|
Conventional veterinary wisdom states that annual
vaccinations have decimated the incidence of formerly common viral
diseases such as feline panleukopenia, rhinotracheitis, feline leukemia,
canine distemper, hepatitis, and canine parvovirus. Vaccinations have
certainly worked to decrease the incidence of acute viral disease, but
many pet owners and some veterinarians have begun to question both the
need for annual, life-long re-vaccination, as well as the long term
consequences of vaccination in general.
 Although
Dr Jean Dodds suggested, as early as 1983, that autoimmune disease was
occurring in certain susceptible individuals as a result of
over-vaccination, concurring literature began to appear only in 1992.
Phillips and Schultz, of the Scripps Research Institute and University
of Wisconsin, respectively, reviewed the state of canine and feline
vaccine technology in Current Veterinary Therapy XI. One conclusion was
that annual vaccination was a widespread practice with no scientific
basis or verification. The immune response to most bacteria and viruses
lasts years, and the only exception to this rule is immunity to
bacterial toxins, such as tetanus toxin (necessitating yearly boosters
for horses, for example).
Dr
Schultz has further speculated that for most dogs, revaccination is
probably only necessary every three years, although the persistence of
immune competence may vary, since modified live virus vaccines stimulate
a stronger response from the animal than do killed vaccines. Dr Jim
Richards, of the Cornell Feline Health Center, has written that duration
of immunity in cats is also not well understood, despite the fact that
the need for annual revaccination is questionable.
Most
recently, an article appeared in the Journal of the American Veterinary
Medical Association entitled "Are We Vaccinating Too Much?"
The veterinarians interviewed included Dr Schultz, Dr Dennis Macy of
Colorado State University, Dr Leland Carmichael, and Dr Fred Scott of
Cornell University. These leading veterinary immunologists admit
puzzlement at the current situation but stop short of making
recommendations, since no studies have been done to show maximum
duration of immunity. When asked directly what should be done, Dr Macy
recommends continuing to follow vaccine label instructions, but to
pressure the USDA to determine the optimal vaccination schedule. The
other experts interviewed did not make specific recommendations but
emphasized the need for veterinarians to rationally analyze the
individual situation and vaccinate accordingly. In general, they felt
that cats should be immunized every three years for both FVRCP and
rabies, not annually.
Alternatives to Vaccination
Please keep in mind that this section discusses alternatives to
all vaccinations except rabies. Rabies vaccination is required by law in
most states. Rabies can be an urban disease, frequently found in
raccoons and foxes that raid suburban trashcans, and if your
unvaccinated pet is exposed, the disease is invariably fatal. The
majority of rabies
cases in domesticated animals occur in
cats.
One
argument against vaccination has been that if we keep our animals
perfectly healthy, feed raw diets, good water, and give them a perfect
lifestyle, they will never succumb to these diseases when exposed. Many
students of environmental medicine believe that this perfect lifestyle
is simply impossible to achieve. There is not much that can be done
about the air we breathe, although indoor cats that live with the luxury
of multiple air filters may have an advantage here. It is well
recognized that city water systems are far from "clean," as
recent reports seem to suggest. Animals drinking distilled water may be
given a head start here. What about indoor air pollution? A recent
review detailed the potential sources of indoor air pollution to which
we are all subject, emphasizing that pets experience "comparable,
if not greater" exposure to these pollutants, which may include
nitrogen dioxide from gas appliances and water heaters, formaldehyde
from foam insulation, and household cleaning agents. Of course, outdoor
pets walk all over beautiful lawns full of chemicals, then walk into
their homes to lick their feet.
Add
to all of these insults the fact that purebred (and even mixed breed)
animals may have genetic tendencies that can lead to greater
susceptibility to these diseases and the potential for developing long
term side effects from these diseases or the vaccines designed to
prevent them. Because it is my belief that we cannot provide our pets
with perfectly healthy environments and bodies (or even determine
whether that is possible), it should be clear that we need to increase
the odds in favor of our pets.
Nosodes
may be one way to protect them; unfortunately, there is no convincing
evidence that nosodes do prevent disease. A few studies published in
homeopathic journals suggest that nosodes may decrease the severity of
active disease and possibly prevent the spread of epidemics, but these
studies are not well controlled. The results of one recent well
controlled study suggest that parvovirus nosodes are completely
ineffective in preventing parvoviral disease under experimental
challenge conditions. Until well designed studies are completed and
thousands of pet owners make a concerted effort to help with potential
retrospective studies, nosodes remain an unknown quantity, and I do not
recommend using them as a sole strategy for disease prevention.
I
recommend that puppies and kittens undergo an initial vaccination series
and that annual vaccination be continued for a year or two, depending on
the individual. Unfortunately, many dogs and cats begin developing signs
of allergy or other disorders early in life. It is not recommended that
sick animals be vaccinated, and chronic illness may include the gamut of
every day conditions like atopic skin disease, inflammatory bowel
disease, or spondylosis. If we don't want to risk vaccination, and we
don't know whether nosodes work, what next?
One
strategy being used by many veterinarians is to test antibody levels in
the blood of our pets. Antibody levels may suggest (but not conclusively
prove) how much immunity that pet carries against a specific disease.
For many diseases, antibodies are the prime source of protection against
disease, and a high level suggests that the animal may adequately
respond to the agent causing that disease. Conversely, low levels
indicate that the pet may be susceptible to contracting the disease in
question. These antibody tests are not perfect indicators of immunity,
and most immunologists suggest that we do not place total reliance on
them. They are, however, the best tests we have, and can give the pet
owner a rationale for not submitting a pet to vaccination, should there
be any argument.
Currently,
there are three laboratories in the country which test for these
antibodies, but more are coming on board with time. Some labs will set a
threshold for protection, although others will only give the
veterinarian a number, which must be interpreted in the light of
experience. The serologic tests of interest are IgG titers for feline
panleukopenia, feline herpesvirus, calicivirus, and feline syncytial
virus. Feline coronavirus titers are measurable, but interpretation is
difficult, so most veterinarians only use this test if clinical FIP is
suspected in a sick cat. Dogs can be tested for parvovirus, coronavirus,
herpesvirus, adenovirus, and distemper antibodies. Cats are not tested
for feline leukemia virus and immune deficiency virus by antibody
levels, but by the presence of the virus. Rabies antibody level tests
are not offered or recommended in animals due to the public health
implications (although human rabies titers are sometimes measured).
Practically
speaking, dogs should have antibody titers against canine distemper and
canine parvovirus evaluated. Canine hepatitis has been called an exotic
disease, and since it is rarely seen today, titer assessment is probably
unecessary. The need for other titers, such as leptospirosis, should be
evaluated according to the individual's general health and environment.
Cats should have titers to feline panleukopenia, herpesvirus, and
calicivirus tested. Be sure to advise the lab specifically of your
interest in antibodies to vaccination. The lab should, in this case,
change the normal testing technique by starting at lower serum dilutions
to give a more accurate answer.
Once
a number has been provided, how is this information interpreted? If the
levels are in the "protective range" (understand that this is
still a fuzzy number, due to the novelty of this technique in clinical
practice), you can assume that certain indicators suggest that the pet
has made an adequate immune response to those diseases. As wishy-washy
as this statement may sound, this information is a much better indicator
that the pet is protected than the simple act of vaccinating. Since not
all animals are genetically identical or live in identical environments,
scientists have no idea how each and every pet is going to respond to
vaccination. Is the pet going to be protected by vaccination? No way to
know for sure except to do antibody titers. If the titers already look
adequate, why vaccinate?
For
people who board their pets in facilities which require annual
vaccinations, protective antibody levels actually provide more precise
information about a pet's immune status than a simple history of
receiving vaccinations. Animals receiving nosodes may or may not develop
antibody titers, for reasons that would require pages more to explain.
Suffice it to say that a nosode protected animal with sufficient
antibody titers should still be considered adequately immunocompetent by
facilities asking for this information, and for those animals receiving
nosodes that do not develop titers, this rather inconvenient situation
remains the same--one cannot prove anything.
Antibody
titers are not going to save the pet owner any money, and they should
still be done annually, until we know how long these antibodies actually
last in the blood. These annual tests will give us peace of mind, while
at the same time helping to establish just how long vaccinations
actually protect the average dog or cat. Knowledge of how to more safely
and judiciously vaccinate our pets will save many thousands of pets
unnecessary iatrogenic illnesses.
Bibliography
W J Dodds (1983). Immune Mediated Diseases of the Blood. Advances in
Veterinary Science and Comparative Medicine 27:163-196.
T Phillips and R Schultz (1992). Canine and Feline Vaccines, in Current
Veterinary Therapy XI, W B Saunders, Philadelphia, PA
R Ford, et al (1995). Vaccines: Pioneering New Paths to Healthcare.
Emerging Science and Technology: Advances in Veterinary Medicine,
Fairway, KS
C Smith (1995). Are We Vaccinating Too Much? JAVMA 207(4): 421-425
J Dye and D Costa (1995). A Brief Guide to Indoor Air Pollutants and
Relevance to Small Animals. Current Veterinary Therapy XII, W B
Saunders, Philadelphia, PA
|
