dead sheep with a dodgy liver

Question 1

what are the differenetials for liver disease in sheep?

Answer 1

• Copper toxicity
  
  • Massive liver damage
  • May be acute or chronic
• Neoplasia
  
  • Rare but not unheard of, especially in older cattle
  • Lymphosarcoma and adenocarcinoma are seen
• Liver abscess
  
  • A.Pyogenes or Fusobacterium necrophorum – originate in rumen
  • Often follow rumen trauma, such as grain overload
• Hepatic necrosis
  
  • Fusobacterium invasion
  • Sometimes with jaundice
• Cholecystitis
  
  • Rare and hard to diagnose
  • More likely to result in jaundice than direct liver damage
• Chirrosis
  
  • Nearly always a result of fluke in cattle
  • Also ragwort poisoning, associated with encephalopathy and tenesmus
• Tuberculosis
  
  • Very rare manifestation
• Fatty liver syndrome
  
  • Discussed elsewhere – usually due to dietary imbalance pre-partum

(hepatic necrosis it is an end stage of liver abscess, caused by the same organism)

Question 2

What is seen in live/PM aminals with copper toxicity?
what are the laboratory results?

Answer 2

• Jaundice seen – of sclera and skin
• Urine – black in colour
• Liver – bronze coloured
• Kidneys – gun-metal appearance
  Presentation – anorexic, depressed, diarrhoea, abdominal pain, weakness, found dead

Clinicopathologic exam shows anaemia, haemaglobinaemia, increased liver enzymes and azotaemia.
Urinalysis – haemoglobinuria, isothenuria.
The combination of azotaemia and isothenuria indicates acute renal failure

Question 3

what are the two types of copper toxicity?

Answer 3

chronic:
* Results in organ change
* Much more common cause of death than copper deficiency in sheep
* Only ‘spills over’ to hypercupraemia when the storage capacity of the liver is exceeded
* Will then present as acute toxicity

Acute copper toxicity:
* Acute copper toxicity is seen after inadvertent over-administration
* Usually found recumbent or dead

Question 4

what is Cirrhosis?
when and how does it present?
what else can be seen with the main organism that causes cirrhosis?

Answer 4

• To all intents and purposes means chronic subacute liver fluke infestation
• Often present in early lactation when metabolic demands are highest
• Often present as constipated rather than Diarrhoea
• Can also see other clinical syndromes associated with the damage caused by the fluke including endocarditis, salmonellosis

Question 5

What compound cause the negative effects of ragwort poisoning (the ‘other’ cuase of cirrhosis)?
what is the pathogenesis of this?
what are the clinical signs?
how is ragowrt poisoning treated and prevented?

Answer 5

Ragwort poisoning - Pyrrolizidine alkaloids found in this plant, Senecio jacobaea or tansy ragwort

pathogenesis
- Direct hepatocellular damage by the alkaloids
- Speed of destruction and consequences depend on dose and duration
- Acute poisoning therefore rare as the functional reserve of the liver means that a lot can be destroyed before clinical signs are seen
- Slow, chronic ingestion is more common

Clinical signs:
- Weight loss
- Mild to moderate jaundice
- Photosensitisation
- Diarrhoea and low grade colic
- Hypoalbuminaemia may occur, with associated oedema
- Possible hepatic encephalopathy as ammonia levels rise around the brain

treatment and prevention:
- Adjust diet - Sheep can be less susceptible, so may even be able to tolerate ragwort at pasture in low doses
- Pull the plants before they flower and seed
- Do not make hay or silage from affected fields

• Treatment of clinically sick animals is unrewarding - They have overcome their hepatic threshold

Question 6

what is the pathogenesis of liver abscesses?
what is the treatment and prevention of liver abcesses?

Answer 6

• damage to the rumen through grain overload
• acidosis of the rumen
• rumenitis
• bacteria causing rumen abscesses
• bacterial emboli though the portal blood to the liver
• liver abcesses

Treatment is unrewarding

Prevention through avoiding acidotic ruminal conditions
- Feed enough roughage
- Do not over-feed grain
- Stimulate the rumen to ruminate, cudding to happen and so the brilliant buffering effect of saliva to be maximised

Question 7

what are the complication of liver abscesses?

Answer 7

• large abcesses cauing low grade colic
• liver unable to function
• Rupture into the abdominal cavity causing massive peritonitis
• Rupture into a major vessel causing major haemorrhage, shock and sudden death
• Vena cava thrombosis. (not as common)
  
  • peices of abcess usually settles where the vena cava passes through the diaphragm resulting in ascite
  • May result in pulmonary thromboembolism with pulmonary abscessation
    
    • This will give a painful cough and dyspnoea, probably with haemorrhage