This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
Other Common Names: White Sanicle, Indian Sanicle, Squawweed, Richweed, White Top, Deerwort-boneset.
There are few American plants whose poisonous properties have caused so much controversy as those of White Snakeroot. The disease called "trembles," which has lately been conclusively traced to it, was for many years a mystery. The trouble was formerly prevalent among animals feeding in wooded pastures, affecting more especially cattle and sheep, particularly in some of the eastern and central United States. It was variously attributed to bacteria, to a poison in the soil, to exhalations from the swamps, and to the bites of insects or small arthropods. Farmers learned that if they fenced their cattle away from the woods and swamps the disease did not trouble them. The serious character of the disease was increased by the fact that it was communicated to human beings by the milk of animals suffering from it. People who acquired it rarely recovered, and those who did survive were victims of permanent nervous debility. The fact of its communication by means of milk led to the application of the name "milksickness" to the disease.
The symptoms usually develop when cattle are out in pasture. Some stockmen believe that the disease is more prevalent in autumn. This may be due partly to the fact that unusual exercise and excitement hasten the development and increase the intensity of the symptoms, so that the disease becomes more apparent at the time when stock is being driven to market. The scarcity of other pasture at this season would also lead to the ingestion of larger amounts of the plant. In rare cases animals are attacked in winter, when, according to experienced stockmen, the disease comes as a result of the feeding of swamp hay. This fact is significant, as such hay is the only winter feed likely to contain White Snakeroot.
Trembles or Milksickness
Fig. 18. - White Snakeroot - Eupatorium urticaefolium.
Wolf, Curtis and Kaupp of the North Carolina Agricultural Experiment Station, have recently published an extensive account of their researches on "trembles," in a special bulletin. From the results of feeding experiments they traced the disease to the White Snakeroot. Their treatise gives a complete and valuable account of the symptoms as observed by themselves and by others.
Cattle exhibit listlessness, stiffness of joints and sluggishness with weakness and trembling, especially when driven. There is constipation and a foul "garlicky" breath. It is noted that among a group of animals, some may escape harm while others contract the disease, though all have eaten the plant apparently to the same extent. In sheep, in addition to the above symptoms, the following are noted: loss of appetite, gritting of the teeth, quick, laboured breathing, marked ataxia, frequent and scanty urination. The trembling is very pronounced and accompanied by tetanic spasms.
In pigs the appetite is not impaired until the later stages but the trembling is very violent.
In man there is abdominal pain, vomiting, and excessive thirst; otherwise the symptoms resemble those in the lower animals.
No satisfactory cure for the disease has been discovered and the chances for such a discovery are not hopeful, as the poison produces fundamental changes in the internal organs. The only way of overcoming the disease, therefore, is by not allowing the animals access to the Snakeroot. Pasture areas infested by it should be fenced off or cleared of trees and broken up by the plow
The plant is a native perennial, growing from New Brunswick to Ontario and south of the line, in damp woods, especially on their borders and in land recently cleared but not broken up. Its slender branching stem is one and one-half to three and one-half feet high, with opposite long-petioled leaves, broadly ovate and with coarse, sharp teeth. There is a characteristic mat of dark brown fibrous roots. The small flower heads, one-quarter of an inch or less in diameter, are white, and arranged in close compound clusters.