22. WHITE SNAKEROOT, WHITE SANICLE, RICHWEED

Eupatorium rugosum

(daisy family)

TOXICITY RATING: High. White snakeroot will be eaten, especially in the late summer and fall, and is often lethal.

ANIMALS AFFECTED: Cattle, horse, goat, sheep, swine. All grazing animals can be affected by white snakeroot, and the toxin passes in the milk, so nursing animals and humans are also at risk.

DANGEROUS PARTS OF PLANT: Leaves and stems, possibly flowers. Roots seem to have a lower toxicity.

CLASS OF SIGNS: Trembling, sweating, depression, stiff gait, heart failure, jaundice, toxic milk, death (may be sudden).

PLANT DESCRIPTION: White snakeroot (fig. 22) grows from fibrous, matted roots as a smooth, erect, perennial herb 1 to 3 feet high with opposite, oval, pointed-tipped leaves with sharply-toothed edges. The upper surfaces of the leaves are dull, the lower surfaces shiny with three prominent main veins. Small white flowers in compound terminal clusters are conspicuous in late summer. White snakeroot is found in woods, damp and shady pastures, and occasionally in thickets and clearings (especially at the edges of wooded areas) in all 92 Indiana counties.

SIGNS: Clinical signs include: depression, stiff gait, periods of sweating, normal or subnormal body temperature, labored or shallow respiration, muscle tremors, trembling, partial throat paralysis, jaundice, passage of hard feces, prostration, death (death may be sudden with no prior signs). Onset of signs is typically 2 days to 3 weeks. Death occurs within 1 day to 3 weeks, with horses typically succumbing in 1 to 3 days. Even if the horse does not die from this toxin, it may suffer permanent heart damage and be unsuitable for work or pleasure purposes. The toxic component is tremetol, and the toxic dose of the green plant is approximately 1% to 10% of the body weight of the animal at one time or over several doses. The toxin is cumulative, so one large dose or multiple smaller doses over time can kill. The toxin is excreted in the milk, so lactating animals are slower to show signs of toxicity, but the nursing animals will then be affected by the toxin. Humans who drink raw milk from affected animals can also be poisoned, sometimes fatally (the disorder was called "milk sickness" in colonial times).

The primary danger occurs in late summer throughout the fall, especially in overgrazed pastures or where there is insufficient food. Poisonings in early winter where the animals eat stalks that extend above the snow have also been reported. The edges of woods or thickets are common locations for white snakeroot. Dry years are also associated with more reports of toxicity, perhaps due to inadequate pasture forage.

FIRST AID: Supportive care is required, since there is no specific antidote. Many affected animals will die or be permanently disabled. Remove all animals from the pasture or fence off the wooded areas, especially in the fall through winter. Continue to milk lactating animals, and discard milk. A veterinarian will be able to provide supportive care to animals showing signs, but death is likely once clinical signs develop.

SAFETY IN FEEDS: Drying decreases but does not eliminate the toxin, therefore hay with white snakeroot in it is unsafe for consumption.

PREVENTION: Learn to recognize and avoid white snakeroot. Do not allow animals to graze this plant under any circumstance. To do this, fence off wooded areas, provide supplemental feed (especially in the late fall and winter), or treat the snakeroot with herbicides. Be cautioned that treatment with herbicides may make the plant more palatable, so allow several weeks to pass between spraying and allowing animal access (be sure the plants are completely dead). The problem may recur the following year, so plan ahead to avoid animal loss. Under no circumstances should raw milk from affected animals be used for animal or human consumption.