Equine Diarrhoea - clinical problem solving

Equine Diarrhoea - clinical problem solving

• Define problem

• Define system

• Define location → small bowel or large bowel

Lesion is very difficult to narrow down

• narrow down differential list

Define problem

• unformed faeces → increased water content + increased frequency of defaecation

  • normal = formed faecal balls → usually 8-10 piles in healthy horse

• do not confudse with faecal water syndrome (unknown cause)

  • passing formed faeces surrounded by faecal water

• pathological mechanims

  • altered structure/permeability

    • inflammtion, infection, infiltration (neoplasia)

  • altered epithelial cell transport

    • salmonellosis → hypersecretion of fluid into gut

  • osmotic effects (esp foals)

  • altered motility

Define system

• GIT = primary organ system

• rarely other body systems affected

  • e.g. foals with septicaemia → then secondary localisation of bacteria TO the gut

Define location → small bowel or large bowel

ADULT diarrhoea

• large colon + caecum

  • primary site of water absorption and microbial digestion of carbohydrate and protein/non-protein nitrogen

• overwhelmed capacity of large colon to absorb fluid

• adult horse localises to large intestine → acute colitis

FOAL diarrhoea (large intestine yet to fully develop)

• often small (± all milk diet)

• sometimes large intestine

Narrow down differential list

• age?

• duration of clinical signs?

• history - presence of risk factors? (rule in & rule out)

Most common in UK

Neonatal (up to a month)

• foal heat diarrhoea

• rotavirus

• salmonellosis

• clostridiosis

• neonatal septicaemia

Weanlings (10-12 months)

• larval cyathostominosis

• proliferative enteropathy

Adults

• Larval cyathostoinosis

• Clostridiosis

• Salmonellosis

• Carbohydrate overload

• Sand enteropathy

• Equine coronavirus

• Dietary - lush pasture, not serious

Age?

Neonatal foals } up to 1 month [common in UK]

[what can you rule out in adults?]

• foal heat diarrhoea

  • normal, noninfectious change in microbiota

  • eating hay + mum’s faeces

• rotavirus

  • often in studs

  • not seen in adults (immunity develops)

  • foals - abundance of immature enterocytes

• salmonellosis → septicaemia + bacteraemia

• clostridiosis → septicaemia + bacteraemia

• neonatal septicaemia

  • failure of passive transfer- causes localised infection in gut

• less common causes

  • necrotising enterocolitis (NEC)

  • strongyloides westeri

  • dietary intolerances

  • cryptospoidium spp.

Weanlings foals } up to 10-12 months

• larval cythostominosis

  • thickening of large and small intestine

• proliferative enteropathy (lawsonia intracellularis)

  • obligate intracellular gram -ve bacteria

  • crypts of small intestine → immature enterocytes

  • thickened mucosa (SI + LI)

  • malabsorption + hypoproteinaemia (in pigs too)

• sand enteropathy

• salmonellosis

• clostridiosis

• rhodococcus equi enterocolitis

Adult horses

• larval cyathostominosis

  • encyst LI + caecum

  • immune related damage - mass emergence (temp + season)

  • PLE

• clostridiosis

  • C. perfringens + C.difficile

• salmonellosis

  • any horse age group

• carbohydrate overload

  • overeaten feed - absorbative capacity overload

  • high sugar in SI → enters colon → microbes ferment sugars

    • high gas (VFA) → high bacteria

    • damage to microbiota & gut wall → absorption of endotoxins

  • serious - never allow grain gorging

• sand enteropathy → abrasion of colon

• equine coronavirus

  • emerging disease in North America & UK

• dietary - lush pasture, not serious

• antimicrobial associated diarrhoea [ADD]

• NSAID induced ulcerative right dorsal colitis

• Inflammatory bowel disease

• Others

  • GI neoplasia

  • Potomac fever - not in UK

  • Peritonitis

  • Plant toxicosis

  • Blister beetle poisoning - North America

  • Undifferentiated/no differential diagnosis

    • → Colitis X

Duration of clinical signs?

Acute vs Chronic

History - presence of risk factors? (rule in & rule out)

• risk factors - next slide

Risk factors

• predispose horses to diarrhoea

1. Young performance horses → prone to acute

2. Previous antimicrobial + NSAID administration

   1. usually C.difficle → dysbiosis

3. Stressors or concurrent illness

   1. exhaustion, transport, recent illness,

   2. overcrowding, hospitalisation, surgery,

   3. high environmental temps

4. Recent deworming

   1. can lead to mass immune emergence of larvae (can present as acute or chronic)

5. Exposure to other horses/foals with diarrhoea

6. Poor foaling hygiene

   1. increases likelihood of contagious disease

   2. clostridia, salmonellosis, rotavirus

7. Failure of passive transfer in foals

   1. risk of septocaemia/bacteriaemia - then localises gut

Acute diarrhoea

• life-threatening disorder

• hypersecretion of fluid

• motility disturbances

• impaired mucosal barrier

• results in absorption of endotoxin

  • endotoxin build up → shock → death

• affected horses show abdominal pain, dehydration, CV shock

• severe diarrhoea, rapid clinical progression → medical emergency

Chronic diarrhoea

• mild + persisted for months

• bright, alert, responsive + remain hydrated

• clinical signs

• → weight loss + dependent oedema may be evident

  • decreased oncotic pressure → PLE

Diagnostic approach

Management - symptomatic + supportive

Diagnosis not important BUT
- contagious? zoontic?

- specific treatments → anthelminitcs in case of larval cyathostominosis

Localise disease process and guide treatment

History

Physical Examination

Bloodwork

• PLE - protein

• WBC 

  • inflammation

  • endotoxin

  • infection

  • diarrhoea associated with low protein

• Red cell count - dehydration

Abdominal Ultrasonography

• thick, odematous colon wall → suggests pathology of gut

Faecal panel PCR

Diagnositc tests that rule out differentials

• salmonellosis

• clostridiosis

• rotavirus

• equine coronavirus

• cyathostominosis

Salmonellosis

• S. typhimurium/anatum

• Faecal PCR or culture

• 3-5 serial samples → culture + PCR

  • 1 per day - intermittent shedding

  • determine negative disease status for Salmonella

• asymptomatic carriers exist in a NORMAL horse population

  • risk to immunocomprimised patients

  • carriers can be as high 10-20% of population

Clostridiosis

• C. perfringens Type A, C.difficle

  • diagnosis challenging because can be commensals

• Faecal culture + demonstrate toxin in faeces

  • toxin → ELIZA toxin assay, toxin gene PCR

Rotavirus

• Faecal electrn micorscopy, ELIZA or RT-PCR

Equine coronavirus

• Faecal RT-PCR

Cyathostomonosis (resistance to anthelmintics)

• faecal egg counts often negative

• cyathostomin larvae in faeces + circumstantial evidence

  • poor deworming history

• serological test → detects IgG(T) antibody (larval cyathostomin specific)