Poison-hemlock-Conium maculatum L.-Poisonous plant

Poison-hemlock

General poisoning notes:

Poison-hemlock (Conium maculatum) is a naturalized herb found in parts of southern Canada. The plant grows on dry to moist soils. Cattle, goats, horses, swine, and sheep as well as rabbits, poultry, deer, and humans have been poisoned after ingesting poison-hemlock. Animal species vary in their susceptibility to acute toxicity (Keeler et al. 1980):

cows	3.3 mg/kg body weight	1.5-2 h
ewes	44 mg/kg body weight	1.5-2 h
mares	15.5 mg/kg body weight	30-40 min

Poison-hemlock causes toxicity and death in animals after it is ingested. It also causes teratogenic effects called crooked calf disease in young pigs and cattle, caused by the chemical coniine (Keeler 1974, Panter et al. 1985).

Nomenclature:

Scientific Name: Conium maculatum L.

Vernacular name(s): poison-hemlock

Scientific family name: Apiaceae

Vernacular family name: parsley

Geographic Information

British Columbia, Nova Scotia, Ontario, Quebec, Saskatchewan.

Notes on Poisonous plant parts:

All parts of poison-hemlock contain some level of the alkaloids, except for the sap in young plants. The most toxic chemical, gamma-coniceine is abundant in leaves flowers and less common in the fruits, where it is quickly converted to coniine and N-methylconiine (Cromwell 1956).

Toxic parts:

Flowers, leaves, mature fruit, roots, seeds, stems, young shoots.

Notes on Toxic plant chemicals:

gamma-Coniceine is the precursor of the other alkaloids in poison- hemlock. This chemical is a partly unsaturated piperidine alkaloid. The other chemicals, including coniine and N-methylconiine, are saturated. During the first year of growth, gamma-coniceine is the predominant chemical. During the second year of growth, the content of both coniine and N-methyconiine increase, especially in the leaves and fruits, with a decrease in the first chemical. gamma-Coniceine is considered seven or eight times more toxic than coniine, with N-methyconiine even less toxic (Cromwell 1956, Fairbairn and Suwal 1961, Panter and Keeler 1989).

The following LD₅₀ toxicities in mice have been reported (Bowman and Snaghvi 1963):

gamma-coniceine	death time
2.6 mg/kg (intravenous)	30 sec
12.0 mg/kg (subcutaneous)	12 min
12.0 mg/kg (oral)	8 min

coniine	death time
19.0 mg/kg (intravenous)	30 sec
80 mg/kg (subcutaneous)	15 min
100 mg/kg (oral)	10 min
N-methylconiine		death time
27.5 mg/kg (intravenous)		30 sec
150.5 mg/kg (subcutaneous)		16 min
204.5 mg/kg (oral)		12 min

Toxic plant chemicals:

Coniine, gamma-coniceine, N-methylconiine.

Coniine

Animals/Human Poisoning:

Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.

Cattle

General symptoms of poisoning:

arthrogryposis

breathing, rapid

carpal joint, flexure

depression

diarrhea

elbow joint, flexure

gait, unsteady

incoordination

limbs,lateral rotation

muscle spasms

salivation

scoliosis

teeth grinding

torticollis

trembling

urine, coffee-colored

vomiting

Notes on poisoning:

General signs of poisoning in all types of livestock include apathy, salivation, frequent regurgitation, teeth grinding, and reduced milk production. For a lethal dose, cattle require coniine at a rate of about 16 mg/kg of body weight (Keeler et al. 1980).

Horses

General symptoms of poisoning:

collapse

trembling

unconsciousness

Notes on poisoning:

Horses exhibit symptoms similar to other types of livestock that have ingested poison-hemlock. Trembling and paralysis are common symptoms.

Humans

General symptoms of poisoning:

coma

convulsions

death by asphyxiation

dizziness

headache

incoordination

pupil dilation

thirsty

vomiting

Notes on poisoning:

Poison-hemlock has been ingested on purpose and accidentally. Socrates was executed in 399 B.C. by an extract of this plant. Humans have accidentally ingested it, mistaking it for carrot or parsnip. The symptoms are similar to those in other animals. Coldness is often felt in the extremities. There is rapid onset of irritation of mucous membranes of the mouth and throat, accompanied by salivation and nausea. Severe poisoning may cause coma and death by respiratory failure. Treatment includes administering activated charcoal after emesis ceases. Treatment is otherwise symptomatic. Despite the severity of poisoning mortality is low (Cooper and Johnson 1984, Lampe and McCann 1985).

Rabbits

General symptoms of poisoning:

ataxia

breathing, shallow

death

trembling

weakness

Sheep

General symptoms of poisoning:

ataxia

carpal joint, flexure

death

defecation, frequent

salivation

tail, kinked

trembling

urination, frequent

weakness

Swine

General symptoms of poisoning:

arthrogryposis

articular rigidity

ataxia

blindness

blindness, temporary

breathing, labored

breathing, rapid

carpal joint, flexure

collapse

death

death by asphyxiation

fetlock joint, flexure

gait, staggering

gait, unsteady

heart rate, elevated

lacrimation, severe

palatoschisis

paralysis

prostration

pupil dilation

scoliosis

syndactylism

temperature, elevated

trembling

urination, frequent

vision, impaired

weakness

Turkeys

General symptoms of poisoning:

death

diarrhea

enteritis

kidney, congestion of

liver, congestion of

lungs, congestion of

paralysis

salivation

weakness