WRANGLING ON THE RANGE #110
VACCINE WARS - THE BREAT DEBATE
Are you over or under vaccinating your horse? Hear both sides of
the debate surrounding vaccination to decide what's best in your
BY BARB CRABBE, DVM
Vaccination has been called "medicine's greatest triumph,"
responsible for nearly eradicating childhood killers such as
polio and smallpox. Vaccinating your horse protects him against
equally frightening diseases, including tetanus and sleeping
sickness, both of which are almost always fatal. In the past
decade, however, vaccine opponents have raised concerns about
vaccinations - and even begun to question whether they're
necessary at all.
Should you continue to vaccinate your horse? If so, which
vaccines should you give? It's hard to know what's right. In this
article, I'm going to investigate the top five arguments I've
heard made against vaccination - in both human and veterinary
medicine. While some of the concerns are legitimate, many more
are not - and consequences of undervaccination can be even more
frightening than the fears of vaccine opponents.
Once you've heard all sides, I'll give you a set of rational
questions to ask to make educated decisions about your own
horse's vaccination plan.
POINT #I: VACCINES ARE DANGEROUS. Overheard:
"They lead to a hyperstimulated immune system and all kinds of
health problems. I've read on the Internet that vaccination
causes headshaking and allergies in horses, too."
When it comes to horses, there are no legitimate studies that
link vaccination to diseases related to an over-stimulated immune
system such as allergies or skin disease. The stories you hear
are just that - stories. While there may be other reasons to
question whether or not to administer a certain vaccine to your
horse, this simply isn't one of them.
POINT #2: THE SIDE EFFECTS ARE AWFUL. Overheard:
"OK, so maybe there's no scientific proof that vaccination causes
other diseases, but the side effects from vaccines are horrible.
Every time my horse gets vaccinated he can't lift up his head for
days. Death is even possible."
Yes, vaccinations can cause side effects - some more than others.
And this is clearly a legitimate reason to consider your horse's
vaccination program carefully. Some horses are more sensitive to
vaccines than others, and if yours is one that seems to have a
problem every time he's vaccinated, you may choose to take the
minimal-vaccination route. In this situation, the concept of
"herd immunity" comes into play: If 80 percent of the population
in a herd is vaccinated, the remaining 20 percent have some
protection against a serious outbreak.
If your horse is a reactor, you should look at individual
vaccines carefully. Vaccines for some diseases are more
problematic than others, and different forms of vaccines for the
same diseases have different reactivity. Ask your vet to help you
decide which vaccines are most important due to exposure risk and
severity of disease.
Once you've decided which diseases are most important to target,
look at the different forms of each vaccine available. For
example, killed-virus vaccines may not be quite as effective as
modified-live-virus vaccines, yet they typically cause much less
significant reactions. And intranasal vaccines for respiratory
diseases are often much less reactive than their intramuscular
If you're considering strangles vaccination (a vaccine with high
risk for side effects), you can measure antibody levels in the
blood prior to vaccinating; if antibody levels are high, your
horse is at greater risk for serious side effects (and could be
protected anyway), so don't vaccinate.
Finally, if your horse is exceptionally sensitive, ask your vet
whether it would be advisable to administer a dose of a
non-steroidal anti-inflammatory medication such as flunixin
meglumine (Banamine«) prior to vaccination to minimize side
As an example, we have a horse in our practice that's highly
reactive to vaccines. He spikes a fever, his legs swell, and he
can even act a little colicky afterwards. He lives in a big, busy
competition barn, where his exposure risk is high. His
vaccination program consists of tetanus - because it's such a
safe vaccine against an extremely dangerous diseaseand influenza
given intranasally, where side effects are extremely rare. He's
lucky to live in a barn where the other horses are on a solid
vaccination program so herd immunity is high. And he receives a
dose of Banamine prior to every tetanus vaccine to minimize his
risk of side effects.
POINT #3: VACCINES ARE UNNECESSARY. Overheard:
"I've never known a horse to get any of the diseases we vaccinate
Guess what? I have. And if you've ever seen a horse with tetanus,
I can promise you won't ever want to see it again.
One of the factors contributing to the current trend against
vaccination is a bit ironic. We live in the vaccination age. Many
of us have never seen these diseases - because they've been held
in check so effectively by vaccination.... horse owners have been
saved from the heartache of watching their horse die of tetanus
following a simple wound. Yet if you look around, there are
countless examples where serious outbreaks have occurred that
could've been prevented by vaccination.
Most recently, Eastern equine encephalitis, a form of sleeping
sickness, has been on the rise in the United States. Outbreaks
have been reported during the past two years in many states,
including Florida, Michigan, New York, Maine, Georgia, Louisiana,
Connecticut, New Hampshire, and Massachusetts. This
mosquito-borne disease is almost always fatal, can spread to
humans, and is completely preventable by vaccination. According
to the Center for Disease Control, nine human deaths from EEE
have been reported during the past six years. Most of the
reported equine cases in recent outbreaks have been in
In 2007, Australia experienced a devastating influenza outbreak.
Large numbers of horses became ill or died, and the entire equine
industry was shut down for many months. Why was this outbreak so
severe? Australia had previously been influenza-free - with the
result that horses had no natural immunity and were unvaccinated
when they became exposed. Had they been vaccinated, this outbreak
would've been much more easily controlled, and many lives
would've been spared.
West Nile virus is another interesting case. When this disease
first hit the East Coast in 1999, many horses became ill or died.
By 2001, a vaccine was developed, and widespread vaccination of
horses across the country occurred. As the disease spread west,
the incidence and severity declined significantly. The reason?
Vaccination clearly played a role. As horses were vaccinated,
they became less likely to contract the disease both limiting its
spread and helping to minimize the severity of disease for horses
that did become ill.
The lesson here is that we can't become complacent. Just because
we don't see the diseases at the barn next door doesn't mean they
no longer exist.
POINT #4: VACCINES ARE EXPENSIVE. Overheard:
"You can save hundreds of dollars if you just skip them."
This is faulty logic. The cost of vaccination pales in comparison
to the cost of treating a serious disease. For example, an annual
tetanus vaccine costs between $10 and $15 (it might even have
sleeping sickness included in that price). To provide supportive
care for a horse affected with tetanus would run in the
thousands. And what if your horse doesn't make it?
Costs associated with less deadly diseases add up, too. Consider
an outbreak of a simple respiratory virus in a barn. Although it
may not be terribly expensive to treat each individual horse, it
can mean weeks or even months of lost training time and missed
POINT #5: VACCINES DON'T WORK. Overheard:
"I've heard of vaccinated horses still getting the disease in
question, so vaccinations aren't really effective."
Simply not true. Although vaccinations won't completely prevent
every instance of disease, they do make a difference. Some, like
tetanus and sleeping sickness, are extremely effective for
preventing clinical illness. Less effective vaccines can still
help keep symptoms to a minimum if your horse does get sick. And
most play a big role in preventing outbreaks by helping to
So while you can't expect vaccination to be 100-percent
protective, you should recognize the importance of a vaccination
program for keeping your horse healthy.
So, should you vaccinate your horse with every vaccine available,
or not at all? Just as with most great debates, the answer to the
vaccine question rests somewhere in the middle. Most importantly,
you should evaluate risk vs. benefit to your horse for every
individual vaccine. In other words, is the risk of the vaccine
greater than the risk of the disease? If so, just say no. If not,
When deciding whether or not to vaccinate, it's especially
important that you get your information from a reliable
source. Your veterinarian is likely to know more about the
different vaccines available than anyone - and is certainly more
reliable than the Internet or your barn buddies. If you're a
scientific type and need to see solid proof of efficacy or safety
studies, your vet can provide you with those answers in addition
to his or her personal opinion.
To help you decide on a rational vaccination program for your own
horse, ask the following questions about each vaccine you are
* How bad is the disease? Is it almost always fatal, or likely to
spread to humans, such a tetanus or FEE? If so, vaccinate if you
can. For diseases that are usually mild or easily treatable, such
as strangles, vaccination may not be as important.
* What is your horse's exposure risk? Does your horse live in a
pasture by himself with no exposure to other horses? If so,
rabies vaccination might be more important than influenza due to
his potential exposure to wild animals that carry the rabies
virus. Does he live in a stall in a busy competition barn? He's
less likely to contract rabies, but vaccinating against influenza
would be advised.
Where you live and your horse's lifestyle play big roles in
determining his risk for specific diseases. Ask your veterinarian
* How effective is the vaccine? There's no doubt about it: Some
vaccines are more effective than others. And a vaccine that's
more effective is more worth giving. Vaccines for tetanus,
Eastern/Western encephalitis, and rabies are all known to be
highly effective (and with minimal side effects - see below). In
most situations, it just makes sense to vaccinate.
On the opposite end of the spectrum is equine herpes virus
(rhinopneumonitis). Although the vaccine for this disease may
help minimize signs, it's unlikely to prevent illness completely,
and has no efficacy at all against the most severe, neurologic
form of the disease. It may not make sense to administer this
vaccine unless exposure risk is very high.
* What type of side effects can you expect? Some vaccines carry
much greater risk of side effects than others. If a vaccine is
known to cause more reactions, and/or if your individual horse
seems particularly sensitive to it, that could be one to skip -
particularly if the disease is a less serious one and/or your
horse's risk of exposure is low.
The take-home message? By asking the right questions, you can
protect your horse against devastating disease with minimal risk
through a carefully designed vaccination plan.
FEBRUARY 2011 HORSE&RIDER
To be continued from time to time