Toxic causes of neurological conditions in ruminants

Question 1

Lead toxicity

Answer 1

• All species but most commonly seen in young (curious) cattle at pasture
• May have known history of lead contaminated soil (e.g. previous lead mining)
• Have a look in the field as part of your exam - may find lead contamination (e.g. car batteries, pre-1960s paint tins)

Question 2

Lead toxicity clinical signs

Answer 2

• Acute form - tremors, staggering, blindness, twitching of face, neck and ears progresses to seizures and death in 12-24hrs
• Subacute form (more common) – GIT dysfunction (rumen atony, constipation followed by foul-smelling diarrhoea). Dull demeanour, blindness, muscle twitching (less severe than acute form). Sheep show neurological signs less often than cattle. Death occurs in 3-4days.

Question 3

Lead toxicity: treatment

Answer 3

• Supportive care
  – Sedate animals with severe neurological signs
  – Provide IV fluid therapy
  – Remove animal from source of lead
• Chelation therapy
  – Calcium EDTA – 73mg/kg slow IV BID-TID for 3-5days
  – SEs include renal and gastrointestinal toxicity
  – Add thiamine (vit B1) at dose of 2mg/kg IM

Question 4

Hypernatremia

Answer 4

• Calves
• Excessive sodium ingestion in absence of adequate water
  – High sodium milk replacer with no water access
  – Electrolyte solutions
• Not common in the UK as typically use electrolyte solutions that are commercially available and therefore highly regulated

Question 5

Hypernatremia clinical signs

Answer 5

• Cerebral oedema -> muscle tremors, seizures, ataxia, opisthotonos
• May just have high mortality with no obvious neuro signs

Question 6

Hypernatraemia diagnosis

Answer 6

• Live calf = blood sample (Na > 160mEq/L)
• Dead calf = aqueous or vitreous humor
• Can also send brain (fresh and fixed)

Question 7

Hypernatraemia tx & prevention

Answer 7

• Difficult as can’t treat them very quickly: need to gradually phase down the [Na] -> consider euthanasia
• IV fluids -> formulate to match sodium concentration of calf and slowly reduce sodium concentration over several days
• Prevention: ensure free water access and be careful with electrolytes (especially homemade)