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Vaccination:
Part I
Which ones do they
REALLY NEED, and HOW OFTEN?
by
Ann Brightman
A 3 part article published in Animal
Wellness Magazine
Volume 7 Issue 2. Publishing date:
March 15, 2005 |
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When
Helena took her new Sheltie puppy,
Mick, to the vet for his first check-up,
she felt more than a little anxious
when it came time for him to receive
his shots. While she wanted to protect
her new friend from deadly diseases
like distemper and parvo, she was
also concerned about the health risks
associated with over-vaccination.
Although Helena went ahead with the
vaccines and follow-up boosters, she
was worried about subjecting Mick
to subsequent annual shots, even though
her vet told her she was risking her
dog’s health even more by not
doing so.
 It’s
a common quandary these days, especially
as we hear more and more about the
often devastating side effects of
over-vaccination. How do we prevent
our dogs or cats from contracting
infectious diseases that can often
be fatal, while also protecting them
from the equally serious health consequences
of too many shots? The best strategy
is to learn which vaccines are absolutely
necessary (referred to as core vaccines),
why they’re needed, and what
the minimum requirements are for each
to ensure protection from disease
without over-vaccinating.
WHAT ARE CORE VACCINES?
“Core vaccines are those that
every dog or cat should receive, regardless
of geographic location or lifestyle,”
says Dr. Ron Schultz, Professor and
Chair of the Department of Pathological
Studies at the University of Wisconsin-Madison’s
School of Veterinary Medicine. For
dogs, the four core vaccines are canine
distemper (CDV), canine parvovirus-2
(CPV-2), canine adenovirus-2 (CAV-2)
and rabies. Those for cats are feline
panleukopenia or parvovirus (FPV),
feline herpesvirus-1 (FHV-1), also
referred to as feline viral rhinotracheitis,
feline calicivirus (FCV) and rabies.
In this article, the first in a three-part
series, we’ll be taking a close-up
look at canine distemper, feline panleukopenia
and rabies.
The eight vaccinations listed above
are considered core because the diseases
they protect against are distributed
over a wide area and have a high mortality
rate. “These vaccinations are
absolutely necessary,” says
Dr. Schultz. “You want the vaccine
to be the first antigens to prime
the immune system. You don’t
want to leave it up to natural immunization
or exposure.” This is because,
when compared to the actual disease-causing
virus, the vaccine is a safer way
to protect the animal. “If the
vaccine is live, it’s attenuated.
If it’s killed, it can’t
cause disease,” explains Dr.
Schultz. “It’s true that
many puppies that never see a vet
get naturally immunized by exposure
to distemper, as an example, but for
every one that gets vaccinated, probably
another would have died if the first
encounter with distemper occurred
prior to vaccination.”
MINIMIZING VACCINATION
Although core vaccines are necessary
to protect your companion from infectious
disease, even these do not need to
be given on an annual basis. “That’s
what we’re trying to change,”
says Dr. Schultz. “What we recommend
is that both puppies and kittens get
the core vaccines at least once at
or over the age of 12 weeks.”
The 12 weeks is significant, because
prior to that, many animals still
have passive maternal antibodies that
block immunization, which means they
may not respond to the vaccine and
are therefore unprotected against
the disease. American Association
Hospital Association (AAHA) guidelines
recommend vaccinating again at one
year, and once every three years after
that, although even that may not be
necessary. “I have studies that
show duration of immunity at seven
to nine years for all the core vaccines
except rabies, and even on an antibody
basis I can show that rabies gives
much longer protection than three
years,” says Dr. Schultz.
CANINE DISTEMPER (CDV)
CDV is a highly infectious and often
fatal disease that attacks the respiratory,
gastrointestinal and central nervous
systems. Although dogs of any age
can contract distemper, puppies up
to six months of age are most susceptible
to the disease, which
can cause a range of symptoms from
fever, loss of appetite and eye inflammation
in its early stages, to diarrhea,
vomiting, pneumonia, and neurological
complications such as ataxia, seizures
and paralysis.
Canine distemper occurs around the
world not only among domesticated
dogs, but also in many wild carnivores
such as raccoons, skunks and foxes.
“Wildlife is actually now more
of a reservoir for distemper than
dogs are,” says Dr. Schultz.
“The virus is spread mainly
by air, or by direct contact with
secretions from the infected animal.
The mortality rate among puppies with
distemper is 50% or higher.”
On the plus side, the distemper virus
is very fragile and easily destroyed
by outside influences. “It doesn’t
live very long in the environment,”
says Dr. Schultz. “It dies very
quickly because it is what we call
an enveloped virus. These kinds of
viruses are highly susceptible to
water, disinfectant and sunlight.”
Although there is only one distemper
serotype, there are several genotypes.
“What this means is that, from
an immunologic standpoint, it doesn’t
matter which distemper infects the
animal, they’re all similar;
the vaccine for canine distemper can
protect against the different genotypes.”
Dr. Schultz adds that modified live
vaccines (MLV) are most effective
for distemper. “In fact there’s
no question in my mind that you should
be using live vaccines for most of
the cores. Although attenuated, live
vaccines infect and replicate, and
that’s how you get immunity.”
Although AAHA recommends vaccinating
against distemper every three years
after the initial puppy shots, challenge
studies have shown that the minimum
duration of immunity can last five
to seven years, and perhaps even longer.
In fact, titers have indicated that
dogs can be protected for nine to
15 years. “To be honest, although
canine distemper is a core vaccine,
I think a dog only needs to receive
it once in his life,” says Dr.
Schultz. “The same goes for
canine parvo and adenovirus-2. That’s
the vaccination program I’ve
been practicing on my own dogs without
any difficulty whatsoever. We’ve
never had a vaccine-preventable disease
occur.”
Titer testing is highly effective
for canine distemper, but according
to Dr. Schultz, the best time to do
it is at two weeks or more after the
last puppy vaccination, to ensure
that the animal responded to its initial
vaccines. “To my mind, that’s
the only time it’s of medical
benefit to use a titer test for canine
distemper. After that, you don’t
really need to titer the animal since
you can easily go five or seven years
before the next vaccine.”
FELINE PANLEUKOPENIA (FPV)
Although FPV is sometimes referred
to as feline distemper, this terminology
is misleading. “When I talk
about feline ‘distemper,’
I always talk about it as feline parvo
or panleukopenia,” explains
Dr. Schultz. “The virus that
causes this disease is essentially
identical to the canine parvo virus,
but not the canine distemper virus.
If a dog has parvo, it can infect
a cat, but this doesn’t happen
with distemper.”
Most often found in kittens, FPV is
a contagious and deadly disease that
attacks and destroys growing cells
in the intestine, blood and nervous
system. It causes diarrhea, vomiting,
a lowered white blood cell count,
and neurological symptoms such as
tremors. Kittens up to six months
of age can easily die from the disease,
while older cats may develop much
milder signs. “There’s
a tremendous age-related resistance
to parvo,” says Dr. Schultz.
“If the animal is less than
a year old, mortality is 80% to 100%.
However, I rarely see mortality in
animals over a year of age, although
I might see mild morbidity. Nevertheless,
feline parvo is the one cat vaccin4e
I absolutely insist on.”
Like canine distemper, feline parvo
has worldwide distribution with outbreaks
occurring most commonly in urban areas
during the summer months. The disease
is transmitted by direct contact,
although cats can also contract FPV
from the fecal matter of an infected
feline. Unlike canine distemper, the
parvo virus is extremely long-lived,
and can remain active in the environment
for months or even longer. “Parvo
is what we call a naked virus and
is one of the most resistant,”
says Dr. Schultz. Soil contaminated
with the parvo virus still has the
ability to infect an animal a year
later. “In fact, parvo is more
often caused by environmental contamination
than direct contact with an infected
animal. You don’t need the infected
cat to be in the environment for very
long in order for it to leave the
virus behind.”
As with canine distemper, MLV vaccines
are very effective for preventing
feline panleukopenia. “With
parvo, in fact, you’d better
be using live vaccines, because the
killeds don’t work.” As
with other core vaccines, kittens
should be vaccinated at 12 weeks.
Titer testing is very effective for
this disease, although challenge studies
indicate that a vaccinated kitten
can remain protected from feline parvo
for eight years.
RABIES (RV)
Unlike distemper and parvo, rabies
is a disease that can be transmitted
from animals to humans, which is why
rabies vaccinations are required by
law throughout North America. The
virus infects the central nervous
system, causing encephalitis and death.
Symptoms can include confusion, partial
paralysis, aggressive behavior, excessive
salivation and other neurological
signs. Although rabies occurs worldwide,
including in Asia, Africa and Latin
America, some countries such as the
U.K. are rabies-free. In North America,
rabies is most prevalent in the eastern
portions of the continent, although
cases can occur anywhere. Wild animals
such as raccoons, skunks, bats and
foxes are the major carriers. Because
rabies isn’t age-related, mammals
at all stages of life can be affected
with the same degree of severity.
The chief means of transmission is
by a bite from an infected animal.
“There are multiple strains
of rabies, but the important thing
is that the vaccine prevents infection
with all those different strains,”
says Dr. Schultz. “Although
the risk of infection in domesticated
animals is generally low, the public
health concern is the issue. That’s
what drives the regulations for rabies
vaccines.” As with the other
core vaccines, puppies and kittens
should be vaccinated at 12 weeks.
Although some states and provinces
have approved a three-year rabies
vaccine, some still require annual
re-vaccination for dogs and cats,
even though the duration of immunity
based on challenge studies has been
shown to be three to seven years.
“The regulations vary from state
to state and province to province,
and even from municipality to municipality.”
It’s also important to realize
that a municipality might have a more
restrictive requirement than the state
or province it’s a part of,
although not the other way around.
“Rabies titers are effective,
but there’s no point running
them because you’re going to
have to vaccinate your animal by law
anyhow,” says Dr. Schultz. However,
titer testing for rabies is useful
in cases where the animal has had
an adverse reaction to the vaccine,
or has a medical condition that could
be aggravated by the vaccination.
“In these situations, local
municipalities will sometimes accept
a letter from the vet as a reason
not to vaccinate every three years,
But the guardian has to understand
that the animal is still considered
to be non-vaccinated, and if it bit
someone, it would be treated as such
if it’s gone beyond the three
years, irrespective of the vet’s
letter. Even so, if you have a dog
that for health reasons
shouldn’t be given a rabies
vaccine, it’s better to take
the chance of it being quarantined
for biting someone than to give the
vaccine and kill the dog.”
BACK TO BASICS
Vaccinations definitely have their
place in disease prevention, but knowing
where to draw the line is key. “I’ve
seen it go from no vaccines back in
the mid-1960s, to where we just kept
adding one after the other,”
says Dr. Schultz. The pendulum has
since started swinging back again
as organizations such as AAHA and
American Association of Feline Practitioners
(AAFP) began looking more closely
at which vaccines out of the 12 for
cats and 16 for dogs were really needed
and why. “We used to have one
manufacturer that made a canine vaccine
combo with 13 different components
in it. That’s not good, and
that’s why it’s not available
anymore.” Now, by contrast,
companies are coming out with information
demonstrating that their products
give duration of immunity lasting
several years. “All the major
manufacturers are coming on board
and saying that their core vaccines
give at least three years immunity.
To me, that’s the greatest gratification
in the more than 25 years I’ve
been doing this.” |
| Continue
- Read Part II (Volume
7 Issue 3) |
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