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Clinical signs

Within the literature, extensive reference is

made to EGS presenting clinically as one

of three forms: acute, subacute and chronic.

These are classified according to the duration

of disease however there is an inevitable

overlap between these sub-classifications

because disease duration is dependent on

severity, interventional factors, supportive care

and elective euthanasia.

The following clinical signs can be seen in

all cases of EGS:



Mild to moderate colic

Difficulty swallowing: (dysphagia)

(Figure 1)

High heart rate

Drooping eyelids (ptosis)

(Figure 2)

Patchy sweating

(Figure 3)

Muscle twitching

Dry, mucus covered faeces per rectum

Acute EGS (1-2 days):

Mild to moderate abdominal pain

Large volumes of nasogastric reflux

Small intestinal distension per rectum or

identified by an ultrasound scan

(Figure 4)

Subacute EGS (2-7 days):

Similar to acute cases but typically only

mild abdominal pain

Nasogastric reflux is not usually present

Chronic EGS (>7 days):

Weight loss leading to a greyhound,

tucked up appearance

Weight shifting of the hindlimbs, leaning

back against the walls

Inflammation and dryness of the nostrils


A presumptive diagnosis is usually made

based on the nature and progression of

clinical signs, recent clinical history,

epidemological information and the ruling

out of other differential diagnoses.

Gold standard diagnosis is based on

examination of nerve bundles found within

an intestinal biopsy that is taken during an

exploratory colic surgery. Unfortunately, this

is often a post mortem examination as a

suitable ante mortem test is still unavailable.

One test to aid diagnosis is the reversal

of ptosis (drooping eyelids) following

administration of (0.05%) phenylephrine

eye drops. Unfortunately, the sensitivity

and specificity of these tests are not

significant enough to be used solely in

the diagnosis of EGS.

Figure 3: Patchy sweating seen across

the body

Figure 4: Distended small intestine can be

identified ultrasonographically


Acute and subacute cases are associated

with a 95% mortality rate. However, fluid

therapy, analgesia and regular stomach

tubing can be initiated until a definitive

diagnosis can be achieved. At this stage,

euthanasia is recommended.

Chronic cases of EGS should be carefully

evaluated prior to euthanasia as up to 40%

can survive with appropriate nursing care.

The positive criteria to consider for chronic

cases includes:

Ability/willingness to drink and swallow


Absence of continuous moderate to

serious colic signs

Treatment of chronic EGS:

The major concern for the chronic cases

of EGS to overcome is the profound

inappetance exhibited. A picnic of highly

palatable, good quality feeds that are high

in protein and energy should be provided.

Feeding preferences of these horses often

change regularly so different options should

be available for them.

In some cases, horses can be hospitalised

and administered nutrition by either continual

flow system or within the fluids intravenously.

There is not sufficient evidence to show

whether these regimes will improve the

outcome of the case but they will reduce

weight loss and consequently increase the

time available for spontaneous improvement

in appetite to be made.

Nursing care:

Pain relief as necessary

Regular hand feeding

Regular short walks/turnout periods at


Antibiotics in cases where there is

evidence of feed inhalation to prevent

the development of inhalational


The nursing care of these cases requires

dedication, commitment and time from the

owner. It can take weeks to months for

improvements to be made and it is difficult

to predict whether the horse will survive

despite these efforts.

Research studies have shown that the

severity of swallowing difficulty, colic,

inappetance and rhinitis (inflammation of

nasal passages) is greater in non-survivors.

Cases which regain their appetite and their

body weight will often return to the same

level of strenuous exercise. However, even

in these cases, residual signs such as some

difficulty swallowing, intermittent colic and

coat changes can persist.


Last year, the Animal Health Trust, in

collaboration with the Universities of

Edinburgh, Liverpool and Surrey,

launched a randomised, placebo-

controlled field trial for a potential

vaccine. To qualify for inclusion with this

trial, horses must be kept at premises

that have been affected by at least one

EGS case within the preceding three

years. Horses are assigned to one of

two groups:

A vaccine group vaccinated with C

Botulinum Type C toxoid vaccine

A placebo group receiving inactive

placebo injection

The vaccine programme consists of three

injections at 21 day intervals, followed

by a booster vaccine at 12 months. The

horses remain under the care of their

normal veterinary practice and all visits,

vaccines, health checks are paid for by

the trial. The vaccine trial, if successful

will provide a major breakthrough in EGS

prevention. If you have suitable cases for

enrolment you are encouraged to contact

the EGS vaccine field team

at the Animal Health Trust



telephone 01638 555399)