Taxus baccata (English yew). A member of the plant family TAXACEAE. Evergreen, dioecious tree or hedging shrub with small, narrow, dark green leaves. Male flowers in small cones, female flowers on separate branches, developing into bright red fruits, each with a single seed surrounded by a red fleshy cup or aril when ripe.


[affected.gif] Animals most affected
Cattle, horses, sheep, goats, (dogs, zoo animals, wild mammals).


[etiology.gif] Etiology
Ingestion of fresh or dried branches and leaves. (In the case of cattle, the palatability of the plant is noticeably increased when dried.) Poisoning with yew is common in animals.


[toxic.gif] Toxicity
Contains an alkaloid, taxine, and a heteroside, taxicatoside. Toxicity is maximal in winter and is not reduced by drying. Cut branches that are a few weeks old are more toxic than when fresh.

Oral doses in g fresh plant material per kg/ body weight:
LD cattle 1-10
  horses 0.5-2
  pigs 3
  sheep, goats 10-12
  dogs 8
 
rabbits  
 
20


[clinical.gif] Clinical features
Poisoning often violent and sudden in its onset (death within several minutes):

Acute poisoning, onset within several hours to several days (1-3), exhibited by:


[lesions.gif] Lesions
Non-specific:




[treatm~1.gif] Treatment
In most cases there is neither little time nor opportunity to treat the animal:



[labinv~1.gif] Laboratory investigations
Contents of the stomach or rumen (to identify fragments of plant material).


[case.gif] Case summaries
Due to extreme drought conditions, a herd of cows was moved into a pasture border by yew hedges. After the cows had been there for 8 hours, two of the animals were found to be dead. At autopsy, the only lesions identified by the veterinary surgery were cardiac petechiae, a congested liver and a haemorrhagic bladder mucosa. Laboratory analysis of the contents of the rumen identified yew leaves, confirming the cause of this poisoning.
Several horses were put out to graze in a new field. Two days later two of the animals were found to be dead. There were no toxic plants in the field, except for a single yew tree, which was out of reach of the horses. When the owner was questioned, it was learnt that the branches of the yew had been cut well back, but that the clippings had been left on the ground.
Yew does not lose its toxicity on cutting and drying; in fact its potency is increased by desiccation.