1. Whirling Disease (Myxobolus cerebralis) and Idaho Fisheries
Keith Johnson
Ret’d Supervisor, IDFG Fish Health Program
Eagle Fish Health Laboratory
Eagle, Idaho

2. Signs: black-tail, spinal curvature, :dolphin head"

3. Myxobolus cerebralis Life Cycle:
salmonid
tubifex
triactinomyxon
myxospores

5. DOCUMENTED INTRODUCTIONS OF M. cerebralis-POSITIVE TROUT
INTO IDAHO WATERS.
Palouse area farm
pond. Rainbow trout from
northeast Oregon.*
Lost River Trout Farm.
Rainbow trout from California.
1993 & 2004: Canyon Spring Trout
Farm. Rainbow trout from
Utah. *
Nevada Div. Wildlife. Rainbow trout from Truckee National Hatchery stocked into streams that cross the state border.
*Have apparently not lead
to established infection.

6. Susceptibility of Salmonid Species To M. cerebralis

8. Dynamic Relationship of Host/Parasite/Environment
Presence, No Disease:
M. cerebralis spores rare, no disease signs,
host population resilient
Ex: S.F. Snake R, S.F. Boise R, M.F. Salmon R
PARASITE
ENVIRONMENT
Disease, No Impact:
Prevalence and intensity of infection high,
disease signs occasional, host population
resilient
Ex: Big Wood R, upper Salmon R, Lemhi R
HOST
PARASITE
ENVIRONMENT
HOST
ENVIRONMENT
PARASITE
Negative Population Impact:
Spores and pathology abundant, disease signs common, host population is parasite limited
Ex: Big Lost R, Little Lost R, Pahsimeroi R

9. Idaho Department of Fish and Game Hatcheries
Pahsimeroi
Sawtooth

10. Figure 1. Prevalence and intensity of M
Figure 1. Prevalence and intensity of M. cerebralis infection of sentinel rainbow trout exposed for ten days to the Salmon River water supply of Sawtooth Hatchery, Feb, 2000-Jan, 2001. .
139 10
144
109 22 88 2 15 7 50 6 54 53 4 4 24 23 5 4 22 5 7 5
Prevalence (%)
Degrees C
Hydrograph (CFS)

11. Figure 2. Prevalence and intensity of M
Figure 2. Prevalence and intensity of M. cerebralis infection of sentinel rainbow trout exposed for ten days to the river water supply of Pahsimeroi Hatchery, Feb, Jan, 2001.
140 43 18
143 56
102 19 23 52
127 52 15 15
194 17 53 26 46
266 4 4 5 2 4 21 25 58 28 7 25 7 8 6 3 68 3
Prevalence (%)
Degrees C
Hydrograph

12. Effect of delaying exposure of Chinook juveniles to river water at Sawtooth and Pahsimeroi hatcheries on detection of M. cerebralis at pre-release sampling the following spring.
Exposure Date

13. Detection of M. cerebralis from Chinook and steelhead adults at Upper Salmon River trap locations. Return years
Return Years

14. UPPER SALMON R

15. Distribution of Myxobolus cerebralis within the Salmon River
during the migration period of 2001 for juvenile anadromous
salmonids
Wade Cavender
JAAH 2003

16. Snake River 10 9 7 8 5 6 4 3 2 1 NF Salmon River Lemhi R.
Pahsimeroi R. 2
EF Salmon 1

17. April    Snake River OFH PFH STFH 15% 100% 100% 0% 60% Lemhi R.
NF Salmon River
OFH
15% 
100%
Lemhi R.
Snake and Clearwater rivers of Idaho
Increasing infectivity
Below the middle fork of the Salmon
Also indicated that the parasite is present within the the Salmon river drainage during juvenile migration periods
Relationship between environmental parameters and prevalence suggest infectivity may be influenced by water chemistry and discharge in this system
100%
PFH  0%
Pahsimeroi R.
STFH 
EF Salmon
60%

18. May    Snake River OFH PFH STFH 15% 100% 20% 100% 90% 100% 100%
NF Salmon River
OFH
100% 
20%
100%
Lemhi R.
1. Results thus far provide a clear picture of the current status of t he parasite within these drainages.
90%
PFH 
100%
Pahsimeroi R.
STFH 
EF Salmon
100%

19. Myxobolus cerebralis Observations in Natural Steelhead and Chinook for the Period 1987 – Organized by IDFG Regions
REGION STEELHEAD CHINOOK Clearwater / / Southwest / / Salmon /192 (11.5%) 262/2066 (12.7%)

20. Implications of Tributary Reconnection to Establishing Myxobolus cerebralis in the Lemhi River Drainage, Idaho
Keith Johnson and Tom Curet
Eagle Fish Health Laboratory and Salmon Region
Idaho Department of Fish and Game

21. Lemhi Exposure I June ‘03
Positive
Negative

22. Lemhi Exposure II Oct’03
Hayden Cr
100%
Positive
Negative

23. Reconnection of Lemhi River Tributaries:
Would not expand the existing range of
the parasite since it is already present, regardless of tributary connection status
Basin Creek may be the origin of infectivity in the Hayden Creek drainage but ponds a source also

24. Does M. cerebralis limit natural
Trout production in the Teton
River ?
Martin Koenig
Utah State University
Application of the UofI epidemiological model of Anlauf, Colvin, & Moffitt

25. Teton River  Teton Creek Fox Creek Teton R. Trail Creek
Teton I exposure (Aug,’03) prevalence and intensity (x’000) of M. cerebralis infection
Teton River 
Flow
Teton Creek
Fox Creek
Teton R.
Trail Creek

26. Anemic challenges in the first Teton River exposure indicate a low probability that M. cerebralis infections could limit natural
production of salmonids.

27. Teton II exposure (July,’04) prevalence and intensity (x’000) of M
Teton II exposure (July,’04) prevalence and intensity (x’000) of M. cerebralis infection
100 (40)
Teton River
Flow 
Teton Creek
(69)
(16)
50 (2)
(23)
Unnamed Creek
(39)
(18)
(39)
Fox Creek
(41)
Teton R.
Trail Creek

28. Implications from Teton River Trials
Exposures made in 2004 resulted in higher prevalence and intensity of M. cerebralis infection than in 2003, annual variation in exposure must be considered
Habitat differences throughout study area varied only slightly
Population declines were apparent in Yellowstone cutthroat, not rainbow trout even though both species are highly susceptible
Tubifex habitat characteristics and susceptibility lineages are needed
Unnamed Creek may provide fry a refuge from intense challenge

29. Application of Risk Assessment to Whirling Disease in Idaho
Introduction
Isolation of new waters, prevent movement
Establishment & Amplification
Need an understanding of what environmental mechanisms operate to limit parasite numbers
Persistence
Need to demonstrate the probability that M. cerebralis will not persist and in what time period, the incentive for painful change

30. Persistence of M. cerebralis: Will the infection fade into the sunset?
Modin (1998) reported infections decreased to below detectable limits when positive rearing facilities in California were closed in 3 of 22 waters over a 32-year period
Cache de Poudre River (Colorado Division of Wildlife) infections were no longer detectable two years after an earthen rearing pond ceased rearing trout (Nehring, 2003)
Hayspur Hatchery (IDFG) switched to well water in 1993 and we can no longer detect the parasite
These examples show the parasite may not persist in certain waters
and support enforcement of IDFG’s role in private pond management

31. A TRIBUTARY TO SILVER CREEK IN SOUTH CENTRAL IDAHO
PROBABLE INFLUENCE OF IRRIGATION WATER DIVERSION ON Myxobolus cerebralis-INFECTIVITY AT HAYSPUR HATCHERY AND IN LOVING CREEK,
A TRIBUTARY TO SILVER CREEK IN SOUTH CENTRAL IDAHO

32. N S W E Big Wood River Bellevue Loving Creek Hayspur Hatchery
Gannett
Big Wood River
Loving Creek
Hayspur Hatchery
Silver Creek
5 km
Stalker Creek

33. HISTORY OF HAYSPUR HATCHERY
Built 1906.
Peak annual production of 1 million rainbow trout fingerling and 350,000 rainbow catchables.
Myxobolus spores first detected from adult fish in the brood pond in 1988; confirmed M. cerebralis in 1989.
Reconstruction began in 1989.
All use of surface water for production ceased in 1995.

34. SENTINEL EXPOSURE DATES
4/03
6/03
9/03
3/04
5/04
6/04
10/04
HATCHERY INTAKE X
BROOD POND
GAVER LAGOON
RAILROAD TRESTLE
KILPATRICK BRIDGE
IRRIGATION CANAL
BIG WOOD RIVER
EXPOSURE SITES

35. Hayspur Hatchery sites
Bellevue N W E S
Big Wood River
3 exposures; 64/112 fish (57%)
Irrigation Canal
2 exposures; 80/81 fish (99%)
Hayspur Hatchery sites
Intake
4 exposures; 0/133 fish
Brood Pond
Gannett
Big Wood River
4 exposures; 0/101 fish
Loving Creek
Railroad Trestle
Hayspur Hatchery
7 exposures; 0/197 fish
Gaver Lagoon
4 exposures; 0/122 fish
Silver Creek
Kilpatrick Bridge
5 km
Stalker Creek
7 exposures; 0/217 fish

36. 2006 N S Irrigation Canal Intake Loving Creek Diversion
Bellevue N
2006 W E
Heavy snowpack = extended runoff S
Irrigation Canal
1 exposure; 47/47 fish (100%)
Intake
2 exposures; 0/88 fish
Gannett
Big Wood River
Loving Creek
Loving Creek Diversion
Railroad Trestle
Hayspur Hatchery
2 exposures; 1/84 fish
2 exposures; 0/75 fish
Silver Creek
Kilpatrick Bridge
5 km
Stalker Creek
2 exposures; 0/86 fish

37. Conclusions from the Hayspur Hatchery Exposures:
M. cerebralis detections at Hayspur H. during the ‘88-’93 period was sporadic and low in prevalence (<2%)
Parasite did not become established in Silver Creek
Irrigation water from Big Wood River canals was the likely source of infection during 1988 to 1993 but even adjacent spring creeks have not become infected
So….parasite was introduced but did not persist
Implications for private pond permitting process, we may not have to live with this parasite in all cases

38. Management Solutions:
Resistant strains of Hofer rainbow trout:
CDOW, UC Davis, U Munich teaming on applications.
1. Resistance is inherited from both parents and operates early in parasite migration
2. Lower spore counts, fewer signs, and lower histology scores characterize infections in Hofer RBT
3. Hofer x wild RBT stocks being evaluated in CO & UT
Not stocking positive trout is common to sites where M. cerebralis does not persist
Land use also has a role in persistence

39. CDOW Resistant Trout Research (Schisler,’07)
Growth in hatchery for Hofer RBT was superior
compared to CDOW hatchery strains
Evaluations of spore counts after planting showed reduction by fold
Return-to-creel in two lakes was 15% higher
Utah DWR is conducting similar trials
Commercial trout suppliers in Co and CA have Hofer RBT to stock

40. CDOW ’09 Hofer X CRR RBT Hybrid Evaluations
Hybrids and CRR controls stocked in two river systems for four years
Hybrids had higher survival than CRR controls
Post-stocking survival was best when stocked at >9” TL to avoid predation by BNT
Some natural reproduction has been detected in both rivers
Hofer genetic markers have exceeded CRR markers in natural fry
CDOW will continue stocking hybrids and monitoring natural production of hybrids vs controls

41. So now I get to speculate on why whirling disease does not cause levels
of impact in Idaho as reported in MT and CO….
Habitats within the shaded area in which population impacts are suspected are all:
Volcanic tuft soils, easily eroded
Abundant groundwater, stable water temperature
Eutrophic, highly productive
High level of grazing impacts
Low gradient river bottoms
Tubifex habitat and lineages
are important to examine

42. Big & Little Lost, Birch Creek, and Teton R on
Shaded drainages have aquatic habitats conducive to amplification: Pahsimeroi, Lemhi,
Big & Little Lost, Birch Creek, and Teton R on
a bad year
HOST
ENVIRONMENT
PARASITE ?
Drainages outside of the shaded area are basaltic and granitic origin, lack amplification after
parasite was introduced
HOST
PARASITE
ENVIRONMENT

43. Administer private pond stocking to reduce risk of parasite spread
PLANS FOR THE FUTURE
Expand knowledge on distribution and epidemiology of M. cerebralis: Upper Salmon River and role of carcasses
Cooperate with ISDA and industry to reduce WD range and intensity through Invasive Species legislation
Administer private pond stocking to reduce risk of parasite spread
Monitor Hofer RBT resistance research and explore application for Idaho
Educate regional biologists, conservation officers and anglers about whirling disease

44. Thanks to Idaho Power Company
for this $12 M investment!