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EQUINE MATTERS
10
SPRING 2016 ISSUE
TETANUS
Figure 3. The third eyelid can be seen
protruding from the inside corner across
the eye
Figure 4. Spasming of the front leg
muscles makes grazing very difficult
Figure 5. A collapsed horse in the end
stages of the tetanus. This animal requires
euthansia on humane grounds
Clinical signs
Signs will develop between one and three
weeks following exposure to the bacteria,
though in most cases of disease, the initial
penetrating injury is never found. The entry
site is usually through deep puncture wounds,
but the spores may lie dormant in the tissues
for some time and produce clinical illness
only when tissue conditions favour their
proliferation.
The affected individual will initially become
nervous and extremely sensitive to external
stimuli. A stiff gait and muscle spasm will then
be evident. The third eyelid will protrude
across the eye
(figure 3)
and the tail head
may be held constantly in a raised position.
As the condition progresses, the neck, jaw
and throat muscles will spasm, leading to
difficulties in eating and drinking
(figure 4)
.
It is these signs that have led to the name
“lockjaw”.
In the late stages of the disease, the horse
will be recumbent and may have seizure
before death occurs due to paralysis of the
breathing muscles.
Treatment
This includes sedatives, antibiotics and large
doses of tetanus antitoxin although is usually
futile. Critically, all cases must be kept in a
quiet, non-stimulating environment and need
intensive nursing care. Most cases are not
noticed in the early stages and once
“lockjaw” is present, the horse will need to
be destroyed on welfare grounds
(figure 5)
.
The success of treatment is very poor. In my
20 year career, I have seen four cases of
tetanus and all have needed to be humanely
destroyed.
Prevention
A highly effective vaccine, given by
intramuscular injection, is available. The
primary course is two injections given
approximately one month apart. Most
vaccination manufacturers recommend an
initial booster is given a year later. Booster
vaccinations are then required every two or
three years, depending on the vaccination
used.
Tetanus vaccination is usually combined
with influenza vaccines, though they can be
given separately if influenza vaccination is
not required.
Vaccination of mares four to six weeks prior to
foaling will provide protection for the mare. If
the foal subsequently receives an adequate
supply of colostrum, the foal will be passively
immunised for the first ten weeks of life.
Key points
●
Prevention is highly
effective; treatment is not.
●
A vaccine is readily
available, relatively
inexpensive and very
effective.
●
There is no medical reason
why a horse should not be
protected from tetanus
through vaccination
.
What age can I begin to vaccinate
my foal?
Depending on the exact vaccine used,
foals can usually start their vaccination
programme from five to six months of age.
What should I do if I find a
wound on my unvaccinated
horse?
Clean the wound with water and possibly
diluted skin disinfectant, e.g. chlorhexidine
gluconate 4% (HiBiScrub, Molnlycke
Health Care Ltd.) and then call your vet.
Tetanus antitoxin can be administered to
the unvaccinated horse and this can give
passive protection (emergency vaccination)
against tetanus for three weeks.
A vaccination can be given at the same
time as the antitoxin, and a second dose
of the vaccine should be given four weeks
later. A third vaccination is then required
at least four weeks after the second
vaccination.
My horse has been vaccinated
for many years and is now
retired – do I need to continue
vaccinations?
Unlike in humans, there is no evidence as
yet that a given number of vaccinations
will lead to lifetime immunity. Vaccination
is always a choice weighing up the risks,
costs and as tetanus is a fatal disease
in horses, the risks are high for the
unvaccinated individual. It is not
uncommon for owners of older horses to
cease influenza vaccination for economic
reasons; however, influenza is not usually
a fatal disease.
Like most vets, I would recommend active
vaccination against tetanus for the lifetime
of your horse or pony.