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United States Department of Agriculture

Agricultural Research Service

Title: The Comparative Pathology of Locoweed Poisoning in Livestock, Wildlife and Rodents

Authors
item Stegelmeier, Bryan
item Lee, Stephen
item James, Lynn
item Gardner, Dale
item Panter, Kip
item Ralphs, Michael
item Pfister, James

Submitted to: Poisonous Plant Global Research and Solutions
Publication Type: Book / Chapter
Publication Acceptance Date: May 31, 2006
Publication Date: June 20, 2007
Citation: Stegelmeier, B.L., Lee, S.T., James, L.F., Gardner, D.R., Panter, K.E., Ralphs, M.H., Pfister, J.A. 2007. The comparative pathology of locoweed poisoning in livestock, wildlife and rodents. Poisonous Plant Global Research and Solutions. Chpt. 61, pp. 359 - 365.

Interpretive Summary: Locoweeds are Astragalus and Oxytropis plants that contain a toxin called swainsonine. Swainsonine inhibits lysosomal a-mannosidase and Golgi mannosidase II causing a storage disease similar to mannosidosis. All animal species are susceptible to locoweed poisoning; however, there are remarkable variations in locoweed-induced clinical signs and lesions. Unlike livestock species that have dull hair coat, neurologic disease, decreased libido, infertility, abortion, cardiovascular disease and death, seemingly resistant rodents and mule deer only develop subtle neurologic signs and wasting. The characteristic microscopic lesions in livestock have been described as vacuolation of brain cells and many other cells throughout the body. Tissues most severely affected include thyroid follicular epithelium, exocrine pancreas, renal tubular epithelium, testes, ovaries, and macrophages/monocytes in nearly all tissues. Horses are highly susceptible to poisoning as they develop clinical signs and neurologic lesions at relatively low doses of short duration. In comparison rodents and mule deer are relatively resistant to poisoning. These species develop similar neurologic lesions as horses, but only at much higher doses and longer durations. Different organ systems are also affected. Rodents and mule deer develop extensive pancreatic and intestinal lesions with little change in other tissues. Recent isolation of mannosidases with different swainsonine binding affinities suggests that differences in severity, distribution and progression of locoweed induced lesions are probably due to tissue and species specific mannosidase expression.

Technical Abstract: Locoweeds are Astragalus and Oxytropis plants that contain an indolizidine alkaloid swainsonine, a potent inhibitor of lysosomal a-mannosidase and Golgi mannosidase II. All animal species are susceptible to locoweed poisoning; however, there are remarkable variations in locoweed-induced clinical signs, lesion distribution and the extent of histologic lesions. Unlike livestock species that have dull hair coat, neurologic disease, decreased libido, infertility, abortion, cardiovascular disease and death, seemingly resistant rodents and mule deer develop subtle neurologic signs and wasting. The characteristic microscopic lesions in livestock have been described as neuro-visceral cellular vacuolation with axonal dystrophy and foamy vacuolation of monocytes and macrophages in many tissues. Lysosomal enlargement seen as vacuolation is also seen in various non-neuronal tissues including thyroid follicular epithelium, exocrine pancreas, renal tubular epithelium, testes, ovaries, and macrophages/monocytes in nearly all tissues. Horses are highly susceptible to poisoning as they develop clinical signs and neurologic lesions at relatively low doses of short duration. In comparison rodents and mule deer are relatively resistant to poisoning. These species develop similar neurologic lesions as horses, but only at much higher doses and longer durations. Different organ systems are also affected. Rodents and mule deer develop extensive pancreatic and intestinal lesions with little change in other tissues. Recent isolation of mannosidases with different swainsonine binding affinities suggests that differences in severity, distribution and progression of locoweed induced lesions are probably due to tissue and species specific mannosidase expression.

Last Modified: 12/21/2014
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