Equine Diarrhoea Management

Approach to Equine Diarrhoea

• This presentation covers an approach to equine diarrhoea
• The presenter is Holly Lenagham, BVETMED, FHEA, MRCVS
• The presentation is for the University of Surrey
• The presentation is attributed to S. Kwon

Learning Objectives

• Apply core structure, function, and pathophysiology knowledge to common clinical scenarios
• Establish a holistic clinical approach to animals with diarrhoea, including detailed system-specific examinations
• Assess various clinical presentations, formulate differential diagnoses
• Develop diagnostic and prognostic skills for diarrhoea investigation
• Recommend appropriate medical/surgical interventions for diarrhoea management and disease prevention

Equine Hindgut Physiology

• The equine hindgut plays a key role in water storage and absorption
• It is the major site for water absorption
• Disruption in hindgut function can lead to diarrhoea
• The hindgut is a site of fermentation
• Fermentation produces volatile fatty acids, proteins, and vitamins
• It's susceptible to disturbance with large amounts of undigested sugars.

Equine Diarrhoea: Definition

• Definition: Diarrhoea is a symptom, not a disease, characterized by increased water content and frequency of faecal output
• Diarrhoea has various severities and clinical presentations

Equine Diarrhoea: Causes (Acute)

Acute Onset Diarrhoea

• Most acute cases are caused by infectious agents
• All horses: Salmonella spp., Clostridium difficile, C. perfringens, Aeromonas spp., Coronavirus, and larval cyathostomiasis (not in young foals)
• Foals and Weanlings: Foal heat diarrhoea, Rotavirus, Rhoddoccocus equi, Cryptosporidium, lactose intolerance, sepsis associated failure of passive transfer (FPT), Lawsonia intracellularis
• Non-infectious causes: antimicrobial-induced colitis, NSAID toxicity, grain overload, cantharidin, acorn, arsenic, sand enteropathy

Salmonellosis

• Gram-negative facultative anaerobes
• Horses are not carriers of Salmonella
• Equine cases often have few S. enterica serotypes
• Multidrug-resistant S. typhimurium DT104 and S. Newport are zoonotic
• Faecal shedding varies among groups and detection methods

Salmonellosis (Clinical Impact)

• Clinical impact varies based on exposure, virulence, and host immunity
• Subclinical case: usually non-pathogenic Salmonella spp.
• Mild infection: Fever, anorexia, depression, often with diarrhoea. Rapid recovery
• Acute enterocolitis: fever, anorexia, depression, diarrhoea, colic. Often has gastric reflux (gastric dilation and ileus syndrome)
• Septicemia/bacteraemia: endotoxaemia/SIRS, pneumonia, meningitis, septic arthritis, osteomyelitis
• Chronic case: following recovery from a severe infection

Salmonellosis (Diagnosis)

• Bacterial culture, faecal PCR, lateral flow test (multiple samples for sensitivity)
• Confirm isolates: antimicrobial sensitivity testing, serotyping, phage typing

Clostridiasis

• Gram-positive anaerobic spore-forming bacteria: the most common cause of nosocomial diarrhoea in horses
• Major toxins: Toxin A (enterotoxin), Toxin B (cytotoxin)
• Non-toxin-producing strains: Normal flora
• Faecal oral route: Opportunistic pathogens often linked to normal flora disturbance

Clostridiasis (Mechanism)

• Steps involve inhibitions, germmination, vegetative growth etc.

Equine Coronavirus (ECoV)

• Coronavirus family Group B enveloped ssRNA virus
• Faecal-oral route
• Clinical Significance is questioned. Often self-limiting; fatal cases reported with likely co-infections (e.g., salmonella, clostridia)

Larval Cyathostominosis

• Cyasthostomin (small strongyles/small redworm): A parasitic worm
• Clinical syndrome: Caused by mass emergence of encysted cyathostomin larvae from large intestinal walls
• Acute typhlocolitis with watery diarrhoea possible. Often a condition for young/old horses
• Seasonal (late winter and early spring)

Larval Cyathostominosis -Diagnosis

• Faecal tests: unreliable due to larvae being encysted
• Serum ELISA: Limited diagnostic value. Shows exposure but no current infection. False negatives possible.
• Can get false negatives.

Carbohydrate Overload

• Carbohydrates digested in the small intestine; excess entering the large intestine causes issues as too many VFAs and lactic acids lower the luminal pH
• Normal flora disturbance, pathogenic bacterial overgrowth, and endotoxin release are all possible outcomes

NSAIDs Toxicity

• NSAIDs routinely used in equine medicine; concern for inappropriate dosing or extended use; patient factors like dehydration or other illnesses
• Concern for equine gastric ulcers syndrome, right dorsal colitis (RDC)

Equine Diarrhoea: Clinical Findings

Dehydration and Hypovolaemia

• Diarrhoea can lead to substantial fluid loss
• Intra-cellular and extracellular spaces exist
• Various signs of dehydration including reduced urine output, tachycardia and impaired mucous membranes
• A large volume of fluid can be lost due to diarrhoea.

Protein Loss (Hypoalbuminaemia)

• Protein loss (especially albumin) from the gastrointestinal tract; resulting in signs of oedema
• Fluid imbalances, and other issues can also occur

Systemic Inflammatory Response Syndrome (SIRS)

• An exaggerated defence response to inflammation
• Clinical signs: Tachycardia, tachypnea, altered mucous membrane colour (e.g., white, brick red), pyrexia, delayed capillary refill
• Other signs include; reduced or absent urination, significant abdominal pain, ventral oedema, inappetence/weight loss, and potentially laminitis.
• Various possible causative factors include endotoxaemia, endotoxemic/septic shock, multi-organ dysfunction,
• A possible systemic reaction to bacterial infection.

Equine Diarrhoea: Clinical Signs (Chronic)

• Chronic diarrhoea: Signs can last for a few weeks or longer
• Often, the animal maintains hydration by drinking a lot. "Dirty hind" can be a clinical sign
• Weight loss another indicator

Equine Diarrhoea: Causes (Chronic)

• Inflammatory bowel disease (rare unless large colon involved)
  • Granulomatous, eosinophilic, lymphocytic/plasmacytic
• Lymphoma (rare unless large colon involves)
• Sand enteropathy
• Re-modelling of intestinal barrier from colitis/typhlitis (possible)
• Non-GI causes: Peritonitis, liver disease
• Inflammatory Bowel disease related to granulomatous, eosinophilic, lymphocytic/plasmacytic and Lymphoma

Equine Diarrhoea: Diagnostic Approach

• Thorough history taking (onset, duration, changes in feed or care, medication, exposure)
• Comprehensive physical examination (mentation, signs of pain, TPR, mucous membrane colours, gut sounds, hydration status)
• Laboratory work (PCV/TP, peripheral blood lactate, CBC, platelets, electrolytes, other organ functions)
• Faecal examination (eggs, PCR, bacterial culture etc.)
• Imaging such as Ultrasound and Radiography

Equine Diarrhoea: Management

• Fluid therapy: Type of fluid (crystalloids, colloids), volume and rate of replacement/maintenance
• Anti-inflammatory, pain relief
• Toxin absorbent
• Laminitis prevention
• Antibiotics
• Other specific treatment (e.g., probiotics, faecal transfaunation)
• Biosecurity
• Specific treatment dependent on the underlying cause (e.g., salmonellosis, clostridiasis, lawsonia infection)
• Medications like NSAIDS, steroid/s, and other specific medications
• Treatment using products such as Psyllium husk; +/- MgSO4 and removing sand.