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| Description. Kalmia
is a large shrub or small tree with smooth, elliptical, alternate or whorled
leaves. Showy white or pink flowers
with fused petals arise in the leaf axils of the upper stems. The plant has
green leaves all year in moderate climates and is primarily a threat to browsing
animals like sheep, goats and, less commonly, cattle and horses. |
| Geographic
range. Kalmia
grows wild in the woods and mountain foothills of the southeastern,
Appalachian and mid-Atlantic coastal states.
Some species are found in the Pacific coastal states and in temperate
areas along the Pacific Coast north to Alaska. |
| Toxic
principle.
Andromedotoxins
(grayanotoxins) are water-soluble diterpenoid compounds.
Leaves and flower nectar (including honey made from plant nectar) are
sources of the toxin. |
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Honey made from the plants has
been reported to cause cardiac arrhythmias, emesis, mild paralysis and
convulsions in humans and is known as “mad honey”. |
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| Toxicity. As little as 3 ml nectar/kg body weight
or 0.2% of the body weight as leaves may be toxic or lethal. |
| Mechanism
of toxicologic damage.
Andromedotoxins
bind to and modify the sodium channels of cell membranes, leading to prolonged
depolarization and excitation. Modification
of the sodium channels favors calcium movement into cells and results in a
positive inotropic effect similar to that of digitalis. |
Diagnosis
Clinical
signs. Salivation and a burning sensation in
the mouth are followed by emesis, diarrhea, muscular weakness and impaired
vision. Bradycardia, hypotension
(caused by vasodilation) and atrioventricular block are serious cardiovascular
effects that may be lethal. Dyspnea,
depression, and prostration develop, and death may occur within 1-2 days.
Ruminants often bloat. Aspiration
pneumonia can develop secondary to emesis.
Laboratory
diagnosis.
Generally non-specific
findings.
Lesions
are
non-specific. Detection of leaves in GI tract may assist in diagnosis.
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Treatment
ü
Detoxification.
Emesis is used where appropriate. Activated
charcoal should be administered repeatedly the first day.
ü
Supportive
therapy. Fluid replacement therapy
and respiratory support may be necessary. Atropine
is recommended for severe bradycardia. Isoproterenol
or sodium channel blockers (e.g., quinidine) may be used to treat heart block.
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