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Provet for educational purposes only.
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your veterinarian if your
horse (or pony) is ill as only he or she can correctly advise
on the diagnosis and recommend the treatment that is most appropriate for
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Strangles (also called equine distemper) is a highly infectious upper
respiratory disease which affects horses and ponies.
Causee cause of "strangles" is a bacterium : Streptococcus equi. The
disease is transmitted from infected horses (following direct contact with pus,
through aerosol spread due to coughing or the nasal discharge) and through
contamination of the environment.
The bacteria can be shed from an infected horse for over 6 weeks even though
the horse may not be showing signs.
The disease can affect any horse or pony that is exposed to an infected animal
or an environment contaminated with the bacteria.
The signs associated with strangles include :
- Soft tissue swellings in the neck - due to enlargement of the lymph
nodes. These can burst forming discharging abscesses.
- Nasal discharge - initially serous, but later mucopurulent
- General depression
- Anorexia; reluctant to swallow food due to pain
- Increased respiratory noise during breathing
Some horses may not show signs and may be carriers of the disease.
Occasionally horses develop an allergic reaction to Streptolysin O , a
toxin produced by the bacteria S.equi - a condition called purpura
haemorrhagica. 1-2 months following strangles they develop :
- Muscle pain
- Reluctance to walk or move head
- Oedema (fluid-filling) of the dependent parts of the body (the legs ,
and the underside of the chest, abdomen and prepuce in males)
- Weals (small lumps) over the body
- Haemorrhages of the visible mucous membranes (eg eyes, gums, vulva,
Most horses will recover fully from strangles, but death can occur -
usually as a result of complications.
ComplicationsThe bacteria can survive for long periods of time (months) in the
environment, and on objects such as buckets, tack, drinking troughs, and so
re-infection is likely in stables. Although the disease usually affects the
upper respiratory system, it can progress locally to involve the lungs
(pneumonia) or guttural pouch. Chronic recurrent cases and asymptomatic carriers
often have infection localised in their guttural pouches.
In some cases the infection may spread via the lymphatic system to
other parts of the body resulting in infection of lymph nodes in the
gastrointestinal tract, and even other organs, including the brain.
When strangles proves fatal. These complications are most likely to
occur in young foals with immature immune-systems or old debilitated horses.
Diagnosis can be made from the clinical signs and also from identifying the
organism by microbiological culture of pus, or swabs taken from the respiratory
tract. The guttural pouch may need to be examined using an endoscope, to confirm
The treatment of choice is antibiotics - usually penicillin. All infected horses
and in-contact horses should be isolated from other stock because the disease is
so contagious. In countries in which a vaccine is available this should be given
to suspect in-contacts which doe not develop signs of infection.
Treatment of purpura haemorrhagica involves :
- Long term antibiotics - penicillin - (weeks)
- Long term corticosteroids (weeks)
A vaccine is available in some parts of the world (eg USA) but it only
confers temporary immunity and can not be used for long term prevention of
Most horses will recover provided treatment is given as soon as possible.
Long term problems
A chronic carrier state or recurrent, chronic disease may be long
term problems if the guttural pouch becomes infected.
Updated October 2013