1. What you need to know about
STRANGLES
What is Strangles?
Strangles (also equine distemper) is a highly contagious
upper respiratory tract infection caused by a bacterium,
Streptococcus equi, which
affects horses, ponies, and
donkeys of all ages. It is
often transmitted through
nasal discharge produced
from an infected horse. The
transmission can occur by
direct or indirect contact. The
disease can also spread when
material from draining abscess
contaminates pastures,
barns, feed troughs, stables,
etc. Equines of any age may
contract the disease, although
younger and elderly equine are more susceptible. Young
equines may lack immunity to the disease because they
have no had prior exposure. Elderly equines may have
a weaker immune system.
Clinical Signs
Infected horses quickly develop a high temperature (up
to 41°C) causing them to become depressed and go off
their food. In the following days the lymph nodes around
the throat enlarge due to abscesses forming in them.
These can result in respiratory obstruction and difficulty
swallowing, hence the name strangles. Although the
name sounds concerning,
complete respiratory
obstruction does not
occur. The abscesses
in the lymph nodes
may rupture of their
accord or may need to
be surgically opened
by your veterinarian.
Infected horses often
develop a nasal discharge
which may start clear
but becomes thick with
pus and often copious in
amount. They frequently
also develop a cough. In very rare cases, the bacteria
may affect other lymph nodes in the body and cause
abscesses to from throughout the horse’s body. This is
called bastard strangles and is usually fatal. Infected
horses can develop varying severity of clinical signs
and a nasal discharge without glandular swelling is
sometimes all that is seen. Younger horses (under the
age of 5) tend to develop more severe clinical signs.
Diagnosis
The diagnosis is relatively straightforward in horses
that develop the classical signs and is confirmed by
taking a swab from the back of the horse’s nasal cavity
(nasopharynx) or by directly swabbing a draining
abscess. There is also a blood test which can identify
whether horses have antibody (immunity) against the
strangles bacteria. High antibody levels indicate recent
infection including horses which are carriers and so
this is useful test for screening new horses coming into
a yard. In many cases the only accurate test is to take
a lavage from the guttural pouches. These are large
air-filled cavities which form part of the eustachian
tube. Using an endoscope we can enter the pouches
and flush them through with saline, collecting the fluid
that runs back out of the horse’s nose. This fluid can
be analyzed for both live and dead bacteria. This test
is particularly used for detecting carrier horses and
screening horses that have high antibody levels.

2. How it Spreads
Once strangles has entered a yard it can spread quickly
between horses either by direct contact or indirectly
through equipment or people. The bacteria are shed
in nasal discharge and in pus draining from open
abscesses. They can survive in the environment for
long periods and can survive in water troughs for at
least four weeks. Good hygiene is therefore essential in
controlling this
disease. The
bacteria infect
the lymph nodes
of a horse via
aspiration into
their respiratory
tract. Clinical
signs develop
within 3-14 days
after infection.
Treatment
Treatment of the individual patient is primarily supportive
nursing care. Your vet will administer non-steroidal
anti-inflammatory (NSAIDs) medication to control the
horse’s increased body temperature. NSAIDs work
on a chemical level. They block the effects of special
enzymes,specifically Cox 1 and Cox 2 enzymes. These
enzymes play a key role in making prostaglandins. By
blocking the Cox enzymes, NSAIDs stop your body
from making as many prostaglandins. This means less
swelling and less pain.
Antibiotics are not always used as they cannot
penetrate the abscess capsule and may slow down
the horse’s recovery by preventing the abscesses from
draining. The decision to give antibiotics depends on
the stage of the infection and will be decided by the
attending veterinarian. Applying a hot compress to the
enlarged lymph nodes may be advised to encourage the
abscesses to rupture, and after they have burst flushing
the cavity with antiseptic will be required until they have
healed. It will take several weeks for them to totally heal
up.
Control of Infection
The most important aspect to limit the spread of disease
is by maintaining strict hygiene and isolation of all
infected horses. Early detection of disease by closely
monitoring the body temperatures of in contact animals
are immediately segregating any suspected cases will
significantly reduce the number of horses that come
down with clinical disease. The use of gloves when
handling infected horses is paramount. Any equipment
belonging to the horse should not be shared and should
be throughly disinfected after use, including forks and
wheelbarrows used to muck out. The premises must
be isolated so that no in-contact animals leave the yard
and risks spreading the disease further. No infected or
in-contact animal should be released from isolation until
three negative nasopharyngeal swabs have been taken
over a two week period. Horses should not enter the
premises unless they can be kept in strict isolation away
from any possible source of infection.
Complications
Bastard Strangles
In very rare cases, the infection may spread to involve
lymph nodes and organs in other parts of the body
causing abscesses to form internally. This condition is
invariably fatal.
Purpura Haemorrhagica
This rare complication is characterized by red spots
forming on the skin and mucous membranes (such
as the gums) caused by bleeding from small blood
vessels under the skin, along with swelling of the limbs
and around the head. It occurs sporadically an is more
common in younger animals. Unfortunately it is often
fatal.
Chronic Carrier Status
A low number of horses can become chronic carriers
of the disease after infection. These horses harbor
the bacteria within their guttural pouches (part of the
Eustachian tubes) often in the form of chondroids
(calls of dried pus). Carrier status may be diagnosed
by blood test or endoscopic examination of the guttural
pouches to look for chondroids and to take washes for
bacteriological examination.
Prevention
All new horses entering the yard should be monitored
closely and any horse that develops a nasal discharge
must be isolated and tested immediately. If facilities are
available, new horses should ideally be kept in strict
isolation for two weeks. The people involved with caring
for the horses in quarantine must not move from the
isolated horses to others on the establishment. Both
intramuscular and intranasal vaccines are available.
Isolation of new horses for four to six weeks, immediate
isolation of infected horses, and disinfection of stalls,
water buckets, feed troughs, and other equipment
will help prevent the spread of strangles. As with any
contagious disease, hand-washing is a simple and
effective tool.