Generally prefer humid, moist environments with acidic soils.
Distribution
Frequently grown as an ornamental in USDA zone 4 - 8.
Animals Affected
Cattle, horses, sheep, llamas, birds
Yew
Toxic Principle
Yews contain a goup of highly toxic alkaloids. All parts of the plant green or dried except the fleshy part of the aril surrounding the seed are toxic. The highest concentration of alkaloid is generally found in the leaves in winter time. Adult cattle and horses have been fatally poisoned with as little as 8-16 ozs of yew leaves. Dried leaves are toxic.
Description
Yews are evergreen shrubs or small trees with glossy, rigid, dark green, linear leaves 1.5 - 2 inches long with pointed ends, and closely spaced on the branches. Inconspicuous axillary male and female flowers are produced on separate plants, forming showy red to yellow fruits (aril) containing a single seed.
Western yew (Taxus brevifolia nutt.) and American yew (Taxus canadensis, marsh) are two indigenous species. English yew (Taxus baccata) and Japanese yew (Taxus cuspidata) are commonly cultivated species in North America.
Gastrointestinal
Vomiting, diarrhea.
Musculoskeletal
Muscle trembling, incoordination.
Treatment
There is no effective treatment for yew poisoning. Supportive therapy should be implemented. Atropine sulfate is reportedly effective in counteracting the slow heart rate.
Cardiovascular system
Sudden death may be the only observed sign in many cases. A slow heart rate may be found with yew poisoning.
Respiratory System
Difficulty in breathing.
Nervous System
Nervousness, convulsions, and death.
Diagnosis
There are no characteristic lesions at necropsy. Diagnosis must be based on eliminating other causes of sudden death, evidence of accessibility of the animal to yew, and the presence of yew leaves in the rumen and stomach contents of the animal. Finely chewed leaves may have to be examined microscopically to positively identify the yew. Identification of taxine from chewed plant material and rumen contents using mass spectrometry also affords a precise means of confirming yew poisoning.
Special Notes
Yews should never be planted as hedges around animal enclosures, and prunnings from yews should never be made accessable to animals.
Yew
