Details

Common Name
Water Hemlock, spotted water Hemlock
Botanic Name
Cicuta douglasii (DC.) J.M. Coult. & Rose,
Plant Family
Apiaceae
Habitat
Prefers wet marshy sites in meadows, along strems, irrigation ditches, often growing with its roots in water.
Animals Affected
Cattle, horses, sheep, humans
Water-hemlock
Toxic Principle
Cicutoxin, cicutol, cicudiol, and isocicutoxin are potent unsaturated alcohols found in all parts of the plant. The roots are highly poisonous at all times, and livestock consuming as little as 2 ounces of the root, will usually die. The toxin is rapidly absorbed from mucous membranes and the digestive tract. The toxin acts primarily on the brain acting at GABA-A receptors and affecting the inhibitory neurons causing violent convulsions and respiratory failure.
Description
At least 4 major species of water hemlock occur in North America. They are stout, erect, hairless perennials growing to a height of 4-6 feet. Stems arise from a cluster of tuberous roots. The stems are hollow and compartmentalized, the partitions are compressed towards the root base. A yellow, turnip-smelling fluid oozes from the cut surface that contains the toxin. The leaves are alternate, 1-3 times pinnate with toothed edges, and leaf veins that run to the leaf notches. The flowers are showy, white loose umbels. The fruits are oval, flattened laterally with prominent ribs. All species of Cicuta should be considered highly toxic. Similar toxins are found in the Oenanthe species (water dropworts). Cicuta maculata is found predominantly in the eastern United States, while C. douglasii occurs more commonly in the western States. Cicuta maculata, also known as spotted water hemlock, poison parsnip, spotted cowbane ,or spotted parsley has red stems.
Gastrointestinal
Excessive salivation, vigorous chewing movements, and teeth grinding
Musculoskeletal
Animals that experience severe convulsions from the water hemlock develop muscle degeneration.
Treatment
Intravenous administration of either a single 10mg/kg or 1 mg/kg dose of diazepam (repeated as needed), immediately controlled convulsions and prevented death in goats poisoned with C. maculata (1). Intravenous administration of sodium pentobarbital (20mg/kg) with 75 mg atropine (intramuscular) at the onset of seizures prevented lethal cardiac and skeletal muscle degeneration and death in ewes (2). Direct comparison of these 2 treatments indicated better responses to diazepam. Laxatives may be beneficial by helping to remove the plant from the digestive system. Vomiting should be induced in dogs and people suspected of eating water hemlock. Artificial respiration should be given where possible if respiratory failure occurs. The use of dilute acetic acid orally in cattle has been reported beneficial in neutralizing the toxin. 1. Green BT, Stonecipher CA, Welch KD, Lee ST, Cook D. Evaluation of diazepam as a drug treatment for water hemlock (Cicuta species) poisoning in Spanish goats. Toxicon. 2022 Jan 15;205:79-83. doi: 10.1016/j.toxicon.2021.12.003. Epub 2021 Dec 3. PMID: 34871669. 2. Panter KE, Baker DC, Kechele PO. Water hemlock (Cicuta douglasii) toxicoses in sheep: pathologic description and prevention of lesions and death. J Vet Diagn Invest. 1996 Oct;8(4):474-80. doi: 10.1177/104063879600800413. PMID: 8953535.
Cardiovascular system
Heart muscle degeneration develops in animals that experience convulsions. The more severe the convulsions the worse the heart degeneration, and the poorer the prognosis
Respiratory System
Death from respiratory paralysis.
Nervous System
Cicutoxin is a potent neurotoxin causing rapid onset of muscle tremors and violent convulsions. Death often occurs in a matter of 2-3 hours after the onset of clinical signs. Convulsive seizures and lateral recumbency precede death.
Ocular System
Dilated pupils
Diagnosis
Sudden death, and finding of water hemlock parts in the rumen and stomach.
Special Notes
Fatalities have occurred in children who have sucked on the hollow stems of water hemlock. Fatalities occur when people mistakenly eat the tuberous roots of water hemlock for the edible root of common yampa (Perideridia gairdneri). The tuberous roots have also been mistaken for edible wild parsnip (Pastinaca sativa). The plant should be dug up and burned where possible. Spraying water hemlock with 2,4,-D herbicide will kill the plant, but it should be remembered that the herbicide may make the plant more palatable before it dies off.
Water hemlock stem sectioned to show
Water hemlock tuberous roots