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, West Nile virus 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. Recently intranasal vaccinations have
been developed for immunization against influenza and strangles. 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% 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 20-50% of horses infected with WEE die, and the death rate is
75-100% of animals infected with EEE. The mortality rate for VEE is 40-80%.
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 one month before mosquitoes become active. In the South and
West it is necessary to administer a booster shot every 4 months 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 to 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 3 to 6
months depending on the vaccine administered.
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 an influenza vaccine.
RHINOPNEUMONITIS. Two distinct viruses, equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4), cause two different diseases,
both of which are known as rhinopneumonitis. Both
cause respiratory tract problems, and EHV-1 may also cause abortion, foal
death and paralysis. Infected horses may be feverish and lethargic as well
as 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.
The 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 a minimum
during the 5th, 7th and 9th months of gestation, and youngsters at high
risk need a booster at least every three to four months.
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 rarely fatal
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. The mortality rate varies from 5 to 30%. Contact
your veterinarian.
West Nile virus (WNV). A neurological disease that
affects horses throughout the continental United States and is
transmitted through the bite of an infected mosquito. States with more
persistent mosquito populations may require more aggressive vaccinations along
with aggressive mosquito control techniques. Follow your veterinarian’s
recommendations.
IN A NUTSHELL
For primary immunization, an initial vaccination is
required, followed by a repeat dose in 3-6 weeks. The following is a handy
reference guide for scheduling your horse's immunizations:
·
Tetanus. All horses. Tetanus antitoxin; Foals from nonvaccinated mares should receive a dose of tetanus
antitoxin soon after birth. This induces immediate passive protection
that usually lasts 2 to 3 wks. Therefore, another dose of tetanus
antitoxin may be indicated on rare occasions where a foal has a penetrating
injury or surgery prior to starting the tetanus toxoid
series and > 3 wks after receiving the initial tetanus
antitoxin. It may be worth noting that a small but significant
number of horses experience serum sickness and fatal hepatic failure (serum
hepatitis) several weeks following vaccination with tetanus
antitoxin. Therefore, tetanus antitoxin should not be given without
discretion. Providing there has been adequate passive transfer of
antibodies via the colostrum, foals born to vaccinated mares should have
adequate levels of tetanus antibody and should not need tetanus
antitoxin. Tetanus Toxoid; Foals
from nonvaccinated mares: First dose at 3 - 4 months, second
dose at 4 - 5 months, third dose at 5 - 6 months. Foals from vaccinated mares: First dose at 6 months,
second dose at 7 months, third dose at 8 - 9 months.
· Encephalomyelitis. All horses. Foals from nonvaccinated mares: First dose: 3 to 4
months. Second dose: 4 to 5 months. Third dose: 5 to 6 months. Foals from vaccinated
mares: First dose: 6 months. Second dose: 7 months. Third dose: 8
months. Annually in spring thereafter and every 4-6 months in endemic
areas. Brood mares at 4-6 weeks before foaling.
· Influenza. Most horses. Inactivated injectable:
Foals from nonvaccinated mare:
First dose: 6 months. Second dose: 7 months. Third dose: 8 months, then at
3-month intervals. Foals from vaccinated mare: First dose: 9 months.
Second dose: 10 months. Third dose: 11 to 12 months, then every 3 months.
Broodmares: biannually, plus booster 4-6 weeks pre-foaling. Consult with
your veterinarian regarding the vaccine schedule for the intranasal
modified live version.
· Rhinopneumonitis. Foals first dose: 4 to 6
months. Second dose: 5 to 7 months. Third dose: 6 to 8 months, then at
3-month intervals and younger horses in training. Repeat at 3 to 4 month
intervals. All broodmares: at least during 5th, 7th, and 9th months of
gestation.
·
Rabies. All horses. Foals born to non-vaccinated
mares: First dose: 3 to 4 months. Second dose: 12 months. Foals born to
vaccinated mares: First dose: 6 months. Second dose 7 months. Third
dose: 12 months. Annually thereafter.
·
Strangles. Foals: Injectable:
First dose: 4 to 6 months. Second dose: 5 to 7 months. Third dose: 7 to 8
months (depending on the product used). Fourth dose: 12 months. Intranasal:
First dose: 6 to 9 months. Second dose: 3 weeks later. Biannually for
high-risk horses. Broodmares: biannually with one dose 4-6 weeks
pre-foaling.
·
Potomac Horse Fever. Foals first dose: 5 to 6 months. Second dose: 6 to 7
months. Semiannual for older horses. Broodmares: semiannually with one dose
at 4-6 weeks pre-foaling. Consult with your veterinarian if you are in an
endemic area.
·
West Nile virus (WNV). All Horses. Foals first dose: 3 to 4 months.
Second dose: 1 month later (plus 3rd dose at 6 months in endemic
areas). Broodmares: 4 to 6 weeks prepartum.
Annually thereafter prior to expected risk. In endemic areas vaccinate 2-3
times a year depending on risk.
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.
