Approach to equine diarrhoea Flashcards
Diarrhoea
faecal material with increased water content/increased volume/increased frequency
Pathophysiology of equine diarrhoea
Malabsorption surface epithelium
§ Atrophied villi
§ Disrupted sodium and chloride transport (water should flow in with Na and Cl)
Hypersecretion crypt epithelium
§ Inflammatory mediators and bacterial toxins -> endothelial injury loss of villi -> increased crypt epithelium surface area
§ Activation of cellular pathways -> water, chloride, sodium secretion
Hypermotility
§ Reduced transit time, stimulated by inflammation
Osmotic
§ Incomplete digestion of carbohydrates -> increased osmotic pressure in lumen
Endothelial dysfunction: increased hydrostatic pressure
§ Fluid from vasculature -> interstitium -> lumen
Clinical signs of equine diarrhoea
Pyrexia
Depression
Inappetence
Tachycardia
Tachypnea
Colic
…many present similarly regardless of causes
Viral causes of equine diarrhoea
Coronavirus
Bacterial causes of equine diarrhoea
Salmonella
Clostridia
Neorickettsia (Potomac horse fever)
(Lawsonia)
Parasitic causes of equine diarrhoea
Cyathostominosis
Iatrogenic causes of equine diarrhoea
NSAIDs
Antimicrobials
Dietary causes of equine diarrhoea
Diet change
Grain overload
Sand
Inflammatory causes of equine diarrhoea
Granulomatous
Eosinophilic
Lymphocytic/plasmacytic
Lymphoma
Non-GI, non-infectious causes of equine diarrhoea
Peritonitis
Liver disease
Toxic causes of equine diarrhoea
Acorns
Arsenic
Cantharadin
Equine coronavirus
Betacoronavirus, emerging pathogen
Apparently low fatality rate
Pyrexia of unknown origin, lethargy, anorexia
Diarrhoea, leukopaenia, colic
Diagnosis
○ Faecal PCR (transport on ice)
○ Population shedding low, +ve test likely to be relevant
Treatment/management
○ Supportive/symptomatic
○ Shedding for 2-5 weeks
Equine salmonellosis
Zoonotic
S. enterica (typhimurium, agona)
Faecal-oral transmission
Intracellular (enterocytes)
○ Evades the immune system
Host susceptibility increased by stress
○ Hospitalisation
○ General anaesthesia
○ Antimicrobial administration
Presentations of equine salmonellosis
Other than diarrhoea, salmonella is also associated with increased incidence of small colon impactions
Variable presentations
○ Severe acute colitis (classic)
○ Pyrexia, tachycardia, neutropaenia but no diarrhoea
○ Asymptomatic shedding
If they survive, may have chronic diarrhoea and protein loss
Diagnosis of equine salmonellosis
Faecal culture 30-50% sensitivity
PCR 98-100% sensitive
Five daily faecal samples
Treatment of equine salmonellosis
Supportive
Antimicrobials may not alter course of disease
§ Not a benign intervention
If chronic diarrhoea >4-5 weeks prognosis is poor
Equine Clostridia
Clostridium difficile, Clostridium perfringens
Gram +ve anaerobes
Zoonotic
Also identified in healthy horses
○ Toxin production important
Antimicrobial administration/nosocomial infection
Usually acute
○ May be found dead
○ Similar to other causes of enterocolitis
Diagnosis
○ Clostridial toxin ELISAs
§ C. difficile toxins A and B
§ C. perfringens enterotoxin/beta toxin
Treatment
○ Symptomatic
○ Metronidazole
§ Oral/per rectum if cannot tolerate
§ Appetite suppressant
Potomac horse fever
Neorickettsia risticii
Severe, very watery diarrhoea
Severe laminitis common
Treatment: oxytetracycline
Lawsonia
Obligate intracellular Gram -ve bacteria
Causes proliferation of crypt epithelial cells in the intestine (ileum initially)
Affects foals 2-13 mo (peaks 4-7mo)
But documented to affect horses up to 17yo – very rare
NSAID induced equine diarrhoea
Two manifestations
○ Right dorsal colitis
○ Generalised NSAID toxicity
Ulcerated mucosa, protein losing enteropathy
Anorexia, lethargy, fever, endotoxaemia, hypoalbuminaemia
Often inappropriate dosing - not always
Treatment
○ Symptomatic
○ Misoprostol
§ Synthetic prostaglandin analogue
○ Sucralfate
Antimicrobial induced equine diarrhoea
Some geographic element
○ Different antimicrobials/different regions
Association with C. perfringens, C. difficile, and S. enterica
Do not chop and change antimicrobials
○ Broader spectrum bigger effect on flora
Macrolides
○ Motilin receptor agonist as well as antimicrobial
○ Do not give to animals >5mo
Carbohydrate overload induced equine diarrhoea
Small intestine digestion overwhelmed -> large intestine
Rapid fermentation gram +ve lactic acid producing bacteria
○ ↓↓ pH
○ Lactic acid poorly absorbed = ↑ osmotic load
Death of gut microbial population -> endotoxin release
If severe -> mucosal ulceration
Laminitis
Viral causes of diarrhoea in foals
Rotavirus
Adenovirus
Coronavirus
Bacterial causes of diarrhoea in foals
Salmonellosis
Clostridiosis
Rhodococcus equi (1-4mo)
Lawsonia (weanling)
