Equine Flashcards
What can cause haemolysis in horses?
Neonatal isoerythrolysis
Infections
Drugs
Toxins
Autoimmune HA - relatively rare in horses
What are the two common causes of hyperbilirubinaemia in horses?
Anorexia
Acute hepatocellular disease
What percent of normal horses will look mildly icteric?
10-15%
What is the most common cause of icterus in horses?
Anorexia
What three things should be eliminated before thinking liver disease with an icteric horse?
Not anorexic
Not a foal
Not pale
What are the six functions of the liver?
Protein metabolism
Carbohydrate metabolism
Lipid metabolism
Detoxification
Immune system
Bile excretion
Why is hepatic disease not always followed by hepatic failure?
Liver has capacity to regenerate
Various functions giving varied clinical signs
What are the six common signs of liver disease in horses?
Depression
Anorexia
Colic
Abnormal behaviour
Weight loss
Icterus
What are the six less common signs of liver disease in horses?
Photosensitization
Diarrhoea
Bilateral laryngeal paralysis
Haemorrhagic diathesis
Ascites
Dependent oedema
Describe how photosensitization occurs with horses and how the liver is involved
Phylloerythrin formed by bacteria in gut
Absorbed, conjugated and excreted by the liver
With liver dysfunction increased levels of phylloerythrin
Exposure to UV light causes cell membrane damage and necrosis
Lesions occur in areas of non-pigmented skin as UV light absorbed more efficiently
What four things can be used to diagnose liver disease?
Clinical signs
Blood work
Ultrasonography
Biopsy
What are the three liver specific tests that can diagnose liver disease?
Increased bile acids
Increased SDH
Increased GGT
What percent of the liver can be imaged with ultrasonography in horses?
20%
What things could be seen on an ultrasonography in the liver in horses?
Dilated bile ducts
Choleliths
Abscesses
Neoplasia
What three things can a hepatic biopsy provide information for?
Diagnosis
Prognosis
Treatment options
What are the general principles for treatment of liver disease in horses?
Primarily supportive
Maintain animal until liver regenerates
With severe fibrosis regeneration unlikely
Correct fluid deficits and acid-base imbalances
Provide intravenous glucose if horse anorectic
Antibiotics if suspect bacterial aetiology
Anti-inflammatories
What is the treatment for hepatic encephalopathy in horses?
Sedation
Mannitol/hypertonic saline: cerebral oedema
Oral lactulose: limit ammonia absorption
Oral BCAA
What dietary modifications should be provided to a horse with liver disease?
High carbohydrate with limited protein
Protein rich in branched chain amino acids
Need to provide sufficient protein to ensure malnutrition does not occur
What are some recommended diets for a horse with liver disease?
Beet pulp
Cracked corn
Molasses
Sorghum, bran or milo
Oat hay
What anti-inflammatories can be provided to a horse with liver disease?
NSAIDs - flunixin meglumine
DMSO (dimethyl sulfoxide)
Corticosteroids - dexamethasone/prednisolone
Pentoxifylline
What is the main cause of pyrrolizidine alkaloid toxicity?
Ragwort poisoning
Describe the pathogenesis of pyrrolizidine alkoloid toxicity
Pyrrolizidine alkaloids metabolized by liver to toxic pyrrole derivatives
Pyrroles are antimitotic
DNA becomes cross-linked
Pyrroles bind to nucleic acid and proteins within hepatocytes
Cells can’t divide leading to megalocyte production
Proceeds to death and fibrosis
What are the clinical signs of PA toxicity?
Non-specific - diagnose upon biopsy with megalocytosis present
What is the prognosis for PA toxicity in horses?
Poor
Typically death within 10 days of clinical signs of liver failure
- Regeneration not possible if fibrosis present
What are the five causes of acute hepatitis in horses?
Theiller’s disease
Tyzzer’s disease
Toxic
Viral - equine herpesvirus infection
Parasitic - Parascarus equorum
What is the cause of Theiller’s disease in horses?
Unknown
What occurs with Theiller’s disease?
Widespread hepatic necrosis
Small liver at post mortem
What is the prognosis for Theiller’s disease?
Poor if severe hepatic encephalopathy
What causes Tyzzer’s disease in horses?
Clostridium piliformis
When is Tyzzer’s disease seen in horses?
Foals 7-42 days old
What are the clinical signs of Tyzzer’s disease?
May be none
Non-specific
Loss of suckle, depression and recumbency
Describe the treatment for Tyzzer’s disease
Antibiotics
Supportive therapy
What is seen with Tyzzer’s disease?
Multifocal hepatitis
Enteritis
What is the prognosis for Tyzzer’s disease?
Grave
What three things would present that are strongly suggestive of cholelithiasis and cholangiohepatitis?
Fever
Icterus
Colic
What are the three causes of stone formation in horses with icterus?
Parasites
Ascending biliary infection or inflammation
Biliary stasis
How can cholelithiasis be diagnosed in the horse?
Liver enzyme activity
- GGT
- SDH
- AST
Ultrasound
- Dilated bile ducts
- Cholelith
Biopsy
- Histopathology
- Culture
What is the threatment for cholelithiasis in horses?
Antimicrobials
Supportive care
DMSO
Anti-inflammatories
What is the prognosis for a horse with cholelithiasis?
Depends on:
- Fibrosis
- Number of choleliths
- Extent of choleliths
- Severity of clinical signs
Which horses is hyperlipaemia seen in most commonly?
Shetlands
Miniature horses
Other pony breeds
Which horses have an increased risk of hyperlipaemia?
Obese horses
How does hyperlipaemia occur and what may cause it?
Negative energy balance leads to hyperlipaemia
Caused by:
- Disease
- Stress
- Pregnancy
- Lactation
What are the clinical signs of hyperlipaemia?
Lethargy
Anorexia
Weakness
Icterus
Mild colic/diarrhoea
Recumbency
How can hyperlipaemia be diagnosed?
Breed
History
Clinical signs
Measure Tg in serum
How is hyperlipaemia treated in horses?
Reverse negative energy balance
- Encourage to eat
- Enteral nutrition
- Parenteral nutrition
Treat hepatic disease
- Supportive therapy
Eliminate stress
Treat concurrent disease
Inhibit further fat mobilization
- Restore positive energy balance
Increase triglyceride uptake by peripheral tissues
- Heparin as increases activity of lipoprotein lipase
What is the prognosis for a horse with hyperlipaemia?
Poor once severe clinical signs become apparent
How can hyperlipaemia be prevented in horses?
Monitor at-risk animals closely
Measure Tg levels in sick ponies
Ensure adequate nutrition
Prevent obesity
How will fasting a horse for 24 hours affect bilirubin levels?
Increases levels
