Editing Rainbow trout (section)

====Whirling disease====
{{see also|Salmonid susceptibility to whirling disease}}
{{nowrap|''[[Myxobolus cerebralis]]''}} is a [[myxosporea]]n [[parasite]] of [[Salmonidae|salmonids]] (salmon, trout, and their allies) that causes whirling disease in pen [[Aquaculture of salmonids|farmed salmon]] and trout and also in [[Wild fisheries|wild fish populations]].<ref name=whirlingdiseaseinitiative2009>{{cite web |url=http://whirlingdisease.montana.edu/pdfs/wdi_final_2009.pdf |title=Whirling Disease Initiative: Final Report |date=October 2009 |publisher=Montana Water Center, Montana State University |page=1 |access-date=2013-12-30 |url-status=dead |archive-url=https://web.archive.org/web/20120717065507/http://whirlingdisease.montana.edu/pdfs/wdi_final_2009.pdf |archive-date=2012-07-17 }}</ref> It was first described in rainbow trout introduced to Germany a century ago, but its range has spread and it has appeared in most of Europe, northern Asia, the U.S., South Africa<ref name="S-Afr-CIB">{{cite web | title=Trout impact on distributional patterns of native fish species | website=[[Centre for Invasion Biology]] | date=2021-09-20 | url=http://blogs.sun.ac.za/cib/trout-impact-on-distributional-patterns-of-native-fish-species/ | access-date=2021-09-25 | first=Lerato | last=Maimela}}</ref> and other countries.<ref name=TUWD2009>{{cite web |url=http://fwp.mt.gov/fwpDoc.html?id=40473 |title=Whirling Disease in the United States – A Summary of Progress in Research and Management 2009 |publisher=Whirling Disease Foundation, Trout Unlimited |access-date=2013-12-31 |author1=Elwell, Leah C. Steinbach |author2=Stromberg, Kajsa Eagle |author3=Ryce, Eileen K.N. |author4=Bartholomew, Jerri L. |archive-date=2013-08-28 |archive-url=https://web.archive.org/web/20130828195623/http://fwp.mt.gov/fwpDoc.html?id=40473 |url-status=dead }}</ref> In the 1980s, {{nowrap|''M. cerebralis''}} was found to require ''[[Tubifex tubifex]]'' (a kind of [[Annelid|segmented worm]]) to complete its [[Biological life cycle|life cycle]]. The parasite infects its hosts with its cells after piercing them with [[polar filament]]s ejected from [[cnidocyte|nematocyst]]-like capsules.<ref name=wddescription/>
[[File:Worldwide distribution of Mcerebralis.png|right|thumb|300px|alt=Map of worldwide distribution of Whirling Disease|''M. cerebralis'' has been reported in Germany (1893), Italy (1954), [[USSR]] (1955), including [[Sakhalin]] Island (1960), U.S. (1958), [[Bulgaria]] (1960), [[Socialist Federal Republic of Yugoslavia|Yugoslavia]] (1960), Sweden (1966), South Africa (1966), Scotland (1968), New Zealand (1971), [[Ecuador]] (1971), Norway (1971), [[Colombia]] (1972), [[Lebanon]] (1973), Ireland (1974), Spain (1981) and England (1981).]]
This parasite was originally a mild pathogen of brown trout in central Europe and other salmonids in northeast Asia, and the spread of the rainbow trout has greatly increased its impact. Having no innate [[Immunity (medicine)|immunity]] to {{nowrap|''M. cerebralis''}}, rainbow trout are particularly susceptible, and can release so many spores that even more resistant species in the same area, such as {{nowrap|''Salmo trutta''}}, can become overloaded with parasites and incur mortalities of 80 to 90&nbsp;percent. Where {{nowrap|''M. cerebralis''}} has become well-established, it has caused a decline or even elimination of whole [[Taxonomic rank#All ranks|cohorts]] of fish.<ref>Nehring, R. B. "Whirling Disease in Feral Trout Populations in Colorado". In Bergersen, E. P., and Knopf, B. A. (1996). ''Proceedings, Whirling Disease Workshop, Denver, Colorado, February 6–8, 1996: Where Do We Go from Here?'' Fort Collins, Colorado: Colorado Cooperative Fish and Wildlife Research Unit, pp. 126–144. {{OCLC|37379539}}</ref><ref>Vincent, E. R. "Whirling Disease – the Montana Experience, Madison River". In Bergersen, E. P., and Knopf, B. A. (1996). ''Proceedings, Whirling Disease Workshop, Denver, Colorado, February 6–8, 1996: Where Do We Go from Here?'' Fort Collins, Colorado: Colorado Cooperative Fish and Wildlife Research Unit, p. 159. {{OCLC| 37379539}}</ref>

The parasite {{nowrap|''M. cerebralis''}} was first recorded in North America in 1956 in Pennsylvania,<ref name=wddescription>{{cite web |url=http://www.ncrac.org/NR/rdonlyres/3CBECF1E-2AE0-4661-9C08-29A0A15DE403/26267/Whirling2.pdf |title=What Is Whirling Disease? |publisher=North Central Regional Aquaculture Center and Michigan State University Extension |date=December 2004 |access-date=2013-12-31 |author1=Faisal, Mohamed |author2=Garling, Donald |url-status=dead |archive-url=https://web.archive.org/web/20140101073322/http://www.ncrac.org/NR/rdonlyres/3CBECF1E-2AE0-4661-9C08-29A0A15DE403/26267/Whirling2.pdf |archive-date=2014-01-01 }}</ref> but until the 1990s, whirling disease was considered a manageable problem affecting only rainbow trout in hatcheries. It eventually became established in the natural waters of the Rocky Mountain states ([[Colorado]], Wyoming, [[Utah]], [[Montana]], [[Idaho]], [[New Mexico]]), where it is damaging several sport fishing rivers. Some streams in the western U.S. lost 90&nbsp;percent of their trout.<ref>{{cite web |date=January 13, 1997 |title=Scientific Breakthrough Helps Combat Trout Disease |publisher=U.S. Fish and Wildlife Service Whirling Disease Foundation News Release| url=http://www.fws.gov/mountain-prairie/pressrel/97-01.HTM |author1=Tennyson, J. |author2=Anacker, T. |author3=Higgins, S. |access-date=2014-01-05}}</ref> Whirling disease threatens recreational fishing, which is important for the tourism industry, a key component of the economies of some U.S. western states. For example, in 2005 anglers in Montana spent approximately $196,000,000 in activities directly related to trout fishing in the state.<ref>{{cite web |url=http://www.montanatrout.org/native.html |title=Montana's Wild Trout |publisher=The Trout Conservancy |archive-url=https://web.archive.org/web/20140101135600/http://www.montanatrout.org/native.html |archive-date=2014-01-01}}</ref> Some of the salmonids that {{nowrap|''M. cerebralis''}} infects ([[bull trout]], [[cutthroat trout]], and anadromous forms of rainbow trout—steelhead) are already threatened or endangered, and the parasite could worsen their population decline.<ref name="Gilbert">{{cite journal |last1=Gilbert |first1=M. A. |last2=Granath |first2=W. O. Jr. |year=2003 |title=Whirling Disease and Salmonid Fish: Life Cycle, Biology, and Disease |journal=Journal of Parasitology |volume=89 |issue=4 |pages=658–667 |doi= 10.1645/GE-82R|jstor=3285855 |pmid=14533670 |s2cid=8950955 }}</ref>