Locoweed

Locoweed (also crazyweed and loco) is a common name in North America for any plant that produces swainsonine, an alkaloid harmful to livestock.

Worldwide, swainsonine is produced by a small number of species, most of them in three genera of the flowering plant family Fabaceae: Oxytropis and Astragalus in North America,[1] and Swainsona in Australia.

Swainsonine, first isolated from Swainsona, was shown to be responsible for pea struck in 1979, and was reported in both Oxytropis and Astragalus in 1982.

[8] Although this was the first report of locoism in South America,[8] swainsonine had been isolated previously from A. pehuenches and several other species in Argentina and Peru.

Astragalus lusitanicus in Morocco was suspected,[11] but has been shown be neither a producer of swainsonine nor an accumulator of selenium.

Swainsonine has also been isolated from Sida carpinifolia and Ipomoea carnea, and both species have been reported to cause locoism.

[15] Embellisia, a fungus isolated from Oxytropis lambertii, has also been shown to produce swainsonine and to cause locoism in rats.

[16] Rhizoctonia leguminicola, a fungal plant pathogen that may occur on red clover (Trifolium pratense), also produces swainsonine.

Livestock that graze for several weeks on locoweed (and little else) develop a lysosomal storage disease similar to genetic mannosidosis.

[20] Diagnosis of clinical poisoning is generally made by documenting exposure, identifying the neurologic signs, and analyzing blood serum for alpha-mannosidase activity and swainsonine.

Keeping livestock away from locoweed-infested pasture in spring and fall when grass and other forbs are not actively growing is recommended.

[24][25] In horses, a small study has shown promising results using lithium chloride as the aversive agent.