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.

This quiz focuses on the comprehensive approach to managing equine diarrhoea, including understanding the physiological aspects of the equine hindgut. It covers differential diagnoses, clinical presentations, and recommends interventions based on your knowledge of equine health. Enhance your diagnostic skills and clinical reasoning in this specialized area.