Page 777 - The Veterinary Care of the Horse

Worms, e.g. cyathostomosis. A severe and potentially fatal diarrhoea may occur after
• anthelmintic treatment if large numbers of encysted larvae are present in the gut wall.

VetBooks.ir Large roundworm and tapeworms can also cause diarrhoea as can threadworm in young
foals.

• The use of antibiotics which lead to overgrowth of harmful bacteria such as Clostridium

spp. This is sometimes known as colitis X.
• Infection by bacteria, e.g. Salmonella spp.

• Viruses in foals, e.g. rotavirus.

• Tumours, e.g. lymphoma/lymphosarcoma.
• Infiltrative/inflammatory bowel diseases, e.g. granulomatous enteritis, eosinophilic

enteritis and lymphocytic/plasmacytic enteritis. In these conditions the intestinal wall

becomes thickened by infiltration of abnormal cells and this reduces its capacity to
absorb water and other nutrients.

• Poisoning, e.g. by acorns
• Drug toxicity, e.g. from longterm non-steroidal anti-inflammatory use, such as

phenylbutazone

• Severe dental disease in older horses
• Sand accumulation. This can occur when horses and ponies graze on sandy land or eat

hay in a sand school. It may also be a consequence of drinking from streams that reduce
to a trickle in the summer. The sand accumulates in the large colon and irritates the gut

lining.

• Peritonitis.

Clinical signs

Accompanying clinical signs are variable, depending on the cause of the disease. They can

include:

• increased gut sounds which may be audible from some distance
• weight loss

• depression

• loss of appetite

• dehydration
• colic

• faecal contamination and staining of the tail and hind limbs (Figure 17.13)