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Toxicoses in Livestock from the Hemlocks (Conium and Cicuta Spp.)¹

U.S. Department of Agriculture², Logan, UT 84321

Abstract

The hemlocks, Conium maculatum (poison-hemlock) and Cicuta spp. (waterhemlock), are poisonous plants that cause sizeable losses to the livestock industry. Clinical signs of poisonhemlock toxicosis are similar in all species of livestock and include muscular weakness, incoordination, trembling, initial central nervous sytem stimulation, depression and death from respiratory paralysis. Poison-hemlock also causes skeletal defects in the offspring of cattle, pigs and sheep and cleft palate in pigs when ingested during specific periods of gestation. The primary toxicants in poison-hemlock are coniine and -coniceine. Coniine predominates in mature plants and seed, whereas -coniceine predominates in early growth of the plant. Waterhemlock is the most violently toxic poisonous plant known. The toxicant is cicutoxin, which acts on the central nervous system, causing violent convulsions and death. Clinical signs of poisoning appear within 15 min after ingestion of a lethal dose and include excessive salivation, nervousness, tremors, muscular weakness and convulsive seizures interspersed by intermittent periods of relaxation and a final paralytic seizure resulting in anoxia and death. Elevated activities of lactic dehydrogenase, aspartate aminotransferase and creatine kinase in blood are observed, indicative of muscular damage. Toxicoses from poisonhemlock and waterhemlock generally occur in early spring when both plants emerge before other, more palatable plants begin to grow. All parts of the poison-hemlock plant are toxic. The root or tubers of waterhemlock are toxic; however, experimental evidence concerning the toxicity of other plant parts is inconclusive.

¹ Presented as an invited paper in a symposium on Poisonous Plants and Animal Toxicoses at the 79th Annu. Mtg. of ASAS, Utah State Univ., Logan, UT., July 31, 1987.

² ARS, Poisonous Plant Res. Lab., 1150 East 1400 North, Logan, UT 84321.