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Fish Transfer

Relationship between the life stage of the fish and the likelihood of introducing Myxobolus cerebralis with its movement.
Life stage Source of parasite/parasite stage Likelihood of detection
Eggs* No NA
Fry, alevins Yes/ immature parasite stages Low to high
Juveniles, adults Yes/ spores Moderate to high
*assumes disinfection and no transfer of water or material that might carry the parasite
NA = not applicable

Species Susceptibility

Susceptibility to whirling disease among species of salmonids by laboratory or natural exposure to Myxobolus cerebralis at vulnerable life stages.
Genus Species Common Name Susceptibility*
Oncorhynchus mykiss Rainbow trout 3
  mykiss Steehead trout 3
  clarki Cutthroat trout  
  c. bouveri Yellowstone cutthroat 2
  c. lewisi Westslope cutthroat 2
  c. pleuriticus Colorado River cutthroat 2
  c. virginalis Rio Grande cutthroat 2
  c. stomias Greenback cutthroat 2
  tshawytscha Chinook salmon 2
  nerka Sockeye salmon 3
  keta Chum salmon 1 S
  gorbuscha Pink salmon 1 S
  masu Cherry salmon 1 S
  kisutch Coho salmon 1
Salvelinus fontinalis Brook trout 2
  malma Dolly Varden 1 S
  confluentus Bull trout 1
  namaycush Lake trout 0 S
  Salmo salar Atlantic salmon 2 S
  trutta Brown trout 1
Prosopium williamsoni Mountain whitefish 2 S
Thymallus thymallus European grayling 2 S
  arcticus Artic grayling 0
Hucho hucho Danube salmon 3
*Scale of 0-3 or S: 0=resistant, no spores develop; 1=partial resistance, clinical disease rare and develops only when exposed to very high parasite doses; 2=susceptible, clinical disease common at high parasite doses, but greater resistance to disease at low doses; 3=highly susceptible, clinical disease common; S=susceptibility is unclear (conflicting reports, insufficient data, lack of Myxobolus cerebralis confirmation).

Source Facility History

Risk is reduced when fish come from a facility with a known certified source.

Migration of Wild Fish and Birds

Migratory salmonids—In systems where fish have a resident life history, dispersal by this route may be limited. Fluvial and adfluvial (migrating between lakes and rivers or streams) life histories introduce greater potential for upstream or downstream movement because these fish migrate between spawning tributaries and the mainstem river or lake. Anadromous salmon present the potential for dispersal both within and between drainages. However, in addition to life history, the susceptibility of the species is also important. Species like coho salmon (Oncorhynchus kisutch), although anadromous, present a very low risk because of their low susceptibility to M. cerebralis.
Birds—Viable myxospores have also been demonstrated to pass through the digestive tracts of piscivorous birds and fish. The role of avian vectors in disseminating M. cerebralis is unclear, but perception of its importance has, in part, prompted construction of bird exclusion devices in culture facilities. New studies in progress may present different or new information on this topic.


  • Fish transfer, source facility, and migration information was provided by Jerri Bartholomew.
  • The species susceptibility chart was provided by Beth MacConnell and Dick Vincent.

Full reports on this data can be found in the American Fisheries Society Symposium 29 findings, titled:Whirling Disease: Reviews and Current Topics, Jerri Bartholomew and J. Christopher Wilson, editors.

Also check the following links for more information on detection and transmission...

The Fish Health Section (FHS) of the American Fisheries Society was formed in 1972 to give fish biologists, pathologists, aquaculturists, veterinarians, administrators and those involved in research and development of fish health an organization for communication.

The Blue book is an updated, searchable CD that contains chapters on "Suggested Procedures for the Detection and Identification of Certain Finfish and Shellfish Pathogens" and the newly developed for 2003, "Standard Procedures for Aquatic Animal Health Inspections".