English yew
General poisoning notes:
English yew (Taxus baccata) is an introduced ornamental shrub that is hardy in the warmest parts of Canada. This shrub has caused poisoning and death in cattle, horses, and humans. Ingesting leaves, bark, or seeds can cause poisoning in all animals. The fleshy fruit pulp is considered to be nontoxic (or low in toxicity). Taxine, a complex of alkaloids, is found in the plant. Children should be taught not to eat the fruit or seeds of this plant. Animals should not have access to the shrub or clippings of the branches (Cooper and Johnson 1984, Feldman et al. 1987).
Nomenclature:
Scientific Name: Taxus baccata L.
Taxus baccata L.
Notes on Poisonous plant parts:
All parts of the plant contain significant amounts of the alkaloids, with the exception of the fleshy part of the fruits, which is regarded as nontoxic or low in toxicity. The seeds are toxic. Ingesting the entire fruits without removing the seeds can cause poisoning. Toxicity is not reduced with drying. Hedge clippings from these plants are as toxic as fresh plants (Cooper and Johnson 1984).
Toxic parts:
Leaves, pollen, seeds.
Notes on Toxic plant chemicals:
Taxine (taxin) is a complex mixture of alkaloids that is rapidly absorbed from the digestive tract and interferes with heart action. Case studies on humans have shown that the alkaloids are strongly diuretic and cause severe ventricular rhythms (Feldman et al. 1987). Smith (1989) discusses a technique to diagnose taxine quickly, using direct insertion probe mass spectrometry from the rumen. The lethal dose was estimated at 1-10 g/kg of body weight for ruminants and 0.5-2 g/kg for horses (Cooper and Johnson 1984).
Toxic plant chemicals:
Taxine.
Animals/Human Poisoning:
Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.
Cattle
General symptoms of poisoning:
Agitation, collapse, convulsions, death, gait, staggering, incoordination, pupil dilation, trembling.
Notes on poisoning:
In Europe, cattle have been poisoned after ingesting English yew. Symptoms include muscular trembling, coldness, a rapid and then weak pulse, and groaning. In some cases, symptoms are not evident until sudden collapse or death. Death does not always occur and spontaneous recovery has been reported. Postmortem findings may only show yew plant material in the stomach. Inflammation of the stomach and intestines may occur (Cooper and Johnson 1984).
Horses
General symptoms of poisoning:
Abdominal pains, collapse, confusion, death, gait, staggering, incoordination.
Notes on poisoning:
Horses have symptoms similar to cattle after ingesting plant material of English yew. In one experiment, a pony given a strained aqueous extract from yew twigs and berries, by stomach tube, developed signs after 1 h and died 15 min later. Ingestion results in the following symptoms: coldness, a rapid and then weak pulse, excitability, and collapse, followed by death (Cooper and Johnson 1984).
References:
Cooper, M. R., Johnson, A. W. 1984. Poisonous plants in Britain and their effects on animals and man. Her Majesty's Stationery Office, London, England. 305 pp.
