Wild Onion (Allium spp.)
| Description | Distribution | Conditions of poisoning | Control | Toxic principle | Clinical signs | References
Wild onion (A. validum or A. canadense) is a bulbous herb of the Amaryllis family and is a close relative of cultivated onion (Allium cepa L.). It has a distinct onion odor. It has slender grass-like leaves and reaches about 2 feet in height when flowers appear in late summer. Leaves are narrow, long, and with parallel edges arising from the small underground bulb. Flowers, varying in color, depending on the species, from white to pink, appear at the top of a leafless stem and eventually become bulblets which drop to the ground and propagate.
It is thought that the name Chicago is derived from the smell of wild onions:
"Indians, mainly Potawatomi, who were the most powerful tribe around the south end of Lake Michigan, hunted, traded furs, and occasionally camped in the area they called "Checagou," evidently referring to the garlic wild onion smell which permeated the air."
Encyclopedia of Illinois, 2nd. Edition. Somerset Publishers, New York, 1994. p. 138.
Wild onion is found in meadows and woodlands in the northeastern and north central United States. Other species grow throughout the western United States. Several species of wild onion are found in Illinois with Allium canadense found in all counties.
Cattle are susceptible to onion poisoning and eating large amounts of this plant can cause death in this species. In areas where culled onions are grown commercially, they can be fed to cattle with few problems when the feed is mixed with ample amounts of other feed components. Poisoning may occur when cool spring weather delays growth of grass and wild onions are available in comparatively large amounts for cattle to graze. Horses and sheep are less susceptible, with goats being the least susceptible. In some cases, sheep may eat onions and show nothing more than slight hemoglobinemia.
Both wild and cultivated onions contain the same toxic principle, N-propyl disulfide which primarily affects erythrocytes. The principle effects are related to hemolysis (rupture of red blood cells). This is believed to be secondary to oxidant-associated effects, and Heinz bodies may sometimes be evident in red blood cells. Other compounds are believed to be responsible for the lacrimator (tear producing) and antithrombotic (anti-clotting) effects associated with onions and garlic. Various sulfur-containing metabolites are probably responsible for the odors associated with ingestion of onions and garlic.
Urine discoloration may vary from red wine to almost black. Muscle weakness, rapid breathing, and a rapid heart rate may be noted if hemolysis is sufficiently severe. Some animals may be icteric (jaundiced) and/or have a characteristic onion odor to the breath. Loss of weight and appetite may also occur. Although severe toxicoses may be lethal, doses may cause only taste and odor problems in the milk of dairy cows.
Allium entry in Wikipedia
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