Editing Locoweed

{{Short description|Plant that produces swainsonine}}
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{{Use mdy dates|date=March 2024}}
'''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 [[Genus|genera]] of the [[Angiosperm|flowering plant]] family [[Fabaceae]]: ''[[Oxytropis]]'' and ''[[Astragalus (plant)|Astragalus]]'' in [[North America]],<ref name="RalphsJames1999"/> and ''[[Swainsona]]'' in [[Australia]]. The term locoweed usually refers only to the North American species of ''Oxytropis'' and ''Astragalus'', but this article includes the other species as well. Some references may incorrectly list ''[[Datura]]'' as locoweed.<ref>{{Cite web|url=https://www.flickr.com/photos/alanenglish/417160351/|title = Sacred Datura (Locoweed) on North Kaibab Trail Grand Canyon - don't even think about smokin' this s**t uff|date = October 19, 2006}}</ref>

Locoweed is relatively [[palatable]] to livestock, and some individual animals will seek it out. Livestock poisoned by chronic ingestion of large amounts of swainsonine develop a medical condition known as ''locoism'' (swainsonine disease, swainsonine toxicosis in North America) and ''pea struck'' in Australia.<ref name="pmid2110378">{{cite journal |vauthors=Pritchard DH, Huxtable CR, Dorling PR | title = Swainsonine toxicosis suppresses appetite and retards growth in weanling rats | journal = Research in Veterinary Science | volume = 48 | issue = 2 | pages = 228–30 |date=March 1990 | pmid = 2110378 | doi = 10.1016/S0034-5288(18)30995-0}}</ref> Locoism is reported most often in cattle, sheep, and horses, but has also been reported in [[elk]] and [[deer]]. It is the most widespread poisonous plant problem in the western [[United States]].<ref name="RalphsJames1999"/><ref>{{Cite web|url=http://www.ars.usda.gov/is/pr/2010/100621.htm|title=ARS and New Mexico Scientists Take a Long Look at Livestock and Locoweed : USDA ARS}}</ref>

Most of the 2,000 species of ''Astragalus'', including many that are commonly known as locoweeds, do not produce swainsonine. Some species, including a few that produce swainsonine, accumulate [[selenium]]. This has led to confusion between swainsonine poisoning and selenium poisoning due to this genus.<ref>{{Cite web |date=2016-08-28 |title=Ranchers despise locoweed |url=https://www.colorado.edu/asmagazine/2016/08/28/ranchers-despise-locoweed |access-date=2024-05-13 |website=Colorado Arts and Sciences Magazine |language=en}}</ref>

==History and etymology==
The first technical account (in [[English language|English]]) of locoism was published in 1873, in the United States. [[Linguist]]s have documented ''locoism'' in use among English speakers by 1889, and both ''loco'' and ''locoweed'' in use by 1844.<ref name=SmeadSlatta2004>{{cite book
|title=Vocabulario Vaquero/cowboy Talk: A Dictionary Of Spanish Terms From The American West
|author1=Robert N. Smead  |author2=Richard W. Slatta
 |publisher=University of Oklahoma Press
|year=2004
|isbn=978-0-8061-3631-8
|pages=197
|url=https://books.google.com/books?id=MR4SY5n3_L8C
}} page 115</ref>

''Loco'', a [[loanword]] from [[Spanish language|Spanish]], is understood by most English-speaking users in the sense of ''crazy'', and this appears to have also been the sense understood by [[vaquero]]s.<ref name=SmeadSlatta2004/> In Spanish, however, ''loco'' has an older, different sense. In [[Spain]], where the native ''Astragalus'' species are not known to cause locoism, for centuries ''loco'' has been applied to some of these species in the sense of ''rambling'': common names include ''yerba loca'' (''hierba loca''; rambling herb) and ''chocho loco'' (rambling lupine).{{cn|date=October 2023}}

The presence of a toxin in locoweed was demonstrated in 1909. Initially, the toxin was reported to be a [[barium]] compound, but that was soon disproved. 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.<ref name=KeelerTu1983p454>[[#KeelerTu1983|Keeler and Tu (1983)]], page 454.</ref>

Since 1982, swainsonine has been isolated from still more plants, some of which also are reported to cause locoism or medical conditions similar to it. The first report of locoism in [[South America]], involving ''Astragalus pehuenches'', was published in 2000.<ref name=Roblesetal2000>{{cite journal
|title=Intoxicación por ''Astragalus pehuenches'' (locoismo) en ovinos Merino de la Patagonia Argentina
|trans-title=''Astragalus pehuenches'' (locoweed) poisoning in a Merino sheep flock in Patagonia Region, Argentina
|year=2000
|author1=C.A. Robles
|author2=C. Saber
|author3=M. Jefrey
|journal=Revista de Medicina Veterinaria
|volume=81
|issue=5
|pages=380–384
|url=http://www.provino.com.ar/salud-animal-s/232-intoxicacion-por-astragalus-pehuenches-locoismo-en-ovinos-merino-de-la-patagonia-argentina
|access-date=March 2, 2017
|archive-date=March 3, 2017
|archive-url=https://web.archive.org/web/20170303051622/http://www.provino.com.ar/salud-animal-s/232-intoxicacion-por-astragalus-pehuenches-locoismo-en-ovinos-merino-de-la-patagonia-argentina
|url-status=dead
}}</ref>

==Taxa producing swainsonine==
Swainsonine is produced by a small number of species, including species in several genera of plants and two genera of fungi.

[[File:Oxytropis sericea.jpg|thumb|''Oxytropis sericea'' in bloom]]
[[File:Astragalus lentiginosus 4.jpg|thumb|''Astragalus lentiginosus'' in fruit]]
[[File:Curtis's botanical magazine (No. 792) (8469881299).jpg|thumb|''Swainsona galegifolia'']]
''Oxytropis'' is distributed throughout western [[North America]], particularly in the [[Great Plains]] and [[Rocky Mountains]]. However, most species of ''Oxytropis'' have narrow habitat requirements and within those habitats are abundant only in unusually wet years.<ref name="RalphsJames1999">{{cite journal
|vauthors=Ralphs MH, James LF | title = Locoweed grazing
| journal = Journal of Natural Toxins
| volume = 8
| issue = 1
| pages = 47–51
|date=February 1999
| pmid = 10091127
}}</ref> The species most frequently encountered by livestock are ''[[Oxytropis lambertii|O. lambertii]]'' (Lambert locoweed, purple locoweed, woolly locoweed) and especially ''Oxytropis sericea'' (white locoweed, white point locoweed, white point loco). Swainsonine has also been found in ''[[Oxytropis campestris|O. campestris]]'' (in [[Canada]]).<ref name=Jonesetal1997p252/>

Some species of ''[[Astragalus (plant)|Astragalus]]'' (milkvetch) are also referred to as locoweed. Swainsonine has been found in:<ref name=Jonesetal1997p252/>
* ''[[Astragalus earlei|A. earlei]]'' (Big Bend loco)
* ''[[Astragalus mollissimus|A. mollissimus]]'' (purple woolly loco)
* ''[[Astragalus pubentissimus|A. pubentissimus]]'' (green river milkvetch)
* ''[[Astragalus lentiginosus|A. lentiginosis]]'' (spotted locoweed, freckled milkvetch)
* ''[[Astragalus wootoni|A. wootoni]]'' (garbancillo)
* ''[[Astragalus nothoxys|A. nothoxys]]'' (sheep milkvetch)
* ''[[Astragalus tephrodes|A. tephrodes]]'' (ashen milkvetch)
* ''[[Astragalus humistratus|A. humistratus]]'' (ground cover milkvetch)

In [[Argentina]], locoism (''locoismo'') was first reported in 2000. A flock of sheep grazing a pasture with ''[[Astragalus pehuenches]]'' was poisoned and 220 sheep (73%) died.<ref name=Roblesetal2000/> Although this was the first report of locoism in [[South America]],<ref name=Roblesetal2000/> swainsonine had been isolated previously from ''A. pehuenches'' and several other species in Argentina and [[Peru]].<ref name=Roblesetal2000/><ref name=Michael1997>{{cite journal
| author = Michael JP
| title = Indolizidine and quinolizidine alkaloids
| journal = Natural Product Reports
| volume = 14
| issue = 6
| pages = 619–36
|date=December 1997
| pmid = 9418297
| doi = 10.1039/NP9971400619 }}</ref>

In the [[Old World]], native plants causing locoism have not been reported. ''[[Astragalus lusitanicus]]'' in [[Morocco]] was suspected,<ref name="pmid9830691">{{cite journal
|vauthors=Abdennebi EH, el Ouazzani N, Lamnaouer D | title = Clinical and analytical studies of sheep dosed with various preparations of ''Astragalus lusitanicus''
| journal = Veterinary and Human Toxicology
| volume = 40
| issue = 6
| pages = 327–31
|date=December 1998
| pmid = 9830691
}}</ref> but has been shown be neither a producer of swainsonine nor an accumulator of selenium. Its toxicity is suspected to be due to a novel [[alkaloid]].<ref name="pmid10709444">{{cite journal
|vauthors=Ouazzani N, Lamnaouer D, Abdennebi EH | title = Toxicology of ''Astragalus lusitanicus'' Lam
| journal = Thérapie
| volume = 54
| issue = 6
| pages = 707–10
| year = 1999
| pmid = 10709444
}}</ref>

In [[Australia]], species of ''[[Swainsona]]'' (Darling pea) that cause pea struck include:<ref name=Jonesetal1997p252>[[#Jonesetal1997|Jones et al. (1997)]], page 752.</ref><ref>{{cite web
 |title       = Poisonous plant: Darling pea (''Swainsona'' spp.)
 |author      = Les Tanner
 |date        = August 2003
 |publisher   = Northern Inland Weeds Advisory Committee
 |url         = http://www.northwestweeds.nsw.gov.au/Poisonous%20plants%20label%20-%20darling%20pea.pdf
 |accessdate  = May 11, 2009
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20050615213946/http://northwestweeds.nsw.gov.au/Poisonous%20plants%20label%20-%20darling%20pea.pdf
 |archive-date = June 15, 2005
}}</ref>
* ''[[Swainsona luteola|S. luteola]]''
* ''[[Swainsona greyana|S. greyana]]'' (hairy Darling pea)
* ''[[Swainsona galegifolia|S. galegifolia]]'' (smooth Darling pea)

''Astragalus'' and ''Oxytropis'' are two of 20 genera (and 78 names of genera) in the tribe [[Galegeae]], subtribe Astragalinae. Some authorities include ''Swainsona'' in the subtribe.<ref>{{cite web
 |url         = http://www.ars-grin.gov/cgi-bin/npgs/html/gnlist.pl?1504
 |title       = GRIN Genera of Fabaceae subtribe Astragalinae
 |year        = 2003
 |accessdate  = May 12, 2009
 |publisher   = Germplasm Resources Information Network
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20081015234011/http://www.ars-grin.gov/cgi-bin/npgs/html/gnlist.pl?1504
 |archive-date = October 15, 2008
}}</ref> Formerly, ''Swainsona'' was in another subtribe, Coluteinae, that has been combined into Astragalinae.

Swainsonine has also been isolated from ''[[Sida carpinifolia]]'' and ''[[Ipomoea carnea]]'', and both species have been reported to cause locoism.<ref name="pmid12717675">{{cite journal
| author = Carod-Artal FJ
| title = [Neurological syndromes linked with the intake of plants and fungi containing a toxic component (I). Neurotoxic syndromes caused by the ingestion of plants, seeds and fruits]
| language = es| journal = Revista de Neurología
| volume = 36
| issue = 9
| pages = 860–71
| year = 2003
| pmid = 12717675
| url = http://www.revneurol.com/LinkOut/formMedLine.asp?Refer=2003018&Revista=Revneurol
| accessdate = May 13, 2009
}}</ref>

''[[Embellisia]]'', a [[fungus]] isolated from ''Oxytropis lambertii'', has also been shown to produce swainsonine and to cause locoism in rats.<ref name="pmid15309966">{{cite journal
 |vauthors   = McLain-Romero J, Creamer R, Zepeda H, Strickland J, Bell G
 |title      = The toxicosis of ''Embellisia'' fungi from locoweed (''Oxytropis lambertii'') is similar to locoweed toxicosis in rats
 |journal    = Journal of Animal Science
 |volume     = 82 | issue = 7 | pages = 2169–74
 |date       = July 2004
 |pmid       = 15309966 |doi = 10.2527/2004.8272169x }}</ref> ''[[Rhizoctonia leguminicola]]'', a fungal [[Plant pathology|plant pathogen]] that may occur on red clover (''[[Trifolium pratense]]''), also produces swainsonine. Although intoxication due to this fungus resembles locoism, it has additional signs and symptoms due to the production of other toxins.<ref name="pmid7665382">{{cite journal
 |vauthors=Croom WJ, Hagler WM, Froetschel MA, Johnson AD
 |title=The involvement of slaframine and swainsonine in slobbers syndrome: a review
 |journal=Journal of Animal Science  |volume=73  |issue=5  |pages=1499–1508  |date=May 1995  |pmid=7665382  |doi= 10.2527/1995.7351499x}}</ref>

==Pathology==
[[Substance intoxication|Intoxication]] with swainsonine has several kinds of effect.

Livestock that graze for several weeks on locoweed (and little else) develop a [[lysosomal storage disease]] similar to genetic [[mannosidosis]].<ref name="pmid10091126">{{cite journal
|vauthors=Stegelmeier BL, James LF, Panter KE, Ralphs MH, Gardner DR, Molyneux RJ, Pfister JA | title = The pathogenesis and toxicokinetics of locoweed (''Astragalus'' and ''Oxytropis'' spp.) poisoning in livestock
| journal = Journal of Natural Toxins
| volume = 8
| issue = 1
| pages = 35–45
|date=February 1999
| pmid = 10091126
}}</ref> Swainsonine inhibits a [[Lysosome|lysosomal]] [[enzyme]], [[Alpha-mannosidosis|alpha-mannosidase]].<ref name=Jonesetal1997p31>[[#Jonesetal1997|Jones et al. (1997)]], page 31.</ref> This results in abnormal accumulation of the molecules normally processed by the enzyme, and this accumulation leads to [[Vacuole|vacuolation]] of most tissues. Vacuolation is most obvious in [[neuron]]s and [[epithelial cell]]s. The vacuolation resolves shortly after poisoning is discontinued, but if the vacuolation is so severe that it destroys cells, it may result in some neurologic damage that is irreversible and permanent.<ref name="pmid10091126"/> The damage is highly varied. In cattle at [[high altitude]], complications of locoism can include [[congestive heart failure]].<ref name=Merck>{{cite journal
|url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/11400.htm
|title=High-mountain Disease: Introduction|journal=The Merck Veterinary Manual
|year=2008|accessdate=May 11, 2009}}</ref>

== Diagnosis ==
[[Medical diagnosis|Diagnosis]] of clinical poisoning is generally made by documenting exposure, identifying the neurologic signs, and analyzing [[blood serum]] for alpha-mannosidase activity and swainsonine.<ref name="pmid10091126"/>

In [[mule deer]], clinical signs of locoism are similar to [[chronic wasting disease]]. [[Histology|Histological]] signs of vacuolation provide a [[differential diagnosis]].<ref name="pmid16145203">{{cite journal
| vauthors = Stegelmeier BL, James LF, Gardner DR, Panter KE, Lee ST, Ralphs MH, Pfister JA, Spraker TR
| title = Locoweed (''Oxytropis sericea'')-induced lesions in mule deer (''Odocoileius hemionus'')
| journal = Veterinary Pathology
| volume = 42
| issue = 5
| pages = 566–78
| date = September 2005
| pmid = 16145203
| doi = 10.1354/vp.42-5-566
| url = https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=31601&content=PDF
| doi-access = 
| s2cid = 2219085
| url-access = subscription
}}{{Dead link|date=November 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

[[Sub-clinical]] intoxication has been investigated in cattle grazing on ''Astragalus mollissimus''. As the estimated intake of swainsonine increased, [[blood serum]] alpha-mannosidase activity and [[albumin]] decreased, and [[alkaline phosphatase]] and [[thyroid hormone]] increased.<ref name="pmid7858027">{{cite journal
|vauthors=Stegelmeier BL, Ralphs MH, Gardner DR, Molyneux RJ, James LF | title = Serum alpha-mannosidase activity and the clinicopathologic alterations of locoweed (''Astragalus mollissimus'') intoxication in range cattle
| journal = Journal of Veterinary Diagnostic Investigation
| volume = 6
| issue = 4
| pages = 473–9
|date=October 1994
| pmid = 7858027
| doi = 10.1177/104063879400600412
| doi-access = 
| s2cid = 32914209
}}</ref>

== Prevention ==
Because ''O. sericea'' is both frequently encountered and relatively [[palatable]] to livestock, it is an important cause of economic losses in livestock production. Keeping livestock away from locoweed-infested pasture in spring and fall when grass and other forbs are not actively growing is recommended. Another suggested remedy is to provide palatable supplemental nutrients if animals are to be kept in infested pasture. These remedies take into account livestock preference for locoweed during seasons when grass is dry and not very nutritious.<ref>{{Cite web |title=ARS and New Mexico Scientists Take a Long Look at Livestock and Locoweed : USDA ARS |url=https://www.ars.usda.gov/news-events/news/research-news/2010/ars-and-new-mexico-scientists-take-a-long-look-at-livestock-and-locoweed/ |access-date=2024-12-07 |website=www.ars.usda.gov}}</ref> [[Conditioned food aversion]] has been used experimentally to discourage livestock from eating it.<ref name="pmid10817148">{{cite journal
|vauthors=Ralphs MH, Provenza FD | title = Conditioned food aversions: principles and practices, with special reference to social facilitation
| journal = Proceedings of the Nutrition Society
| volume = 58
| issue = 4
| pages = 813–20
|date=November 1999
| pmid = 10817148
| doi =10.1017/S002966519900110X | doi-access = free
}}</ref><ref name=Pfisteretal2002>{{cite journal
 |vauthors     = Pfister JA, Stegelmeier BL, Cheney CD, Ralphs MH, Gardner DR
 |title        = Conditioning taste aversions to locoweed (''Oxytropis sericea'') in horses
 |journal      = Journal of Animal Science
 |volume       = 80
 |issue        = 1
 |pages        = 79–83
 |date         = January 2002
 |pmid         = 11831531
 |doi          = 10.2527/2002.80179x
 |url          = https://pubag.nal.usda.gov/download/4302/PDF
 |issn         = 0021-8812
 |accessdate   = January 28, 2018
 |archive-date = January 29, 2018
 |archive-url  = https://web.archive.org/web/20180129004753/https://pubag.nal.usda.gov/download/4302/PDF
 |url-status   = dead
|url-access= subscription
 }}</ref> In horses, a small study has shown promising results using [[lithium chloride]] as the [[aversive agent]].<ref name=Pfisteretal2002/>

==See also==
* [[List of plants poisonous to equines]]
* [[Nutrition disorder]]

== References ==
{{reflist}}

==Further reading==
* {{cite book
|title=Veterinary pathology
|author=Jones, T. C. |author2=R. D. Hunt |author3=N. W. King
|edition=6th
|publisher=Wiley-Blackwell
|year=1997
|isbn= 978-0-683-04481-2
|pages=1392
|url=https://books.google.com/books?id=8fXzJrDfFgUC
|ref=Jonesetal1997}}
* {{cite book
|title=Plant and fungal toxins
|editor=Keeler, R. F. |editor2=A. T. Tu
|publisher=Marcel Dekker
|year=1983
|isbn=978-0-8247-1893-0
|pages=934
|url=https://books.google.com/books?id=DtUO6fgC4w4C
|ref=KeelerTu1983}}

== External links ==
{{wiktionary|loco|weed}}
{{wiktionary}}
* [https://web.archive.org/web/20060905191024/http://www.lib.k-state.edu/wildflower/whitelocoweed.html White Locoweed - Kansas State University]
* [https://web.archive.org/web/20060905184449/http://www.lib.k-state.edu/wildflower/lambert.html Purple LocoWeed - Kansas State University]
* [http://www.ars.usda.gov/Services/docs.htm?docid=9948 Locoweed - ARS/USDA]
* [https://web.archive.org/web/20060505000604/http://extension.usu.edu/rangeplants/forbs/astragalus.htm Astragalus species of locoweed - Utah State University]

{{Poisoning and toxicity}}

[[Category:Astragalus]]
[[Category:Oxytropis]]
[[Category:Swainsona]]
[[Category:Drugs acting on the nervous system]]
[[Category:Intoxication]]
[[Category:Plant common names]]