Page 871 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

846 CHAPTER 4

VetBooks.ir likely to be exposed in spring and autumn in tem- CHRONIC DIARRHOEA
perate climates, and winter in subtropical climates.
Annual or biannual deworming may suffice on farms Definition/overview
with a reasonable stocking density and good manure Chronic diarrhoea is the continuous or intermit-
management. Other farms may require more fre- tent passage of soft or watery faeces for a prolonged
quent deworming. Multiple anthelmintic-resistant period of time. Horses of all ages can be affected. It is
small strongyles are a serious concern. a relatively common and often frustrating problem.
Management factors such as stocking density,
manure management and pasture rotation need Aetiology/pathophysiology
to be assessed. Ideally, manure should be removed There are a variety of possible causes and most cases
from pastures twice weekly to prevent accumula- are idiopathic. Inflammatory, infectious, neoplastic
tion of infective larvae. Harrowing of pastures may and nutritional causes are all possible. The patho-
also be effective in hot and dry weather as the infec- physiology is variable, depending on the specific
tive larvae are susceptible to dessication. Ruminants aetiology. The net result is intermittent or continu-
are resistant to small strongyles, so pasture rotation ous passage of soft faeces because of a disruption
with these species is useful if practical. of the normal fluid homeostasis mechanisms in the
large colon. Small-intestinal disease may be pres-
Prognosis ent concurrently, but small-intestinal disease alone
It has been reported that approximately 40% of should not produce diarrhoea in an adult horse.
horses with larval cyathostominosis will survive if
given appropriate treatment. Some horses will die Clinical presentation
within 2–4 weeks of initial clinical signs; however, Intermittent or continuous passage of soft faeces
this is complicated by the difficulty in diagnosing is often the only clinical complaint. Other clini-
cases. A prolonged recovery period may be required cal abnormalities, including weight loss, ill-thrift,
in some cases depending on the degree of mucosal anorexia, peripheral oedema, depression and fever,
damage. The prognosis is poorer if clinical signs may be present and suggest more severe underlying
have been present for more than 3 weeks. disease.

Differential diagnosis
Table 4.12 Diagnostic options for chronic diarrhoea A variety of infectious, inflammatory, neoplastic and
nutritional causes exist. Specific diseases are covered
• Haematology under their appropriate sections. Occasionally, non-
• Complete blood cell count
• Serum biochemical profile intestinal diseases such as liver disease, Cushing’s
• Plasma fibrinogen disease and hyperlipidaemia may cause chronic
− Serum amyloid A diarrhoea.
• Faecal analysis
• Salmonella culture Diagnosis
• Clostridium difficile toxin A/B ELISA A thorough history should be obtained in order to
• Clostridium perfringens enterotoxin ELISA characterise the changes in faecal consistency, in
• Faecal float and smear particular to try to make an association between
• Abdominal radiography diarrhoea and certain management areas such as
• Abdominal ultrasonographic examination feeding, exercise, travel or drug therapy. A variety
• Rectal mucosal biopsy of diagnostic tests can be performed to identify the
• Culture aetiology (Table 4.12). Investigation of undifferenti-
• Histology ated IBD as a key differential is warranted in cases
• Carbohydrate absorption tests refractory to dietary management and non-specific
• Exploratory laparotomy/laparoscopy with biopsies therapy.