Prickly comfrey
General poisoning notes:
Prickly comfrey (Symphytum
asperum) is a naturalized herb found in parts of southern Canada. The plant
contains pyrrolizidine alkaloids, which can cause veno-occlusive symptoms
leading to liver cirrhosis. The plant can also accumulate toxic amounts of
nitrates. Animals do not normally eat the plant because of the bristly hairs on
the leaves. However, swine given the plant as green fodder showed signs of
nitrate poisoning. Long-term use of the plant as food could lead to liver dysfunction
(Cooper and Huxtable 1984, Huxtable 1989).
Nomenclature:
Scientific Name: Symphytum asperum Lepech.
Vernacular
name(s): prickly comfrey
Scientific family
name: Boraginaceae
Vernacular family
name: borage
Geographic Information
British Columbia, Manitoba,
Nova Scotia, Ontario, Prince Edward Island, Quebec.
Toxic parts:
All parts, leaves,
roots, stems.
Notes on Toxic plant chemicals:
This plant
contains pyrrolizidine alkaloids such as echimidine. These alkaloids cause
veno-occlusive symptoms in animals. Total alkaloid content (as a percentage of
dry weight) for fresh leaves is about 0.01% and for dry leaves, about 0.059%.
Many members of the genus contain much higher concentrations of alkaloids in
the roots (Huxtable 1989).
Toxic plant chemicals:
Echimidine, nitrate.
Animals/Human Poisoning:
Note: When an
animal is listed without additional information, the literature (as of 1993)
contained no detailed explanation.
Swine
General symptoms of poisoning:
Breathing,
labored, cyanosis, methemoglobinemia.
Notes on poisoning:
Prickly comfrey is
not normally ingested by animals because of the bristly hairs on the leaves.
This plant can accumulate nitrates. In Britain, swine were poisoned when given
prickly comfrey as green fodder. Symptoms were typical for nitrate poisoning,
including apathy, labored breathing, cyanosis, and methemoglobinemia (Cooper
and Johnson 1984).
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