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Distinguishing features
Western false hellebore is a native perennial herb 1-8 feet tall, with erect,
unbranched, very leafy
stems; the
leaves are broad, large, alternate and three-ranked, sheathing the stem, somewhat folded, strongly parallel veined. Flowers are in large panicles at top, white to greenish with the three sepals and three petals alike.
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| Description: Veratrum belong to
the Liliaceae family and are broad-leaved perennials that grow from thick,
fibrous rootstocks. They can attain
a height of 6 to 8 feet under optimal growing conditions.
The hairless leaves, which are often pleated, are alternate, clasping and
parallel-veined. Numerous flowers
are produced on branching terminal panicles or clusters.
The star-shaped flowers of V.
californicum are white in color; those of V.
viridae tend to be pale green. The
fruits are three-chambered capsules that contain numerous brown, winged, flat
seeds. |
| Geographic
Distribution:
~ fifty species of Veratrum are
distributed throughout Europe and NA. V. californicum and V. viridae
are the most significant species in NA. Both grow in mountainous areas where moist or swampy
conditions exist. V. californicum is usually restricted to altitudes above 5000 ft. in
the mountains of western NA. V.
viridae is more common in the eastern and southern regions of the continent.
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| Toxin: ~ 60 toxic steroidal alkaloids have been isolated from Veratrum
species. Many have potent
hypotensive properties. Three of
the alkaloids are teratogenic (jervine, cyclopamine and cycloposine). |
| Toxicity: 45 grams of root/rhizome given twice daily for three days to
ewes beginning on day 29 of gestation induced typical limb deformities in lambs. |
| MOTA:
the mechanism of teratogenesis is believed to be related to defective
chondrogenesis resulting from the inhibition of proteoglycan synthesis.
Defective cartilage formation effectively induces malformations of the head,
trachea and epiphyseal plates of the leg bones.
Alternatively, it has been proposed that the teratogenecity of
cyclopamine is related to its inhibitory effect on catecholamine release from
cholinergic receptors in the embyronic neuroepithelium thus disrupting normal
development. |
Diagnosis
Clinical signs:
manifestations of the teratogenic effects are directly related to the stage of
gestation at which the plant is eaten. If
pregnant ewes are exposed on the 14th day of gestation, lambs develop
classic cyclopian deformities (monkey-faced lambs).
Veratrum fed on the 17th and 18th days of
gestation induced motor-nerve paralysis of the hindlegs of lambs.
Other craniofacial deformities occur if Veratrum
is fed to ewes between the 12th and 30th days of gestation
(cleft palate, harelip and brachygnathia).
Lambs can develop shortened legs as a result of hypoplasia of the
metacarpal and metatarsal bones if ewes eat the plant between days 30 to 36.
Tracheal stenosis has also been reported in fetuses from ewes fed V.
californicum roots and rhizomes. Species
other than sheep can also be affected. Affected lambs are often stillborn. Adult sheep are seldom directly affected by Veratrum but can succumb to hypotensive effects if enough is
ingested. Dystocia can occur as a
result of oversized fetuses induced by prolonged gestation and lamb
malformations.
Laboratory: not useful
Lesions: typical fetal malformations
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| Treatment: not useful |
| Prevention: keeping
animals away from Veratrum sp. during
the first trimester of pregnancy has largely eliminated the problem in sheep.
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