Page 512 - The Veterinary Care of the Horse

produce the toxin but horses are less likely to come into contact with these. The field maple

(Acer campestre), which is common in woods and hedgerows does not appear to contain the
VetBooks.ir toxin.

Outbreaks are most common on poor pasture in autumn and spring. Young horses are
considered to be particularly at risk. The onset of the disease can be very rapid and it may be

fatal.
The toxin causes muscle damage and affected horses are often unable to stand and have

difficulty breathing. The damaged muscle cells release the pigment myoglobin, which causes
dark urine and can damage the kidneys.

CLINICAL SIGNS

• stiffness
• weakness

• reluctance to move

• lethargy

• muscle tremors
• muscle pain

• sweating

• difficulty breathing

• shivering

• dark red or brown urine
• fast, irregular heart beat

• colic signs

• unable to stand

• sudden collapse and death.

DIAGNOSIS
Diagnosis is made on the clinical signs and confirmed by blood and urine tests. The grazing

history and presence of sycamore seeds or seedlings supports the diagnosis.

TREATMENT
Immediate treatment with intravenous fluids and intensive care is essential. Pain relief and

assisted feeding may be needed, as well as monitoring of the horse’s heart and lung function.
Affected animals often deteriorate for the first 24–48 hours so should be moved to an equine