oft en left with as many questions as answers when we begin investigating canine and feline vaccines.

On the other hand, not everything is unknown. From the research of veterinary immunologists and biologists a picture emerges that is far less blurry than before.

In the last issue of FETCH, Dr. Christopher Forsythe presented an overview of canine and feline vaccines. He introduced the idea of core and non-core vaccines, and discussed alternative re-vaccination protocols. All of those ideas are from the cutting edge of veterinary medicine, and can seem radical to pet owners who have been following older suggestions to vaccinate all pets for all diseases every year. Even these seemingly radical new approaches, however, are mild compared to the path research has us on today.

How long do vaccines last?

The "gold standard" of vaccine research, the challenge test, and epidemiology tell us pretty clearly that established immunity to canine parvovirus and canine distemper are very long lasting. Parvo especially is almost always a disease of puppyhood when, due to maternal antibody interference, vaccination does not always result in immunity. We know that once immunity has been established it lasts at least seven years and probably the life of the dog (Canine Infectious Diseases: From Clinics to Molecular Pathogenesis, 1999; "Duration of immunity to canine vaccines: What we know and don’t know;" R. D. Schultz, PhD, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA). We know that you cannot make an immune animal "more immune" to a virus by giving a "booster shot"; the pre-existing immunity will wipe out the vaccine virus and produce no increase in protection for the animal. (Donald J. Klingborg, DVM, Council on Biologic and Th erapeutic Agents of the American Veterinary Medical Association, 2000 AVMA Convention, Salt Lake City, UT).

However, just as you can get strep throat, a bacterial disease, over and over again, but can get measles, a viral disease, only once, your dog’s immunity to bacterial diseases will wane over time and can be "boosted."

On the other hand, just because an animal was previously vaccinated does not mean she is immune. Vaccination does not necessarily equate to immunity: improper handling, storage, or administration of a vaccine can result in immunization failure. Fortunately, you can use a titer test 10-14 days aft er vaccination to determine if immunization has occurred (more discussion of titer testing will follow next month).

Canine viral vaccines

The four canine diseases, usually considered "core," that can be vaccinated against are rabies, canine parvovirus, canine distemper, and canine infectious hepatitis.

There is no question that canine parvovirus is both common and deadly. Few dogs can avoid being exposed to it. It causes violent gastrointestinal disease in dogs; in very young puppies it also damages the heart. The modified live virus vaccine for canine parvovirus is one of the most effective for any disease in any species, and there is no evidence that immunity, once established, will ever wane or vanish (Recent Advances in Canine Infectious Diseases, "Considerations in Designing Effective and Safe Vaccination Programs for Dogs," R. D. Schultz, 2000).

Canine distemper is much more rare than "parvo" in pet dogs, but still prevalent in shelters and other environments where dogs are crowded and stressed. Since most of these dogs come into the pet population, an outbreak among pet dogs is always possible. Furthermore, some species of wildlife carry canine distemper.

Fortunately, the canine distemper modified live virus vaccine is also extraordinarily effective, and as in the case of vaccination for parvo, there is no evidence that immunity, once it has formed in response to vaccination, diminishes over time (Schultz, 2000).

While considered a "core" vaccine, canine infectious hepatitis is a very rare disease, and many veterinarians have never seen a case. However, the vaccine off ers cross-protection against a related virus that causes respiratory symptoms in dogs, so it continues to be recommended for all dogs.

A California-approved three-year rabies vaccination must by law be administered to all dogs by a licensed veterinarian once, then again within one year, than every three years after that. Dogs with health issues preventing safe vaccination for rabies can usually obtain a waiver from their veterinarian. Although rabies vaccine is made from killed virus, it is still extremely effective. The Centers for Disease Control (CDC) reported that in "a nationwide study of rabies among dogs and cats in 1988, only one dog and two cats that were vaccinated contracted rabies. All three of these animals had received only single doses of vaccine; no documented vaccine failures occurred among dogs or cats that had received two vaccinations." ("Recommendations of the Immunization Practices Advisory Committee," March 22, 1991, United States Centers for Disease Control.)

Another viral vaccine available for dogs is canine coronavirus. According to Dr. Ron Schultz, a leading canine vaccine researcher and head of the Department of Pathobiology at the University of Wisconsin School of Veterinary Medicine, "Although approximately 50% of practices routinely use coronavirus vaccine, most vaccine experts agree that this vaccine is not needed. Some experts consider CCV vaccines useless. Clinical disease rarely occurs with CCV infection and when disease does occur it is usually mild, self-limiting and most commonly seen in pups less than 8 weeks of age - an age which is earlier than vaccine would provide benefit." (Schultz, 2000). In an interview in DVM Newsmagazine, vaccine researcher Dr. Richard Ford said, "We’re not recommending it because the disease isn’t significant. The vaccine is safe, there just isn’t a disease to go with it."

Canine bacterial diseases

Bordetella bronchiseptica causes respiratory symptoms in dogs, similar to those of a human cold. Along with the two viruses mentioned above and other bacteria and viruses for which we have no vaccines, it is part of what is known as the "kennel cough" complex, which includes several forms of infectious respiratory infections in dogs.

Bordetella vaccination is usually recommended for dogs who are likely to be exposed to it, and re-vaccination is advised at frequent intervals if exposure is ongoing. This is not considered a core vaccine, however, as the disease is, in most dogs, not serious.

Canine leptospirosis is a highly infectious disease that is transmissible to humans. It is spread by rodent urine. It causes kidney and sometimes liver failure, and left untreated will almost always be fatal. Some dogs survive only after costly kidney dialysis.

Despite the seriousness of the disease, "lepto" is not considered a core vaccine for a number of reasons. The vaccine causes more adverse reactions than any other canine vaccines. Even when effective in preventing illness,it does not prevent the carrier state of the disease. Since immunity is only temporary, repeated vaccinations are required, increasing the likelihood of an adverse reaction.

More critically, there are many strains of lepto, known as "serovars," but there is no cross-protection among lepto serovars. A dog can be immune to one serovar of lepto and have no protection at all from another. There are only four available vaccines for serovars of leptospirosis: L. Canicola, L. Gripophytosa, L. Icterohemorrhagiae, and L.Pomona. There are two more serovars that can cause disease in dogs, L. Autumnalis and L. Bratislava. We have no vaccines for these.

Since there is no cross-protection among serovars, and immunity is temporary, you always have to assume that a dog, vaccinated or not, might have lepto, particularly if symptoms are present. Therefore, I don’t think that routinely vaccinating a dog for those four serovars of lepto annually or even more often makes a great deal of sense for most dogs. However, if there is a known outbreak, you know the serovar, and there’s a vaccine for it, you may want to consider it. Lepto does infect humans, so it’s often a reportable disease. The local public health department might be able to tell you if there is an outbreak. Beyond that, word of mouth among localdog owners and information obtained at your vet’s office is the best early-warning system.

Borrelia burgdorferi, Lyme disease, has more complicated immune effects and deserves special consideration in terms of prevention, diagnosis, and treatment. (See sidebar.)