Azalea and Rhododendron Poisoning
The beautiful flowering shrub adjacent to your porch may have a sinister side to it. Don’t let those colorful blooms fool you. Cuttings from these bushes may be toxic to your pets and livestock.
Azaleas and rhododendrons are members of the plant family Ericaceae, a group of garden shrubs that contain the toxin andromedotoxin which is a cardiac glycoside. Some rhododendrons will have an additional toxin called grayanotoxin in their pollen and nectar. Animals must consume these plants in rather large amounts, equivalent to 0.2% of their body weight for clinical signs of poisoning to develop. Livestock grazing near recently trimmed bushes are the most likely to show clinical signs of toxicosis. Even people have become ill from honey made by bees feeding on these plants.
Clinical signs typically develop within six hours following ingestion and reflect damage to the gastrointestinal tract and the heart. Livestock will be anorexic, salivate, be depressed, repeatedly swallow, and show general signs of nausea, projectile vomiting, ataxia, epiphora, paralysis of the limbs, stupor, bradycardia (slow heart rate) followed by tachycardia (rapid heart rate) later in the syndrome, heart block, coma, and death. In horses, the consumption of clippings will often lead to colic, tenesmus, and grinding of the teeth. Defecation may increase in frequency but seldom is diarrhea a prominent clinical sign. Animals surviving more than 2 days usually recover, but deaths have occurred as long as 14 days following ingestion.
When caught early, activated charcoal lavage may be used to prevent absorption followed by a saline cathartic to cause bowel evacuation. Additional treatment is symptomatic and is directed toward providing for the animal’s fluid needs and keeping their electrolytes balanced.
Fowler, Murray. Plant Poisoning in Small Companion Animals. Ralston Purina Co. 1981. P. 7.
Gupta, Ramesh Editor. Veterinary Toxicology. Elsevier. 2007. Pp. 197 and 201-202
Kahn, Cynthia. The Merck Veterinary Manual. Merck and Co. 2005. Pp. 2440-2441.
Smith, Bradford. Large Animal Internal Medicine. 2nd Edition. Mosby. 1996. P. 1881-1882.