Introduction

• Cause: ingestion of Allium species including onions, leeks and garlic.
• Signs: signs associated with hemolytic anemia.
• Diagnosis: base on history, clinical signs and possibly the odor of onion or garlic on breath, feces or urine.
• Treatment: supportive.
• Prognosis: generally good with removal from source and supportive care.

Pathogenesis

Etiology

• Cattle appear to be particularly susceptible to Allium poisoning compared to goats and sheep.

Predisposing factors

General

• Cattle will readily eat Allium species, sometimes in preference to other forage.

Pathophysiology

• All parts of the plant are toxic.
• Trauma to the plants (chewing, crushing) converts organosulphoxides present to a variety of organic sulphur compounds including n-propyl disulphide, allyl propyldisulphide and allyl sulphide.
• n-Propyl disulphide, depletes the enzyme glucose-6-phosphate dehydrogenase (G6PD) within erythrocytes. The protective effect of the antioxidant, glutathione, is diminished as the glutathione remains in the oxidised state.
• Thiol free radicals and reactive oxygen species denature hemoglobin which precipitates within the cell resulting in the formation of Heinz bodies .
• Erythrocytes that contain Heinz bodies are fragile and more likely to lyse. They are removed from the circulation by the recticuloendothelial system, thereby inducing anemia.
• Free radicals produced by these processes oxidise hemoglobin to methemoglobin.
• In addition, the amino acids S-meth- and S-prop(en)ylcysteine sulphoxide (SMCO) are hydrolysed in the rumen to thiosulphate which is further metabolised to dipropyl disulphides and dipropenyl disulphides. These compounds are potent hemolytic agents.
• Cooking, dehydration or spoilage of Allium species does not reduce toxicity.

Timecourse

• Signs may occur suddenly within 24 hours if a large quantity has been ingested but it is more common for signs to occur after several days.
• Recovery usually occurs within a week, but can be longer in severe cases (up to 2 weeks).

Epidemiology

• Allium toxicosis may occur anywhere the plants are grown and typically occurs where cattle are fed a large quantity over a short period of time. 

Diagnosis

Treatment

Prevention

Outcomes