Introduction

• A large plant group of mostly perennial bulbous herbs with characteristic aroma.
• Group includes onion, spring onion, shallots, field garlic, garlic, chives, leeks, wild or wood garlic, crow or false garlic.
• All parts of the plants should be considered toxic.
• The onion (Allium cepa) is the most significant toxicologically in dogs.
• Signs: gastrointestinal effects, dehydration and subsequent development of hemolytic anemia and Heinz body formation.
• Diagnosis: signs and case history.
• Treatment: gastric decontamination if appropriate, with symptomatic and supportive care. Emphasis on addressing a potential hemolytic anemia.
• Prognosis: fatal cases are rare, even in dogs with predisposing factors.

Pathogenesis

Etiology

• Ingestion of plants or plant extracts.
• Note that cooked plant material may still be hazardous.

Predisposing factors

General

• Some dogs appear particularly susceptible to ingestion of plants from this group.

Specific

• Some dogs appear at greater risk. These dogs possess erythrocytes with inherited high sodium-potassium ATPase activity, high potassium and low sodium concentrations, in addition to accumulation of reduced glutathione, glutamate, and aspartate (HK dogs).
• These dogs are more likely to develop severe hemolytic anemia and methaemoglobinemia.
• These severe clinical features may have an early onset (1-2days) in these dogs.

Pathophysiology

• Toxic mechanism not fully elucidated and probably multifactorial.
• Toxins are thought to be a group of structurally similarn-propyl disufides and thiosulfinate compounds.
• N-propyl disulphide depletes glucose-6-phosphate dehydrogenase (G6PD) within erythrocytes diminishing the protective effect of glutathione, as this remains in its oxidized state.
• In this state glutathione forms mixed sulphide bonds with hemoglobin and precipitates within the cell resulting in the formation of Heinz bodies.
• These affected cells are usually removed from circulation by the reticuloendothelial system, thereby inducing anemia.
• There is evidence to suggest that there are other oxidative extracts within the plant material that may directly induce methaemoglobinemia and Heinz body formation.

Timecourse

• Onset of signs is variable, although signs are usually apparent within 6-24 hours.
• Signs of hemolytic anemia or methaemoglobinemia may be delayed for 1-5 days.
• Full recovery may take 7 days or more.
• Dogs with the predisposing factors may develop severe signs within 24-48 hours.

Diagnosis

Treatment

Outcomes