Avocado leaves, bark, fruit and seeds are toxic to some animals. The active principle is believed to be persin but its mechanism of action has not been fully elucidated. Poisoning has been reported in birds (chickens, cockatiels, budgies, canaries, ostriches), horses, goats, sheep, mice and rabbits. A recent report described 14 rabbits that died within 30 hours of ingestion of avocado leaves (Aguirre et al. Acute heart failure in rabbits by avocado leaf poisoning. Toxicon. 2019;164:16-19).
Typically, avocado causes myocardial degeneration and heart failure, manifesting as generalised oedema and dyspnoea, raised creatine kinase, aspartate aminotransferase and lactate dehydrogenase. Elevated troponin has also been reported in horses. In lactating mammals there may also be mastitis and agalactia.
In cats and dogs, acute ingestion of avocado is usually not a concern, although it may cause gastrointestinal upset. The main risk is gastrointestinal obstruction from ingestion of the avocado seed (stone). Chronic ingestion is potentially hazard to dogs and presumably cats. Two dogs with a ‘fondness’ for avocado fruits died of congestive heart failure presumably after chronic ingestion (Buoro et al. 1994 Putative avocado toxicity in two dogs. Onderstepoort J Vet Res 61(1):107-9).
Management of avocado poisoning is supportive with anti-inflammatories, diuretics and antiarrhythmics.