Download Strangles Horse Owner Fact Sheet Strangles (Streptococcus equi

Strangles Horse Owner Fact Sheet
Strangles (Streptococcus equi subspecies equi infection)
What is strangles?
Strangles is a highly contagious infectious disease caused by bacteria called Streptococcus equi
subspecies equi (S. equi). It is the most commonly diagnosed equine infectious disease in the United
Kingdom. It is an infection of the upper respiratory tract (nose and throat) and can cause abscesses
in the head region. Strangles is not usually fatal but can cause severe disease such as not being able
to eat or, rarely, struggling to breath due to the abscesses pushing on the airway. Rarely,
complications can occur such as bastard (metastatic) strangles, where abscesses can form elsewhere
in the body, and purpura haemorrhagica, where the body’s immune system starts attacking the body
tissues.
How is the disease spread?
The disease is spread either directly from horse to horse or indirectly via fomites. Direct infection
occurs by bacteria being shed in the discharge from the nose or abscess of an infected horse coming
into contact with a non-infected horse. Also importantly disease can come from the nose of horses
showing no signs of disease (shedders or carriers). Indirect infection occurs when the bacteria being
shed from the horse’s nose or discharge from an abscess is carried to other horses by any object,
such as people’s hands/clothing, tack, grooming and yard equipment (fomites). The incubation
period is up to 14 days, so there can be up to 21 days between cases showing signs of infection as
the abscesses can take up to a week to appear. All
horses are susceptible but young horses and sick
horses are more likely to show more severe signs.
Horses recovering from Strangles can shed the
bacteria for up to 6 weeks after recovering from
the illness and still pose a threat to other horses.
About 10% of horses recovering from the disease
will carry the bacteria within their head (in the
guttural pouches) and will be healthy horses, but
intermittently be a source of bacteria for months
to years that can infect other horses. Identifying
these carrier horses is key to stopping the
outbreak re-occurring on your yard and
preventing spread from yard to yard.
How do I know my horse has strangles?
Classical Strangles:
 Fever (above 38.5°C) accompanied with depression and loss of appetite.
 Profuse yellow nasal discharge from both nostrils (thick mucus)


Swellings on the side of the head and throat
which may burst and discharge pus. These
abscesses are usually hot and painful and
occur some days after the initial fever.
Sore throat – difficulty eating, extending the
head.
Atypical Strangles: (becoming more common
especially in healthy adult horses)
 Mild short term fever – may loose appetite for
a brief period of time.
 Mild clear nasal discharge.
 No abscess formation.
 These horses are a risk to other horses and should be treated as infectious.
 N.B. These clinical signs can be seen with a wide variety of diseases and not just strangles.
Isolating affected horses and seeking immediate veterinary attention is essential to stop the spread
of the disease.
Diagnosis:
Diagnosis of an individual horse is based on identifying the bacteria cultured (grown) in a lab from
throat swabs or aspirates/swabs from abscesses. However the bacteria is very difficult to grow and
will only be found in about 30% of cases. Therefore a molecular technique (PCR) can be performed
on the samples to increase the sensitivity of the test. However horses that do have strangles may
have negative results for culture and PCR; these horses will need another sample at your veterinary
surgeon’s discretion. If the horse has classical clinical signs or the bacteria has been already
identified on the yard laboratory confirmation may not be required at the attending veterinary
surgeon’s discretion. A new blood test (serology) is available that detects antibodies to the bacteria
The antibodies take up to two weeks to form and therefore the test cannot be used in the initial
stages of infection. The antibodies stay elevated for up to six months after infection and therefore a
positive test may not mean your horse has strangles at that moment, just that the horse has been
exposed to the disease in the last six months. Culture and PCR on swabs would be required to
confirm active infection. The blood test can be used to highlight potential carriers. To confirm a
horse is a carrier, endoscopy of the head (guttural pouches) is required and washes need to be taken
and submitted for culture and PCR.
Isolation:
Strict hygiene and disinfection protocols are
essential. Personnel and equipment that only
look after the isolated horses is ideal. Creating
an isolation area which has a foot dip and
specific overalls is important. Nothing that
enters the isolation area should leave the
isolation area without thorough disinfection.
Treatment:
If the diagnosis is positive either based on clinical signs, culture, PCR or blood test then your
veterinary surgeon will discuss treatment options with you. Most cases just need intensive nursing
care including rest and a dry warm environment. Feeding soft palatable feeds is important.
Abscesses can be hot-packed to encourage them to burst. Occasionally your vet may lance the
abscess to enable them to drain. Use of antibiotics in strangles cases remains controversial and
should be judged on an individual patient basis by the attending veterinary surgeon. However, most
horses do not need antibiotics. Severe cases may require antibiotics and using antibiotics in early
cases (e.g. those who have very recently spiked a fever) may be beneficial at your veterinary
surgeon’s discretion.
Control and Prevention:


Recovered horses can shed bacteria for at least 4 weeks. Maintaining isolation during this time is
critical.
At the end of this time screening the recovered horses for carrier horses is important (around
10% of affected horses may be carriers.) This can be done a number of ways depending on the
individual yard circumstances.
o Culture and PCR of three throat swabs (nasopharyngeal) 5-7 days apart
 Any horses returning positive results need guttural pouch lavage via endoscopy
o Culture and PCR of one guttural pouch lavage via endoscopy
o Serology blood test
 Any horses with positive results need guttural pouch lavage via endoscopy
Preventing strangles entering a yard:
 Isolate all horses for three weeks and monitor horses closely for a fever and nasal discharge.
 Consider performing serology blood test on all new horses moving on to a yard. Horses with
positive results should have one guttural pouch lavage via endoscopy and the fluid collected
submitted for culture and PCR.
 Equilis StrepE was a vaccine which is injected into the lip is now available again.
o Initial course is two injections 4 weeks a part.
o Then depending on the risk of disease to the yard of strangles then either 3 or 6 monthly
boosters. This should be determined in consultation with your veterinary surgeon.
o The vaccine can cause your horse to be unwell for 24 hours after vaccination and some
horses will need a small amount of antiinflammatory such as phenylbutazone
‘bute’.
o It is live bacterial vaccine and therefore
different to tetanus and influenza (‘flu’)
that horse owners in the UK are used to.
Therefore careful discussion with your
veterinary surgeon whether this
vaccination is appropriate for your yard.

A custom made prevention plan to which all members of yard agree to be devised by a
veterinary surgeon is the gold standard approach to preventing strangles. The prevention
strategies can vary and balance of risk against benefit – see risk assessment guide.
Risk Assessment Guide
Cool
Single horse
Hot
Multiple horses
No contact with other horsesOccasional contact with
horses of known health
status
No new arrivals into yard
New arrivals unusual
Multiple horses & owners
Large yard ; Livery yard
Regular contact with
horses of known health
status
New arrivals several
times each year
Frequent contact with horses
of unknown health status
No previous strangles
No previous strangles
Previous strangles; but
investigations for carriers
Annual health
plans/preventive
health plans in place
Quarantine of new
arrivals with testing
Quarantine of new
arrivals but no testing
Separate water troughs
No personnel traffic betweenLittle personnel traffic betweenPersonnel traffic
horses, biosecurity in place horses, with biosecurity
between horses, with
biosecurity
Communal water
troughs; shared feed
utensils
Personnel traffic
between horses, no
biosecurity
High risk (disease more likely
Low risk (disease unlikely)
Vaccination optional.
May be appropriate for
risk-averse owners
Frequent new arrivals;
high throughput of
horses strangles; no
Previous
investigations for carriers
No quarantine or testing
of new arrivals
6 month vaccination intervals
3 month vaccination intervals