Copper toxicosis

Which of the following best explains why sheep are particularly susceptible to copper toxicosis?

• They have an enzyme that binds copper more efficiently.

• They accumulate copper in the liver over time with poor excretion.

• They lack the ability to absorb dietary zinc.

• They have low dietary protein requirements.

Answer explanation

Sheep have poor regulation of hepatic copper storage and inefficient biliary excretion. This leads to progressive hepatic accumulation, which may result in toxicosis upon sudden copper release.

What triggers the sudden release of copper from the liver in sheep with chronic copper toxicosis?

• Selenium deficiency

• High dietary calcium

• Exposure to nephrotoxic plants

• Stress events such as transport or starvation

Answer explanation

Stressful events like transport or starvation can trigger hepatic injury or cellular lysis, causing acute copper release and hemolysis.

Which of the following gross findings is most characteristic of hemoglobinuria in sheep?

• Kidneys with pale yellow streaks

• Cortical infarcts and glomerular scarring

• Gunmetal-blue kidneys with red-black stippling

• Multifocal granulomas on the renal capsule

Answer explanation

The "gunmetal blue" kidney appearance is a classic gross lesion in sheep with copper-induced hemoglobinuria

Which of the following best differentiates myoglobinuria from hemoglobinuria?

• Hemoglobinuria always presents with proteinuria

• Myoglobinuria is associated with skeletal muscle injury

• Myoglobinuria causes greenish urine

• Hemoglobinuria is never associated with dark urine

Answer explanation

Myoglobinuria results from muscle fiber damage and release of myoglobin, while hemoglobinuria stems from intravascular hemolysis.

Why is chronic copper poisoning still labeled "chronic" despite acute clinical signs?

• It always causes chronic kidney disease first

• It affects only older animals

• It is caused by inherited copper metabolism disorders

• It involves long-term accumulation of copper before an acute release

Answer explanation

The "chronic" label reflects prolonged hepatic copper accumulation, not the timing of clinical onset.

Which mechanism normally prevents copper toxicosis in sheep?

• Vitamin B12 enhances copper storage

• Copper binds to myoglobin for excretion

• Molybdenum in the diet forms complexes with copper in the gut

• Iron displaces copper from hepatocytes

Answer explanation

Molybdenum competes with copper for absorption and reduces its bioavailability in the gut.

Which breed is most associated with genetic copper metabolism disorders in dogs?

• Labrador Retriever

• Bedlington Terrier

• German Shepherd

• Beagle

Answer explanation

Bedlington Terriers often inherit a COMMD1 gene mutation that impairs copper excretion, leading to hepatic accumulation.

Which copper-binding protein is primarily responsible for safe hepatic storage of excess copper?

• Metallothionein

• Ceruloplasmin

• Hemoglobin

• Albumin

Answer explanation

Metallothionein binds copper in hepatocyte lysosomes, helping prevent toxicity unless overwhelmed.