Page 922 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

876 SECTION | XIV Poisonous Plants

VetBooks.ir potent compound with an i.v. LD 50 of 2 mg/kg and an ranges; not allowing animals to graze selectively;
unloading hungry animals in infested areas; lambing,
oral LD 50 of 130 mg/kg in mice (Welch et al., 2011b).
bedding, watering, or salting livestock in death camas-
Clinical signs of toxicosis are similar in all livestock poi-
soned by Zigadenus, irrespective of the species of plant infested areas; or placing animals on range where little
Zigacine involved. Excessive salivation is noted first, forage is available. Poisoning generally occurs in the
with foamy froth around the nose and muzzle that per- early spring when death camas is the first green forage
sists, followed by nausea and occasionally vomition in available and the young immature foliage is the most
ruminants (Panter et al., 1987). Intestinal peristalsis is toxic. Single losses of 300 500 sheep have been
dramatically increased, accompanied by frequent defeca- reported (Panter et al., 1987). In the 1987 case, 80% of
tion and urination. Muscular weakness with accompa- the dead sheep were 80- to 90-lb lambs. Three key fac-
nying ataxia, muscular fasciculations, prostration, and tors contributed to the losses: (1) ewes with lambs were
eventual death may follow. The pulse becomes rapid and driven through a heavily infested area of death camas
weak, and the respiration rate increases but the amplitude when the sheep were hungry; (2) the sheep were bedded
is reduced. Some animals become cyanotic, and the spas- down for the night near the death camas area, providing
modic struggling for breath may be confused with convul- immediate access to death camas the following morn-
sions. The heart fails before respiration, and at necropsy ing; and (3) the herder panicked and rapidly forced the
the heart is usually found in diastole. A comatose period sheep out of the area, contributing to the stress and
may range from a few hours to a few days before death. probably exacerbating the toxic effects and increasing
Pathological lesions are those of pulmonary conges- the losses.
tion. Gross lesions of sheep include severe pulmonary
congestion, hemorrhage, edema, and subcutaneous hemor-
rhage in the thoracic regions. Microscopic lesions include VERATRUM SPP.
severe pulmonary congestion with infiltration of red blood
cells in the alveolar spaces and edema. Diagnosis of poi- Veratrum belongs to the Liliaceae (Lily) family and is
soning may be established by clinical signs of toxicosis, composed of at least five species in North America.
evidence of death camas being grazed, histopathological During the mid-20th century, up to 25% of pregnant ewes
analysis of tissues from necropsied animals, and identifi- that grazed on pastures infested with Veratrum californi-
cation of death camas in the rumen or stomach contents cum in the mountains of central Idaho gave birth to lambs
(Panter et al., 1987). with serious craniofacial malformations. These malforma-
Similarity in clinical signs of toxicosis between certain tions ranged from the gross anomaly of cyclops to less
species of these plants suggests that the same alkaloids severe deformities of the upper and lower jaws. The
are present; however, differences in concentrations can Basque shepherds called the cyclopic defect “chatto,”
explain the differences in relative toxicity of different which translated as “monkey faced” lamb disease.
species (Table 61.11). Although losses from Veratrum have long been reduced
or eliminated on these ranges due to the application of
research findings and recommended management strate-
gies, biomedical research using the alkaloids, isolated and
Management and Prevention
identified at the Poisonous Plant Research Laboratory, as
Conditions conducive to poisoning by death camas molecular probes has opened a new frontier for human
include driving animals through death camas-infested medical research (James et al., 2004).

TABLE 61.11 Relative Toxicity in Sheep of Five Zigadenus spp.
Zigadenus Species Average Minimum Toxic Dose a Average Minimum Lethal Dose a
Z. gramineus 4 6
Z. paniculatus 10 25
Z. venenosus 4 20
Z. elegans 20 60
Z. nuttallii 2 5
a
Grams of green plant per kilogram body weight.