White Snakeroot

Ageratina altissima (syn. Eupatorium rugosum, Eupatorium urticaefolium) also known as White Sanicle, Tall Boneset, Fall poison, Richweed and most commonly White Snakeroot is a flowering herbaceous perennial with a long history of poisoning man as well as animals. Blooming in mid to late summer or fall, snakeroot is adaptive to different growing conditions and can be found growing wild in woods and brush thickets, in low, moist areas or bordering streams from southeastern Canada, west as far as North Dakota, south to central Georgia, and west to Texas. White snakeroot grows from a shallow mat of fibrous roots, forming stiff stems 3 to 4 ½ feet tall. The flowers are a clean white color and after blooming, small seeds with fluffy white tails are released to blow in the wind. The leaves are opposite, long petioled, egg to heart-shaped, and range from 3 to 6 inches in length with coarsely and sharply serrate leaf margins and a sharply pointed tip.

The primary toxin Tremetone (tremetol) is found in all parts of the plant with the highest concentrations being found in the leaves and stems. There is some debate between sources in regards to the toxicity of the green plant versus the dry plant. Some authorities assert that toxicity decreases with drying, while others state that it remains just as toxic when dried. Regardless, no sources state that toxicity is eliminated with drying, as such it could pose a health hazard to domestic animals when dried in hay. Additionally tremetone acts in a cumulative fashion so small amounts eaten over a prolonged period of time could result in the overall concentration of the toxin reaching life threatening or lethal levels in the body. All animals including man are susceptible to poisoning. The toxin is readily secreted in to the milk of lactating animals that have ingested the plant. In the past entire villages and towns were nearly wiped out when humans drank contaminated milk from cows; a condition known as “milk sickness”.

In animals poisoned by snakeroot, the condition is referred to as “trembles” due to the muscle tremors that nearly always manifest as a symptom of severe intoxication. The amount that needs to be ingested in order to suffer potentially life threatening consequences is relatively small, around 0.5 to 1.5% of its total body weight in green plant material. The amount of dry material an animal would need to ingest (as would be found as a contaminate in hay) may be significantly more, but it is important to remember the effects of the toxin are cumulative so long term ingestion of small amounts could still result in death. In horses experimentally poisoned with white snakeroot, poisoning was induced in 1 to 2 weeks after ingesting 1- 2 percent of their body in green plant material. Roughly 20 lbs of green plant material consumed over the course of several days will severely intoxicate horses and most cattle. Calves and foals are susceptible to snakeroot poisoning when they nurse from mothers that have been eating the plant. Due to the cumulative nature of the toxin, the onset of symptoms may vary from a couple of days to as long as a few weeks.

In animals, the initial symptoms of intoxication are loss of energy, lazy, sluggish, or lethargic behavior and a marked aversion to moving around. Cattle, commonly develop muscle tremors, colic like symptoms, constipation, bloody feces (blood may be dark and tarry, or appear as streaks or clots) with or without mucus and the distinct smell of acetone on the breath due to ketosis in severely poisoned animals. Progression can be quite rapid once the trembles begin, animals typically become reluctant to move, show obvious stiffness and eventually lie down unable to rise. In horses, paralysis of the pharyngeal muscles may lead to signs of choking. Myoglbinurea caused by rhabdomyolysis may cause the urine to become dark brown. This is generally followed by cardiac abnormalities, eventually culminating in congestive heart failure, cardiac arrest and death. Death may occur from 1 day to 3 weeks after the symptoms appear.