Page 503 - The Veterinary Care of the Horse

ADULTS

Botulism can affect any age of horse and the symptoms vary from mild weakness to rapid
VetBooks.ir collapse and death, depending on the dose of toxin. The following signs may be seen.

•
An abnormally low head carriage.
• Loss of tongue tone and weakness or paralysis of the pharyngeal muscles often leads to
difficulties picking up and swallowing food. The horse may have a normal appetite but

only be able to chew very slowly. Saliva or food may drop from the lips or appear at the
nostrils. Affected horses often play with water but are unable to drink. If the tongue is

gently pulled forwards, there is less resistance than normal and the horse may be slow to
pull it back into the mouth.

• Bad breath from accumulated food retained in the mouth.

• Weak eyelid and tail muscles.
• Dilated pupils.

• A weak, short-striding and shuffling gait.

• Muscle tremors of the shoulder and flank muscles.

• Increasing weakness and fatigue.

• Lying down for long periods with increasing difficulty getting up.
• Difficulty breathing.

In the advanced stages, there may be paralysis of the bladder, little gut motility and
constipation. Respiration becomes increasingly difficult and the horse dies of respiratory

failure.

Diagnosis

The diagnosis is made on the history and the clinical signs. In the UK the disease is usually

associated with feeding big bale silage or haylage and it can affect a number of horses within
a group simultaneously.

A definitive diagnosis involves injecting mice with serum or plasma from the horse; if the
mouse becomes paralysed the diagnosis is confirmed.

Treatment

• Access to the source of the toxin should be stopped immediately

• Liquid paraffin or mineral oil given by stomach tube may reduce absorption of ingested