Diarrhoea in horses Flashcards
What are the different mechanisms of diarrhoea?
- Malabsorption - loss of absorptive cells
- Increased secretion - active/passive
- Osmotic overload - feed, maldigestion
- Abnormal motility - inadequate mixing (stress)
5.Extravasion of fluid (oedema) - hydrostatic, colloid osmotic
What part of the intestine is affected with diarrhoea?
*Adults = LI always affected - disease of SI does not cause diarrhoea
*Foals = diarrhoea can occur with SI disease - fluid from SI overloads LI absorptive capacity (Rotavirus / Lawsonia)
What does chronic diarrhoea affect?
*All ages + all breeds - rarely life threatening
What happens with chronic diarrhoea in adult horses?
*Can progress from acute diarrhoea
*Many conditions of weight loss cause diarrhoea
*Only occurs with extensive colon damage
*Can have colonic pathology without diarrhoea
What are differential diagnosis of chronic diarrhoea in adult horses?
- Dietary causes - abnormal fermentation
- Dental disease
- Parasitism e.g. strongylosis
- Sand ingestion
- Antimicrobial associated diarrhoea
- Non-steroidal anti-inflammatory toxicity (right dorsal colitis)
- Non-gastrointestinal causes (kidney, liver, heart)
- Infiltrative disorders (inflammatory bowel disease)
- Neoplasia (e.g. lymphoma)
- Chronic salmonellosis
- Non – intestinal conditions (Liver disease, congestive heart failure, renal disease)
What should you find out about the horse’s history?
*management
*Diet + diet changes
*Exercise, travel + other causes of stress
*Deworming + other treatments
*History of recurrent episodes
*Diarrhoea in contact animals
What are clinical signs of chronic diarrhoea?
*No / mild dehydration
*Bright + eating well
*+/- weight loss
*+/- polydipsia
*+/- oedema
How would you investigate chronic diarrhoea? (tests)
*5 faecal samples for salmonella culture
*Faecal sample - parasites / sand
*Haematology + biochemistry
*Ultrasound
*Rectal / duodenal biopsy
-Diagnosis in <50% cases
How is chronic diarrhoea treated?
*Treat underlying cause
*Deworm - fenbendazole / ivermectin
*probiotics
*Anti-diarrhoeal medicines (ineffective long term)
Why does inflammation look black on ultrasound?
Oedema - fluid = black
What are causes of acute colitis in horses >9months old?
*Idiopathic
*Larval cyathostominosis
*Salmonella
*Clostridium difficile
*Drug-induced = antibiotics / NSAIDs
*Carbohydrate overload
*Sand
What are predisposing factors of acute diarrhoea?
*Antibiotic Tx - alters GI flora
*NSAIDs
*Transport
*Competition
*Hospitalisation
*Surgery
*ANY STRESS
What is endotoxaemia also known as in horses?
*Systemic Inflammatory Response Syndrome
‘SIRS’
What are presenting signs of SIRS?
*Depression
*Fever
*Tachypnoea / Tachycardia
*Purple MMs
*Slow CRT >2s
*Anorexia
*Dehydration
*Reduced GI sounds
*Colic
*Diarrhoea
What is the pathophysiology of acute diarrhoea?
*GI mucosal inflammation, ischaemia + reperfusion injury
*Breakdown of GI mucosal barrier = absorption of endo/exotoxins
*Fluid loss - malabsorption, excess secretion + loss of Na
How does SIRS occur?
1.Toxins = inflame colon
2.Enter hepatic portal vein
3.Overwhelm clearance mechanism of liver
4. Enter systemic circulation
5. SIRS
What does systemic toxins cause?
*Fever
*Inflammation
*DIC + haemorrhage
*Oedema
Shock
**Multi organ failure
What is the relevance of SIRS damaging extracellular matrix of laminae of the hoof?
Causes laminitis
What is the most common salmonella causing diarrhoea in horses? What are sources of infection?
*S. typhimurium
*Asymptomatic shedders / diseased horses
*Environmental factors - stressors (Transport, hospital, GI surgery, antibiotics)
How is salmonellosis diagnosed?
*Faecal culture
How is salmonella spread reduced?
*Isolation
*Disinfection
How is antibiotic induced diarrhoea treated?
*Withdraw antibiotics
*Supportive Tx
How is fluid therapy carried out?
*Determine dehydration + ongoing losses + maintenance = administer fluids
*Boluses of isotonic crystalloids
*Severe hypovolaemia = hypertonic saline rapidly
What are other supportive therapies?
*Treat SIRS = NSAIDs, Ice feet against laminitis
*Misoprostol
*Antibiotics
*Oral protectants
