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VACCINATIONS: WHAT PETS NEEDS THEM AND HOW DO THEY WORK?
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The basic principle of vaccination
was discovered by an English scientist, Edward Jenner, in 1796. He
saw that the girls who milked cows often got cowpox, and that seemed
to make them immune to a more serious disease, smallpox. From these
humble beginnings did develop the wide array of modern vaccinations
that are available to our pets today
The first step in making a vaccine
is to identify and isolate the disease's causative organism. Usually
a virus, it is then weakened or killed until it is safe to be given
to the susceptible individual. With a normally functioning immune
system, the body can then figure out how to produce protective
substances called antibodies which specifically attack and
neutralize the virus. When a booster vaccination is given at a
later date, the immune system is reminded that it has already been
exposed to this germ and is able to produce more antibody, more
rapidly and more efficiently.
When the real disease comes along
the immune system is ready and is capable of destroying the
challenging virus. This kind of immunity is called active immunity.
When puppies and kittens start
getting vaccinated at eight weeks of age, they usually receive a
series of vaccinations. Why is this necessary? It has to do with a
process called maternal interference. Unlike people, puppies and
kittens receive virtually no antibodies from their mothers while in
the uterus. They obtain all their antibodies from nursing during
the first twenty-four hours of life. After twenty four hours, the
intestine stops absorbing the antibodies and starts digesting them.
This is why it is critical for nursing to occur! The absorption of
the antibodies produces a passive immunity-- meaning that these
antibodies are on loan only, the body is not actively producing
them. Because of this, the passive immunity will last only a few
weeks. There is always a two week period between eight and sixteen
weeks, where the level of passive immunity is too high to allow the
vaccination to work but yet is too low to protect the individual
from the disease, even if we administered a vaccine every day!! For
this reason, it is recommended that while the puppy or kitten is
undergoing its initial series of vaccinations, it should not be
exposed to areas of public access. Stray dogs and cats are the main
reservoirs of dog and cat distemper as well as canine Parvo and
feline leukemia viruses. The worst places to take a new puppy or
kitten are the parks and beaches as well as on public streets. It
is ok to take them to a friend’s house or have their pets visit your
home as long as you know the health and vaccination status of these
pets.
Recently, there has been much
discussion in the veterinary community regarding how frequently
booster vaccinations should be given. When the original guidelines
were established thirty some years ago it was decided to advise
annual vaccinations. This philosophy catered to the lowest common
denominator theory. This school of thought felt that the frequency
of the boosters should be based on the animals that had the weakest
immune response to the vaccine- that is, if ten percent of those
vaccinated only maintained immunity for a year, then in lieu of
testing each dog for its antibody level, all individuals were
advised to get yearly vaccines. Now the philosophy seems to be
changing and many of us in the veterinary profession are expecting
to see revised vaccination schedules which call for boosters every
two to three years. The cost of testing for antibody levels has
decreased dramatically (although it is still three to four times as
expensive as the vaccine) and it is now feasible to run antibody
assays especially for those pets who have had previous adverse
vaccination reactions or whose immune system has been suppressed
through disease.
Consult your local veterinarian
for professional advice as to the type and frequency of vaccinations
that will benefit your pet.
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