7.1.4: Causes of diarrhoea Flashcards
What are some differentials for acute diarrhoea in the adult horse?
- Salmonella spp.
- Clostridium difficile
- Clostridium perfringens
- Coronavirus
- Cyathostomiasis
- Antimicrobial-associated
- Right Dorsal Colitis
- Grain overload
- Dietary
What are some differentials for chronic diarrhoea in the adult horse?
- Salmonella spp.
- Cyathostomiasis
- Right Dorsal Colitis
- Sand enteropathy
- Inflammatory Bowel Disease
- Dietary
What clinical signs and complications might you see in a young or adult horse with acute diarrhoea?
- Cow pat to high volume hosepipe diarrhoea
- Quiet to depressed demeanour
- Colic
- Fever
- Hypovolaemia
- Might also see: SIRS, laminitis, secondary infections
These cases have a significant risk of deteriorating rapidly.
What clinical signs and complications might you see in an adult horse with chronic diarrhoea?
- Cowpat to high volume hosepipe diarrhoea
- Bright to depressed demeanour
- Colic
- Fever
- Ventral oedema
- Weight loss
- Electrolyte imbalances
- These horses are often normovolaemic
Describe the pathogenesis of antimicrobial-associated colitis
- Disruption of GI flora -> lack of competition for nutrients
- This allows pathogenic bacteria to proliferate
- The obligate anaerobe population of the flora is most important -> antibiotics affecting these have a higher incidence of causing diarrhoea
True/false: cyathostomiasis can cause prepatent disease.
True
When is cyathostomiasis most commonly seen?
In spring due to sudden mass emergence which produces clinical disease
What is the cause of right dorsal colitis?
- NSAID toxicity
- This is often in horses receiving higher than licensed doses, but can still occur with normal doses over a short time
- This can occur in the normovolaemic horse
Describe how grain overload leads to diarrhoea in the adult horse
- Horses gain access to large quantity of hard feed
- Small intestinal digestion is overwhelmed and soluble carbohydrates enter the large intestine
- Rapid fermentation occurs by lactic acid-producing bacteria. This lowers the pH and kills off gram negative bacteria.
- Endotoxin is released when bacteria die
- Other bacteria overgrow and the gut wall becomes compromised
- –> bacteria and toxins enter circulation
Describe how clostridiosis causes diarrhoea in the adult horse
- Clostridiosis is most commonly antimicrobial-associated and nosocomial
- Clostridia are part of the normal flora in all ages, and are present at low numbers without producing toxins
- When these bacteria produce toxins, disease is seen
- Most commonly: Clostridium difficule, Clostridium perfringens
True/false: all Salmonella serovars are zoonotic and affected animals shed constantly.
False
* Not all serovars are zoonotic but some are so need to be aware of this.
* There is intermittent shedding by infected animals.
What clinical signs might you associated with Salmonella infection in adult horses?
- Large volume watery diarrhoea
- Lethargy
- Pyrexia
May see bacteraemia.
True/false: coronavirus can be associated with outbreaks of diarrhoea in adult horses.
True
What are risk factors for sand enteropathy?
- Pasture access on sandy soil
- Overgrazed pastures
- Fed on the ground
Sand ingestion is commonly associated with acute intestinal obstruction, but can also cause…
abnormal accumulation of sand in the large intestine (–> chronic diarrhoea)
What are some risk factors for salmonellosis in adult horses?
- Recent abdominal surgery
- GI disease e.g. small colon impaction
- Immunosuppression
- Antibiotics
- General anaesthesia
- High ambient temperatures
- Prolonged hospital stay
- Horses actively shedding or carriers
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What types of inflammatory bowel disease are there?
- Multisystemic eosinophilic epitheliotropic disease (MEED) / Eosinophilic enteritis (EE)
- Granulomatous enteritis (GE)
- Lymphocytic-plasmocytic enteritis (LPE) or colitis
- Lymphosarcoma
Pathogenesis of Clostridiosis in horses
- Most commonly antimicrobial-associated and nosocomial
- Clostridia are part of the normal flora in all ages; usually exist at low numbers and do not produce toxins
- When toxins are produced there is disease
- Clostridium difficile, Clostridium perfringens
Differentiate between the types of Clostridia that cause diarrhoea in horses
C. difficile = more common
* Often associated with antimicrobial-associated colitis
* Could be a reservoir for human Clostridium difficile infection
C. perfringens
* Type A and C are most common
* Toxins produced lead to disease
* Seen with haemorrhagic disease, mainly neonates but can be adults too
Risk factors for Clostridiosis
- Dietary changes
- Hospitalisation
- Antimicrobials
- GI disease
- (Not fully understood)
Characteristics and risk factors of coronavirus
- Recently emerged as an enteric pathogen in horses
- Can be associated with outbreaks
- Risk factors not fully understood
Epidemiology of cyathostomiasis
- Most important equine parasitic disease: high prevalence and can have severe clinical signs
- Causes pre-patent disease
- Most commonly in spring; in hotter climates, mostly seen in autumn
What is the difference between Cyathostomins and small strongyles?
They are the same thing
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The life cycle of which parasite is shown here?
Cyathostomins (small strongyles)
How do cyathostomins cause disease?
- Sudden mass emergence leads to clinical disease
- There is mucosal injury, ulceration, and inflammation
Risk factors for cyathostomiasis
- Age
- Season
- Period since last anthelmintic
- Altered host immunity
- Stress
- Dietary change
- (Some factors unknown)
What is antimicrobial-associated diarrhoea and how does it develop?
- Occurs as a side effect of antimicrobial administration: there is disruption of GI flora, lack of competition for nutrients, and pathogenic bacteria / those normally found in low numbers can proliferate
- Obligate anaerobe population of the flora is most important in preventing this from happening (antibiotics affecting these have a higher incidence of causing diarrhoea)
- Consider if patient really needs antibiotics before prescribing and follow PROTECT ME guidelines
Which are more susceptible to Right Dorsal Colitis: horses or ponies?
Ponies are more susceptible to NSAID toxicity and right dorsal colitis
Pathogenesis of Right Dorsal Colitis
- Toxicity from NSAID administration
- NSAIDs interfere with prostaglandins needed for colon health -> interfere with GI blood flow and protective mechanisms e.g. mucus production
As well as Right Dorsal Colitis, what other side effect(s) can NSAIDs cause in adult horses?
Medullary crest necrosis
Risk factors for Right Dorsal Colitis
NSAID use
* Can occur with normal dose, but often seen if higher than licensed doses are used
* Does not need to be long term use
* Can happen in normovolaemic horses at normal doses!
* More common with oral phenylbutazone, less common with COX-2 selective drugs
Pathogenesis of grain overload
- History of horses gaining access to large quantity of hard feed
- Small intestinal digestion is overwhelmed and soluble carbohydrates enter large intestine
- Rapid fermentation of carbohydrates by lactic acid-producing bacteria lowers pH
- Gram negative bacteria die and large quantities of endotoxin are released
- Other bacteria overgrow and gut wall becomes compromised
- Bacteria and toxins enter circulation
Clinical signs of grain overload
- SIRS
- Osmotic diarrhoea due to lactic acid being poorly absorbed
- Severe (often fatal) laminitis
Risk factors for grain overload
- Access to large quantity of grain
Amount needed to cause diarrhoea varies but horses fed diets high in soluble carbohydrates are more resistant
General risk factors for infectious GI disease
- Existing GI disease
- Immunosuppression
- General anaesthesia
- Recent abdominal surgery
- Antimicrobials
- Hospitalisation
- Other horses
- Dietary changes
Differentials for acute diarrhoea in young (6 weeks-9 months) horses
- Salmonella spp.
- Clostridium difficile
- Clostridium perfringens
- Coronavirus
- Cyathostomiasis
- Antimicrobial-associated
- Right Dorsal Colitis
- Grain overload / dietary
- Equine Proliferative Enteropathy
- Rhodococcus equi
Causative agent, signalment and pathogenesis of Equine Proliferative Enteropathy
Causative agent: Lawsonia intracellularis
Signalment: 2-8 months old
Pathogenesis: proliferative enteropathy of small intestine leading to severe hypoalbuminaemia and weight loss +++
Characteristics of Rhodococcus equi
- Usually see respiratory disease
- Diarrhoea is an uncommon manifestation
Risk factors for Lawsonia intracellularis and Rhodococcus equi
- Often geographical: farms with a history of disease often see annual reoccurence in the given age group
Differentials for chronic diarrhoea in the young horse
- Salmonella spp.
- Cyathostomiasis
- Right Dorsal Colitis
- Sand enteropathy
- Inflammatory Bowel Disease
- Dietary causes
- Lawsonia intracellularis
- Rhodococcus equi
Which anatomical regions are implicated in neonatal diarrhoea compared to juvenile and adult horses?
- Neonatal diarrhoea - small intestinal pathology only (neonate starts really ingesting roughage around 6 weeks of age)
- In juvenile / adult horses - large intestinal pathology required (± small intestinal pathology) in order to result in diarrhoea
How old is a neonate and how is the neonatal period divided?
Neonate: 0 days - 6 weeks
First period: 0-10 days
Second period: 10 days-6 weeks
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Risk factors for development of diarrhoea in neonatal foals
- Failure of passive transfer
- Pre-existing disease
- Poor hygiene in the peripartum period
- High stocking density
- Antimicrobial administration
- Milk replacer therapy
Diagnostics and treatment for diarrhoea in neonatal foals
Diagnostics
* History and physical exam
* Haematology and biochemistry
* Further diagnostics: ultrasound, faecal cultures, PCR
Treatment
* Treat the underlying cause
* Treat the consequences of diarrhoea: fluid/ electrolyte loss, bacterial translocation, albumin loss, nutrition
