Foxglove
General poisoning notes:
Foxglove (Digitalis purpurea) is an attractive biennial plant that is cultivated in Canada and is naturalized in several provinces. Upon ingestion, this plant can cause toxic reactions that lead to severe sickness and death in animals and in humans. Several important pharmaceutical drugs such as digitalis and digoxin are derived from this plant. The chemicals increase the force of contraction of the heart muscle and are therefore used in cases of heart congestion. Foxglove (Digitalis purpurea) is a naturalized herb found in eastern Canada and British Columbia. It is also a common outdoor ornamental. All classes of livestock are susceptible to poisoning by foxglove. However, because of the unpalatable nature of the plant, poisoning is infrequent, although when it does occur it is often severe and dramatic, frequently resulting in death. Human poisoning occurs rarely. However, poisoning was reported in the children who ate the flowers or drank water from vases. Accidentally including foxglove leaves in tea has led to poisoning and death. Cardiac glycosides are commonly described drugs that have a low margin of safety. Slight overdoses of prescribed medicine can cause symptoms of toxicity (Cooper and Johnson 1984, Cheeke and Schull 1985, Joubert 1989).
Nomenclature:
Scientific Name: Digitalis purpurea L.
Vernacular name(s): foxglove
Scientific family name: Scrophulariaceae
Vernacular family name: figwort
Digitalis purpurea L.
Geographic Information
British Columbia, Newfoundland, Nova Scotia, Ontario.
Notes on Poisonous plant parts:
The entire plant contains toxic compounds. The leaves and seeds are used to produce digoxin and other cardenolides for pharmaceutical use. The chemicals do not lose their toxicity by drying, storage, boiling or incorporation in hay. The plants are unpalatable and are seldom eaten by animals (Cooper and Johnson 1984, Joubert 1989).
Toxic parts:
All parts, flowers, leaves, seeds, stems.
Notes on Toxic plant chemicals:
Digitoxin is one of several cardiac glycosides found in foxglove and is considered the most toxic of these chemicals. The toxins are split by hydrolysis into a sugar and an alglycone (nonsugar compound). The aglycones have a direct effect on the muscles to the heart (Joubert 1989).
Toxic plant chemicals:
digitoxin
Digitoxin
Chemical diagram(s) are courtesy of Ruth McDiarmid, Biochemistry Technician, Kamloops Range Station, Agriculture and Agri-Food Canada, Kamploops, British Columbia, Canada.
Animals/Human Poisoning:
Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.
Cats
Cattle
General symptoms of poisoning:
Death, dyspnea, lungs, congestion of.
Notes on poisoning:
Dairy cattle have become poisoned after ingesting foxglove. Postmortem examination showed consolidation of the apical lobes of both lungs, with marked emphysema and bullae formation in the diaphragmatic lobes. Duodenal and jejunal mucosa were extremely congested and hemorrhagic. Some cattle recovered after treatment, whereas others took several days. One cow died 2 days after ingesting foxglove (Thomas et al. 1987).
Dogs
Goats
Horses
Humans
General symptoms of poisoning:
Abdominal pains, diarrhea, nausea.
Notes on poisoning:
Digitalis poisoning toxicity has a variable latent period depending on the quantity ingested. Gross disturbances in heartbeat and pulse are common. Most cases of human poisoning result from slight overdoses of prescribed drugs that contain digoxin or other related chemicals. Smith et al. (1982) describe the symptoms of digoxin and digitoxin toxicity, including nausea and severe vomiting. Many people develop hyperkalemia. Advanced cardiac rhythm disturbances are common, along with tachycardia and ventricular fibrillation. Treating patients with purified Fab fragments of digoxin-specific antibodies produces an initial favorable response and should lead to safe, effective reversal of life-threatening digitalis intoxication. Accidental ingestion of foxglove has occurred when the leaves were used in tea or when flowers were ingested (Cooper and Johnson 1984).
Poultry
Sheep
Swine
General symptoms of poisoning:
Abdominal pains, convulsions, death, diarrhea.
Notes on poisoning:
General symptoms of foxglove poisoning for all types of animals include diarrhea, abdominal pain, irregular pulse, tremors, and convulsions. In severe cases, death occurs. Postmortem examination of pigs showed gastrointestinal inflammation, punctiform necrosis of the border of the spleen, and fatty degeneration of some nerve fibers in the heart. The presence of digitoxin in the body tissues confirms foxglove poisoning in animals (Cooper and Johnson 1984, Joubert 1989).
Turkeys
General symptoms of poisoning:
Appetite, loss of, convulsions, death, drowsiness, pupil dilation.
Notes on poisoning:
Several turkeys died after ingesting foxglove leaves. Several turkeys slowly recovered. The crops were surgically removed from affected birds, a procedure which speeded up recovery time (Parker 1951).
