Ingestion of macadamia nuts by dogs has been associated with a nonfatal syndrome characterized by vomiting, ataxia, weakness, hyperthermia, and depression. Dogs are the only species in which signs have been reported.
Macadamia nuts are cultivated from Macadamia integrifolia in the continental US and M tetraphylla in Hawaii and Australia. The mechanism of toxicity is not known. Dogs have shown signs after ingesting 2.4 g of nuts/kg body weight. Dogs experimentally dosed with commercially prepared macadamia nuts at 20 g/kg developed clinical signs within 12 hours and were clinically normal without treatment within 48 hours.
Within 12 hours of ingestion, dogs with macadamia nut toxicosis typically develop weakness, depression, vomiting, ataxia, tremors, and/or hyperthermia. Tremors may be secondary to muscle weakness. Macadamia nuts may be identified in vomitus or feces. Mild, transient increases in serum triglyceride, lipase, and alkaline phosphatase concentrations were reported in some dogs experimentally dosed with macadamia nuts; these values quickly returned to baseline. Clinical signs generally resolve within 12–48 hours.
Diagnosis of macadamia nut toxicosis is based on history of exposure and clinical signs. Differential diagnoses include ethylene glycol toxicosis, ingestion of hypotensive agents, and infectious diseases (eg, viral enteritis).
For asymptomatic dogs with recent ingestion of more than 1–2 g/kg of macadamia nuts, emesis should be induced; activated charcoal may be of benefit after large ingestions. Most symptomatic dogs recover without any specific treatment. Severely affected patients may be administered supportive treatment such as intravenous fluids, antiemetics, analgesics, or antipyretics.