What are you doing when you vaccinate your horse? When we
vaccinate our horses we are deliberately exposing them to
a portion of a disease-causing organism or exposure to a disease
causing-organism, such as the bacteria or virus of a disease.
This is done in a very small dose. We do this in order to
cause an immune response in the horse that will hopefully
protect the horse in the future from that particular disease.
Generally, this is how vaccines work.
Is it a100 % guarantee that the horse will never contract
the disease? No. But should the horse contract the disease
that they were vaccinated against usually it is a lighter
case than without the vaccination. Chances for recovery are
greatly increased with the vaccination than without. Vaccines
must also be stored, handled and administered properly. Not
doing so can mar the effectiveness of the vaccine.
Here are some of the diseases we vaccinate horses for:
Tetanus (Lockjaw): Tetanus occurs when a specific bacteria
enters a horse like a deep wound. As Tetanus grows it produces
a toxin and attacks the nervous system of the horse. Tetanus
Encephalitis: Horses can be attacked by three types of
encephalitis, Eastern, Western, and Venezuelan. Mosquitoes
carry this virus. Horses become infected by bites from infected
mosquitoes (usually found in states close to the Mexican border).
Encephalitis infects the horses' brain. If they survive they
may have permanent defects as a result. Encephalitis is potentially
Rabies: Infects the nervous system with a fatal infection.
Rabies is caused by a bite from an infected animal (such as
bat, raccoon, or skunk). Rabies can go undiagnosed in a horse
for a period of time and can actually spread the infection
to humans. This can happen by contact of body fluids with
broken skin (a cut on your hand).
Potomac horse fever: Generally confined to a specific
geographic areas (along the Potomac River) and in areas with
moderate climate and close to rivers. This disease is characterized
by depression, fever, diarrhea and founder. Check with your
vet or local extension agent for advice in your area.
Rotavirus diarrhea: Causing sever, potentially life-threatening
diarrhea in young foals. Rotavirus it appears is carried by
the mother (or passably another horse). The horses that pass
the virus may not develop problems but simply pass it on.
Pregnant mares can be vaccinated then they pass the antibodies
to their foals in the first milk (colostrum). Check with your
veterinarian about availability of this vaccine.
Influenza: This shows up like severe cold-like symptoms
and high fever making it a risk for developing bacterial pneumonia.
There can be periods when the virus mutates, causing epidemics
to break out. Vaccines are not completely effective in preventing
the disease since the virus can mutate easily. The vaccine
however can reduce the severity of the symptoms. Horses that
are most at risk to the flu are the very old, very young,
horses under stress, horses traveling, and horses stabled
where there is horse traffic.
Botulism: This is caused by toxin of a bacterium related
to the one that causes tetanus. Horses are highly sensitive
to it and many can die from this disease or the complications
brought on by this disease. If this disease is contracted,
treatment can be expensive.
Rhinopneumonitis: Also known as “rhino”. This disease
is like our “common cold”. The rhino virus can invade the
horses' nervous system causing paralysis, and can also cause
abortion. As with influenza, the risk factors are the same.
Every two months throughout pregnancy mares should be vaccinated.
Strangles: Routinely not done, strangles vaccination is
recommended for horses at high risk of exposure. Risk of side
effects from the intramuscular vaccine may be up to 30% for
this vaccine. This may include fever, loss of appetite, local
swelling, muscle stiffness and abscess formation at the vaccination
site. Vaccines usually provide reliable protection from severe
disease but only for a few months. It does not prevent the
disease completely. Unless there is known contamination on
the premises, shipping horses frequently or a lot of traffic
on and off the a farm, due to the side effects and limited
time it is effective, you should weigh the benefit for your
situation to vaccinate for strangles or not. That being said,
there is a type of strangles vaccine that is a spray into
the horse's nose. Intranasal vaccine has low incidence of
side effect. Protection is about the same. It is not clear
if intranasal vaccine for pregnant mares gets the needed antibodies
into the blood (protecting the foal with colostrum). It would
be wise to use the intramuscular vaccine with mares close
West Nile: This virus has caused many deaths in horses
in recent years in United States. It is transmitted by infected
mosquitoes. This virus infects the central nervous system
and causes symptoms of encephalitis. Signs of encephalitis
in horses include loss of appetite and depression, in addition
to any combination of the following signs — fever, weakness
or paralysis of hind limbs, muzzle twitching, impaired vision,
incoordination, head pressing, aimless wandering, convulsions,
inability to swallow, circling, hyperexcitability, or coma.
It is wise to vaccinate for this disease but avoid vaccinating
pregnant mares late in pregnancy. If you have a pregnant mare,
contact your veterinarian for a time best to vaccinate her
for your area.
Which diseases should you vaccinate your horse for? That depends.
You, with the advice of your veterinarian or your local extension
office, will need to make that decision. Getting the best,
up to date information from these sources will help you choose
About the Author
Fran Mullens has been a barn manager, trainer and riding instructor
for several years, and has worked with horses for nearly 25
years. Fran is co-author with Skimbleshanks the Farm Cat at
his blog. To learn more about the farm cat go to http://skimbleshanksthefarmcat.blogspot.com/.