Plants that contain glycosides can be very harmful to pets. If your pet ingests any of the plants mentioned in these columns and is showing signs of illness, get him/her to your veterinarian post haste.
The most well known and classic of the cardiac glycoside plants is foxglove, Digitalis purpurea. We have known about the medicinal properties of this plant for centuries. Teas made from the plant were used as a diuretic and to slow the heart and the active ingredient digitalis is still an important drug used to treat heart failure. If ingested in large quantities, the plant can cause cardiac arrhythmias, vomiting, diarrhea, progressive weakness, cardiac failure and death.
The Oleander (Rose-Bay) also contains cardiac glycosides. When I practiced in Phoenix, AZ many backyards had Oleander bushes as hedges and I treated several horses for Oleander poisoning. Well-intentioned owners had mowed the lawn too close to the bushes mixing clippings from the Oleanders in with the grass clippings and fed everything to the horse (feeding grass clippings to horses is not a good idea under any circumstances). The Mock Azalea (Desert Rose, Desert Azalea, Sabi Star, Impala Lily, Kudu Lily) also contains cardiac glycosides.
Bufadienolides, another form of cardiac glycosides, are found in the Christmas Rose (Hellebore, Lenten Rose, Easter Rose) and the Mother-in-Law-Plant (Mother of Millions, Kalanchoe, Devils Backbone, Chandelier Plant). These plants are less toxic than those mentioned in the previous paragraph. Clinical signs include hypersalivation, abdominal pain, vomiting, diarrhea and, rarely, abnormal heart rhythm.
Cyanogenic glycosides (cyanide) are found in the stems, leaves and pits of Rosaceae plants. These include Apricots, Plums, Peaches, Cherries and cyanide is particularly high when the plants are in the process of wilting. Clinical signs include; brick red mucous membranes, dilated pupils, difficulty breathing, panting, shock and death. The Hortensia (Hydrangea, Hills of Snow, Seven Bark) plant and the Heavenly Bamboo (Sacred Bamboo, Nandina) also contain cyanogenic glycosides but rarely produce anything more than gastroenteritis if ingested.
The Common Privet (Privet, Amur, Wax-leaf) contains terpenoid glycosides that can result in gastroenteritis, incoordination and abnormally high heart rates but ingestion of this plant is rarely fatal. Clematis (Virgin’s Bower, Leatherflower) contains the irritant glycoside protoanemonin but ingestion only causes mild salivation, vomiting and diarrhea.
Various species of Milkweed (Ascieplas species) contain steroidal glycosidic cardenolides and are cardiotoxic, other species contain neurotoxins. Clinical signs following ingestions include vomiting, profound depression, weakness, anorexia (loss of appetite) and diarrhea. If large quantities are ingested these signs may be followed by seizures, dyspnea (difficult breathing) weak and rapid pulse, dilated pupils, kidney and/or liver failure, coma, respiratory paralysis and irreversible death.
Plants that contain volatile oils can cause contact dermatitis, vomiting, diarrhea, anorexia, and allergic reactions. Long term exposure can lead to bleeding tendencies. Chamomile (Manzanilla, Garden Chamomile, Roman Chamomile, True Chamomile, Corn Feverfew, Barnyard Daisy, Ground-Apple, Turkey-Weed) and Mayweed (Poison Daisy, Stinking Chamomile) contain the volatile oils; bisabolol and chamazulene as well as anthemic and tannic acids. The American Yew contains Taxine A & B and volatile oil. Ingestion of this plant can result in tremors, dyspnea, vomiting and sudden death from acute heart failure. Dogs poisoned by Yew are reported to have seizures.
Ricin is one of the most deadly toxins we know of. The Mole Bean Plant, Ricinus communis, is native to the tropics but is grown in North America as an ornamental or as a crop for castor oil. It is also known as the Castor Bean Plant, African Wonder Tree or the Castor Bean. Ricin inhibits protein synthesis and ingestion of as little as one ounce of the seeds of this plant can be lethal. Clinical signs usually develop 12 to 48 hours after ingestion of any portion of the plant and start with anorexia, excessive thirst, followed by weakness, abdominal pain, trembling, incoordination, dyspnea, progressive central nervous system depression and fever. As the toxicity progresses the animal can have bloody diarrhea, convulsions, coma and death.
The Cardboard Palm (Cycads and Zamias) contain Cycasin, related to ricin. Ingestion can result in vomiting, increased thirst, hemorrhagic gastroenteritis, coagulapathies resulting in bruising and other bleeding, liver damage followed by liver failure characterized by yellowing of the mucous membranes (icterus) and death. The Indian Rubber Plant (Fig, Weeping Fig) contains the proteolytic enzyme ficin and psoralen (ficusin) also related to ricin but mild toxicants. Skin contact can result in dermatitis while ingestion can cause oral irritation, excessive salivation and vomiting.