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S T R ANG L E S
SUMMER 2011 ISSUE
EQUINE MATTERS
14
Diagnosis
The diagnosis should be confirmed by
growth and detection of the bacterium from
a naso-pharyngeal (throat) swab taken from
suspected animals. Pus can also be taken
from a discharging abscess. Blood samples
can be taken from horses to see if they have
been exposed to the infection. The blood
sample does not indicate if the animal is
affected at the time of sampling.
Spread of infection between
animals
Transmission of strangles requires fairly close
contact between infected and susceptible
horses. Spread can also occur through shared
water troughs and/or mechanical spread
through personnel and grooming kit etc.
The incubation period, that is, the period
between infection and signs being evident
varies from 7 to 14 days, though up to 21
days has been reported.
The main source of infection is carrier animals,
but the bacterium can survive for long periods
(up to 9 weeks) on wood if conditions of
temperature and humidity are optimal.
After infection, most animals will eliminate the
bacterium fairly quickly, however, a significant
proportion, perhaps 5-10% may not eliminate
the infection fully and become carrier animals.
The infection often remains dormant in the
guttural pouches of these animals.
The advice regarding the use of antibiotics
in the treatment of strangles remains unclear.
Opinions vary but in certain circumstances,
particularly those where horse welfare is
severely compromised, antibiotics will be
used, usually given by injection as the
affected horses are struggling to eat.
Treatment
Good nursing care is the mainstay of
strangles treatment:
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Keep water buckets clean and free
from mucus (this mucus runs down the
horse’s nose as it lowers its head
to drink)
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Keep the nostrils clean allowing them to
breathe more easily and smell food
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Encourage appetite with soft, easy to
chew foods that the horse is known
to like
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Non-steroidal anti-inflammatory drugs
(bute) can be given to reduce throat
inflammation
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Keep affected horses warm with
appropriate rugs
Prevention of future
outbreaks
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Consider a vaccination policy, the
vaccine is now available again
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Quarantine and testing of new horses
arriving on the yard
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Produce a ‘Health Plan’ for the yard
which details the strategy to cope with
any future outbreaks of strangles and
other infectious/contagious diseases
Managing an outbreak
Each situation will vary, but management
of an outbreak on a yard will likely involve
the following::
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Definitive confirmation that Strep.equi is
the causative bacterium and the disease
is, in fact, strangles
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Movement restrictions to limit horse
traffic on and off the affected yard
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Isolation of known affected cases
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Segregation of the non-affected horses
into two groups:
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Those that have been in contact with
affected horses, but are not yet
showing clinical signs
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Those that have had no contact with
affected horses
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As the outbreak runs its course - horses
may need to be moved between
these groups
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Blood testing of individuals to determine
if they have been exposed to the
infection
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Either naso-pharyngeal swabbing (three
swabs taken at 7 day intervals), or
endoscopic examination and flushing
of guttural pouches of those affected
horses to determine when they are free
of infection
The endoscope is a
small flexible camera
which can be used
in the investigation
of strangles
SUMMARY &
KEY POINTS
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Strangles is not a notifiable disease
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Strangles is not associated with bad
husbandry or poor management
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Rapid identification and diagnosis
with appropriate segregation leads
to quicker recovery times and
yard movement restrictions being
lifted sooner
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Horses appear quite ill, but the
vast majority will make a
complete recovery
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5-10% of affected horses will remain
carriers of the infection
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When the costs of an outbreak are fully
considered (see box below) vaccination
may be a worthwhile consideration
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One of the main obstacles to effective
control of a yard outbreak is owner
resistance to following infection
control procedures
Endoscopic exam to visualise
the guttural pouches
COSTS ASSOCIATED
WITH A STRANGLES
OUTBREAK
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Nursing time of sick horses
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Veterinary interventions: diagnostic/
laboratory tests and treatment
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Lost competition entries
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Loss of fitness due to lack of
work/lessons
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Lost income for those on yard
who work with horses on other
yards, e.g. farriers, instructors,
horse-transporters, dealers etc.