Copper Poisoning, a Deadly Hazard for Sheep

Abstract

Copper (Cu) is an essential microelement for animals. However, sheep are particularly susceptible to Cu intoxication, a deadly disease reported worldwide. The risk of developing this poisoning is higher in vulnerable breeds and in intensively managed lambs or milk sheep. Two types of Cu intoxication can occur depending on the chronic or acute exposure to Cu. In chronic Cu poisoning (CCP), the most common form, Cu is accumulated in the liver during a subclinical period. A low intake of Cu antagonists (molybdenum, sulphur, iron, or zinc) favours Cu accumulation. The sudden release of Cu into the blood causes acute haemolysis with anaemia, haemoglobinuria, jaundice and death within 1-2 days. Acute Cu poisoning is related to the accidental administration or ingestion of toxic amounts of Cu. Acute oral exposure to Cu causes severe gastroenteritis, shock and death. Collapse and death occur shortly after parenteral administration. The diagnosis is based on history, clinical, gross pathological, histological and toxicological findings. Treatment of sheep with severe clinical signs often has poor success but is very effective during the Cu accumulation phase. Different therapies, based on either chelating agents or Cu antagonists, have been used to treat and prevent CCP.

Keywords: acute copper poisoning; anaemia; chronic copper poisoning; copper toxicity; hepatic copper accumulation; lamb; sheep.

Figure 1

Sheep. Clinical signs and gross pathology of chronic copper poisoning. (A) Reddish brown urine. (B) The subcutaneous connective tissue showing an intense yellow colour interpreted as marked icterus. (C) Kidney. Dark “gunmetal” colour of the kidney surface and the renal cortex. Note the yellowish colour of the fat in the renal pelvis. (D) Liver. The organ shows a slight increase in size with rounded margins and orange-yellow discoloration. Note the dilated gallbladder filled with dark bile. Image 1D courtesy of Professor V. Pérez, León University, Spain.

Figure 2

Sheep. Histopathology of chronic copper poisoning. (A) Kidney. The renal cortical tubular epithelial cells with vacuolated appearance, degeneration and necrosis. Note the orange-red hyaline material, interpreted as a haem compound, within the vacuoles of some cells. The same material is also found free within the lumen of renal tubuli. Haematoxylin and eosin. Obj. 40×. (B) Liver. Vacuolar degeneration and necrosis of the hepatocytes. Black round spots of different sizes, indicating copper granules, are found dispersed or condensed into the cytoplasm of hepatic cells. Note the dark yellow pigment within the bile canaliculi. Rubeanic acid stain. Obj. 40×. Image 2B courtesy of Professor V. Pérez, León University, Spain.