Ageratina altissima is toxic to horses. The reported severity is critical. Also known as White Snakeroot, White Snakeroot and Appalachian White Snakeroot.
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Weak Pulse High Heart Rate Dilated Pupils Dry Mouth Incoordination Diarrhea Vomiting Seizures Coma Abdominal Pain Drooling Dermatitis Difficulty Breathing Cardiac Failure Weakness Stiffness Tremors Cardiovascular Collapse Difficulty Swallowing Liver Failure
The color of each symptom follows the severity scale above.
Ageratina altissima, also known as white snakeroot, richweed, or white sanicle, is a poisonous perennial herb in the family Asteraceae, native to eastern and central North America. An older binomial name for this species is Eupatorium rugosum, but the genus Eupatorium has undergone taxonomic revision by botanists, and some species once included in it have been moved to other genera.
White snakeroot contains the toxin tremetol; when the plants are consumed by cattle, the meat and milk become contaminated with the toxin. When milk or meat containing the toxin is consumed, the poison is passed on to humans. If consumed in large enough quantities, it can cause tremetol poisoning in humans. The poisoning is also called milk sickness, as humans often ingested the toxin by drinking the milk of cows that had eaten snakeroot. Although 80% of the plant's toxin, tremetone, decreases after being dried and stored away for 5 years, its toxic properties remain the same.
During the early 19th century, when large numbers of European Americans from the East, who were unfamiliar with snakeroot, began settling in the plant's habitat of the Midwest and Upper South, many thousands were killed by milk sickness. Notably, milk sickness was possibly the cause of death in 1818 of Nancy Hanks Lincoln, mother of Abraham Lincoln. It was some decades before European Americans traced the cause to snakeroot, although today Dr. Anna Pierce Hobbs Bixby is credited with identifying the plant in the 1830s. Legend has it that she was taught about the plant's properties by a Shawnee woman. In addition to cattle, the plants are also poisonous to horses, goats, and sheep. Signs of poisoning in these animals include depression and lethargy, placement of hind feet close together (horses, goats, cattle) or held far apart (sheep), nasal discharge, excessive salivation, arched body posture, and rapid or difficult breathing.
Also recorded as Richweed and Snakeroot.
More from the Asteraceae family:
Countries with the most wild observations, from GBIF data.