Core versus Risk-Based Vaccinations
Source: Southern Equine Veterinary Services, PLLC
Equine vaccines are divided into two
primary vaccination strategies:
Core Vaccines and Risk Based Vaccines.
Core vaccines pertain to t hose equine
diseases that are present within the
geographic region, are considered highly
infectious and potentially pose a risk of
sever disease in your horse. They are
diseases that we, as horse owners, have
the least amount of control over due to
environmental factors that are not easy
to control. These include:
 Eastern/Western Equine
 Encephalomyelitis (sleeping
sickness)
 West Nile virus
 Tetanus
 Rabies
Eastern/Western Equine Sleeping
Sickness are neurological diseases that
are spread by mosquitoes. Following
transmission from an infected mosquito,
your horse can develop symptoms of
severe neurological disease, which may
include death. Vaccines are effective in
prevention of the clinical disease.
Frequency of vaccination during the year
may depend on geographic location as
the more temperate climate has longer
periods of mosquito exposure, and
potential virus exposure.
West Nile Virus encephalomyelitis is a
neurological disease transmitted by
mosquitoes from infected birds. While
both Sleeping Sickness and West Nile
are transmitted by mosquitoes, due to
differences in the virus, vaccination
against sleeping sickness does not offer
cross-protection against West Nile.
Frequency of vaccination during the year
may also be affected by geographical
location and should be discussed with
your DVM.
Tetanus is caused C:\Documents and
Settings\Melissa\My Documents\vaccine
article.docby the bacteria Clostridium
tetanii. This bacterium is normally found
in the soil and can be introduced thru
contaminated wounds or abscesses.
Clinical signs include muscle spasms
and rigidity. Tetanus can be prevented
by appropriate vaccination and strategic
boostering following injuries.
Rabies is a neurological disease that is
considered 100% fatal in affected horses.
There is also the potential for
transmission from infected horses to
humans thru contact with infected saliva.
Rabies is transmitted to your horse thru a
bite from an infected warm-blooded
animal. Rabies vaccines are very
efficacious and usually are only required
annually.
Risk-based vaccinations are those
deemed necessary following a riskbenefit analysis discussion with your
veterinarian. These vaccinations will
vary depending on your geographic
location, the intended use (potential
exposure), as well as any specific unique
conditions or pre-existing issues which
may pertain to your horse. A solid
VCPR (veterinary-client-patient
relationship) helps you formulate the
need for risk-based vaccinations.
Examples of risk-based vaccination
protocol include (but are not limited to):
 Equine Herpes virus
(Rhinopneumonitis)
 Equine Influenza
 Strangles
Equine Herpes virus is spread thru
infected respiratory secretions and
contact with infected fetal fluids. Equine
Herpes can cause respiratory disease of
various severity, abortions in pregnant
mares, weak maladjusted foals at birth,
or a neurological form of disease. As
with other species of animals, the Herpes
virus may establish a unique latent
infection in horses. These horses may
shed the virus to susceptible animals
when their immune system is stressed,
making it difficult to control this disease.
There are vaccines with respiratory
disease and abortion claims, but none
that have a neurological claim. Vaccine
protocols, including choice of vaccines
and frequency, should be discussed with
your veterinarian.
Equine Influenza is a highly contagious
respiratory disease that is transmitted
thru infected respiratory secretions. The
severity of clinical signs depends on the
degree of existing immunity, as well as
the level of viral exposure. Clinical signs
include high fever, coughing, nasal
discharge, inappetence and lethargy.
Following infection with influenza a
horse should be rested for a minimum of
1 week for each day a fever of
103degreeF is experienced. Much like
human influenza, equine flu changed
with regard to its genetic make-up, but at
a slower rate than humans. Using a
vaccine with current influenza strains
will help prevent infection, as well as
decrease shedding of the virus from
infected horses. Frequency of
vaccination depends on the exposure
potential and should be discussed with
your veterinarian.
Strangles is highly infectious respiratory
disease caused by the bacteria
Streptococcus equi subspecies equi.
Following infection with the bacteria,
the bacteria reside and replicate within
the lymph nodes of the upper respiratory
tract. Clinical sign may include fever,
dysphagia (difficult eating), lymph node
swelling and abscessation, and thick
nasal discharge that contains the
bacteria. The disease is transmitted by
direct contact with infected horses or
indirectly through contaminated feed
bunks, water troughs, tack or
hands/clothing of caretakers. Strep equi
can exist for a period of time in the
environment when protected from direct
sunlight. Horse’s that have been
exposed, or recovered from the disease
may become intermittent shedders of the
bacteria and may infect other horses on
the premise. Current vaccines include a
modified-live intranasal and an
inactivated bacterial extract vaccine. The
type and/or necessity of Strangles
vaccination should be discussed with
your veterinarian.