Protect
Your Horse Against Contagious Diseases
Few things
will protect your horse from the ravages of disease as easily and effectively
as immunizations. The vaccinations administered by your veterinarian to your
horse place a protective barrier between the animal and a whole list of problems:
tetanus, encephalomyelitis(sleeping sickness), influenza, rhinopneumonitis,rabies,
strangles, and Potomac Horse Fever, to name the most common.
Vaccinations
are a vital part of proper equine management. If incorporated into a program
that includes regular deworming, an ample supply of clean water, a good nutrition
program, and a safe environment, you and your horse will be all set to enjoy
many happy, healthy, productive years together.
WHAT
TO EXPECT
A good immunization program is essential to responsible horse ownership, but
just as in humans, vaccination does not guarantee 100% protection. In some situations,
immunization may decrease the severity of disease but not prevent it completely.
This is due to many complicated scientific reasons, such as differences in the
virulence or severity of some diseases (such as influenza).
Vaccination involves
the injection (with a sterile syringe and needle) of bacteria or viruses that
are inactivated or modified to avoid causing actual disease in the horse. Two
or more doses are usually needed to initiate an adequate immune response. Once
the immunization procedure is completed, the protective antibodies in the blood
stand guard against the invasion of specific diseases. Over time, however, these
antibodies gradually decline.
Therefore, a booster
shot is needed at regular intervals. Protection against some diseases such as
tetanus and rabies can be accomplished by boostering once a year. Others require
more frequent intervals to provide adequate protection.
VACCINATIONS
NEEDED
The specific immunizations needed by a particular horse or horses depend upon
several factors: environment, age, use, exposure risk, value, geographic location,
and general management.
Your local equine veterinary
practitioner can help you determine the vaccination program best suited to your
horse’s individual needs. The following diseases are those most often vaccinated
against. Again, your local practitioner will know what is best for your horse.
TETANUS
Sometimes called “lockjaw,” tetanus is caused by toxin-producing bacteria
present in the intestinal tract of many animals and found in abundance in the
soil where horses live. Its spores can exist for years. The spores enter the
body through wounds, lacerations, or the umbilicus of newborn foals. Therefore,
although not contagious from horse to horse, tetanus poses a constant threat
to horses and humans alike.
Symptoms include muscle
stiffness and rigidity, flared nostrils, hypersensitivity, and the legs stiffly
held in a sawhorse stance. As the disease progresses, muscles in the jaw and
face stiffen, preventing the animal from eating or drinking. More than 80 percent
of affected horses die.
All horses should be
immunized annually against tetanus. Additional boosters for mares and foals may
be recommended by your veterinarian. Available vaccines are inexpensive, safe,
and provide good protection.
ENCEPHALOMYELITIS
More commonly known as sleeping sickness,” this disease is caused by the
Western Equine Encephalomyelitis (WEE) virus or the Eastern version (EEE). WEE
has been noted throughout North America, while EEE appears only in the east and
southeast. VEE, the Venezuelan variety, has not been seen in the United States
for many years. However, a recent outbreak of VEE occurred in Mexico.
Sleeping sickness is
most often transmitted by mosquitoes, after the insects have acquired the virus
from birds and rodents. Humans also are susceptible when bitten by an infected
mosquito, but direct horse-to- horse or horse-to-human transmission is very rare.
Symptoms vary widely,
but all result from the degeneration of the brain. Early signs include fever,
depression, and appetite loss. Later, a horse might stagger when it walks, and
paralysis develops in later stages. About 50 percent of horses infected with
WEE die, and the death rate is 70 to 90 percent of animals infected with EEE
or VEE.
All horses need an EEE
and WEE vaccine at least annually. Pregnant mares and foals may require additional
vaccinations. The best time to vaccinate is spring, before the mosquitoes become
active. In the South and West, some veterinarians choose to add a booster shot
in the fall to ensure extra protection all year-round.
INFLUENZA
This is one of the most common respiratory diseases in the horse. Highly contagious,
the virus can be transmitted by aerosol from horse to horse over distances as
far as 30 yards, for example, by snorting or coughing. Signs to watch for are
similar to those in a human with a cold, i.e., dry cough, nasal discharge, fever,
depression, and loss of appetite. With proper care, most horses recover in about
10 days. Some, however, may show symptoms for weeks, especially if put back to
work too soon. Influenza is not only expensive to treat, but results in a lot
of “down
time” and indirect financial loss, not to mention discomfort for your horse.
Unfortunately, influenza
viruses constantly change in an effort to bypass the horse’s immune defense.
Therefore, duration of protection is short-lived and revaccination is recommended
every two to four months. Not all horses need influenza vaccination. However,
animals that travel or are exposed to other horses should be regularly immunized
against influenza. Follow your veterinarian’s advice as to whether your
horse needs influenza vaccine.
RHINOPNEUMONITIS
Two distinct viruses, equine herpesvirus type 1 (EHV-1) and equine herpesvirus
type 4 (EJ-IV-4), cause two different diseases, both of which are known as rhinopneu-monitis.
Both cause respiratory tract problems, and EHV-1 may also cause abortion, foal
death, and paralysis. Infected horses may be feverish and lethargic, and may
lose appetite and experience nasal discharge and a cough. Young horses suffer
most from respiratory tract infections and may develop pneumonia secondary to
EHV-1.
Rhinopneumonitis is
spread by aerosol and by direct contact with secretions, utensils, or drinking
water. Virus may be present but inapparent in carrier animals.
All pregnant mares
must be immunized. Foals, weanlings, yearlings, and young horses under stress
also should be vaccinated. Immune protection is short. Therefore, pregnant mares
are vaccinated at least during the 5th, 7th, and 9th months of gestation, and
youngsters at high risk need a booster at least every three months. Many veterinarians
recommend vaccinations at two-month intervals year-round.
OTHER
DISEASE THREATS
Several other diseases are common, although the need for vaccination against
them is a highly individual one. Rely on your veterinarian to guide you.
Other diseases include:
• Strangles. A highly contagious and dangerous disease. There may be some
side effects associated with vaccination; therefore, it is important to discuss
the risks versus benefits of vaccination with your veterinarian.
• Rabies. A frightening
disease which is more common in some areas than others. Horses are infected infrequently,
but death always occurs. Rabies can be transmitted from horses to humans.
• Botulism. Known
as “shaker foal syndrome” in young horses, this disease can be serious.
Botulism in adult horses, “forage poisoning,” also can be fatal. Vaccines
are not available for all types of botulism, but pregnant mares can be vaccinated
in endemic areas.
• Equine viral
arteritis (EVA). A complicated disease which can result in some breeding restrictions
and export problems. Follow your veterinarian’s recommendations.
• Potomac Horse
Fever. A seasonal problem with geographic factors. One third of affected horses
die. Contact your veterinarian.
IN
A NUTSHELL
For primary immunization, an initial vaccination is required, followed by a repeat
dose in 3-4 weeks. The following is a handy reference guide for scheduling your
horse’s immunizations:
• Tetanus. All
horses. Foals at 2-4 months. Annually thereafter. Brood mares at 4-6 weeks before
foaling.
• Encephalomyelitis.
All horses. Foals at 2-4 months. Annually in spring thereafter. Brood mares at
4-6 weeks before foaling.
• Influenza. Most
horses. Foals at 3-6 months, then every 3 months. Traveling horses every 3 months.
Brood mares biannually, plus booster 4-6 weeks pre-foaling.
• Rhinopneumonitis.
Foals at 2-4 months and younger horses in training. Repeat at 2- to 3-month intervals.
All brood mares at least during 5th, 7th, and 9th months of gestation.
• Rabies. Foals
at 2-4 months. Annually thereafter.
• Strangles. Foals
at 8-12 weeks. Biannually for high-risk horses. Brood mares biannually with one
dose 4-6 weeks pre-foaling.
• Potomac Horse
Fever. Foals at 2-4 months. Biannually for older horses. Brood mares
biannually with one dose at 4-6 weeks pre-foaling.
Many combination vaccinations
are available. Please check with your local equine practitioner.
Appropriate vaccinations
are the best and most cost-effective weapon you have against common infectious
diseases of the horse. A program designed with the help and advice of your local
veterinarian will keep your horses — and you — happy and healthy for
many years to come.
This brochure was developed
by the American Association of Equine Practitioners through a grant from Bayer
Corporation
Barer
Corporation, Agriculture Division,
Animal Health, Shawnee Mission, Kansas 66201
© 1994,1998 Bayer Corporation
E94122
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