Page 494 - The Veterinary Care of the Horse

• the head of the tail may be raised

• poor performance and exercise intolerance
VetBooks.ir • an abnormally low head carriage

•
sweating
• abnormal brown pigment deposits on the retina of the eye

• cranial nerve problems

• laboured breathing.

Figure 11.7 Horse with equine motor neuron disease

Affected horses lose muscle and weight, despite having a normal appetite. There are two
recognized stages of the disease. In the subacute form, the symptoms develop quickly and

are very obvious. Some horses deteriorate rapidly and have to be euthanased. In 70% of
cases, however, after a period of 2–8 weeks, the condition stabilizes and the horses enter a
chronic stage where the trembling and muscle fasciculations subside and the horse may not

lie down as much. These horses still tire easily and fail to gain weight despite having a good
appetite. They may remain this way for months or years, or the symptoms may be slowly

progressive. A second, acute episode sometimes occurs 1–6 years later, necessitating
euthanasia of the horse. Some horses appear to develop the chronic form of the disease
without experiencing a subacute episode.