Whirling Disease (Myxobolus cerebralis)andIdaho FisheriesKeith JohnsonRetd Supervisor, IDFG Fish Health ProgramEagle Fish Health LaboratoryEagle, Idaho

myxospores

DOCUMENTED INTRODUCTIONSOF M. cerebralis-POSITIVE TROUTINTO IDAHO WATERS.1985-87. Lost River Trout Farm.Rainbow trout from California.1993 & 2004: Canyon Spring TroutFarm. Rainbow trout fromUtah. **Have apparently not lead to established infection.1966-75. Nevada Div. Wildlife. Rainbow trout from Truckee National Hatchery stocked into streams that cross the state border.1986. Palouse area farmpond. Rainbow trout fromnortheast Oregon.*

Susceptibility of Salmonid Species To M. cerebralis

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HighModerateLowRefractory

RBT/STHChinookBrook TroutLake Trout

CutthroatSockeyeBrown TroutBull Trout

Mtn WhitefishCoho

Grayling

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Dynamic Relationship of Host/Parasite/EnvironmentHOSTPARASITEENVIRONMENTENVIRONMENTHOSTPARASITEPresence, No Disease:M. cerebralis spores rare, no disease signs,host population resilientEx: S.F. Snake R, S.F. Boise R, M.F. Salmon R

Disease, No Impact:Prevalence and intensity of infection high,disease signs occasional, host populationresilient Ex: Big Wood R, upper Salmon R, Lemhi R

Negative Population Impact:Spores and pathology abundant, disease signs common, host population is parasite limitedEx: Big Lost R, Little Lost R, Pahsimeroi R

Idaho Department of Fish and Game HatcheriesSawtoothPahsimeroi

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. Prevalence (%)0 0209588 80 95855519135Degrees C2.6 3.66.17.211.214.113.011.47.13.32.93.2Hydrograph (CFS)110 11025015702190470341304258180123118 7 5 22 53 88 5 22 23 54 109 50 139 5 7144 24 15 4 44 6 2.10

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, 2000- Jan, 2001. Prevalence (%) 6785 100 10090 100 100 80 100869180Degrees C 5.0 6.4 9.2 10.3 12.0 13.1 13.5 11.9 9.35.83.23.4Hydrograph 329 327 300 135 133 109 175 175 2843003113215626 102 47 684625 6 7 21 143 52127 817 266 19425 358 19 4 15 1 139 53 283 22343 415521405 18

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

Detection of M. cerebralis from Chinook and steelhead adults at Upper Salmon River trap locations. Return years 1987-2006.Return Years

UPPER SALMON R

Distribution of Myxobolus cerebralis within the Salmon River during the migration period of 2001 for juvenile anadromous salmonids

Wade Cavender JAAH 2003

Snake River12NF Salmon River345678910EF SalmonLemhi R.Pahsimeroi R.

AprilEF SalmonPahsimeroi R.Snake RiverNF Salmon RiverSTFHPFHOFHLemhi R.60%0%100%15%100%

MayEF SalmonPahsimeroi R.Snake RiverNF Salmon RiverSTFHPFHOFHLemhi R.100%90%100%100%20%15%100%

Myxobolus cerebralis Observations in Natural Steelhead and Chinook for the Period 1987 2006 Organized by IDFG RegionsREGION STEELHEAD CHINOOK Clearwater 0/301 0/428 Southwest 0/57 0/493 Salmon 22/192 (11.5%) 262/2066 (12.7%)

Implications of Tributary Reconnection to Establishing Myxobolus cerebralis in the Lemhi River Drainage, Idaho

Keith Johnson and Tom CuretEagle Fish Health Laboratory and Salmon RegionIdaho Department of Fish and Game

Lemhi Exposure I June 03PositiveNegative

100%Hayden CrLemhi Exposure II Oct03PositiveNegative

Reconnection of Lemhi River Tributaries:

Would not expand the existing range of the parasite since it is already present, regardless of tributary connection statusBasin Creek may be the origin of infectivity in the Hayden Creek drainage but ponds a source also

Does M. cerebralis limit naturalTrout production in the TetonRiver ?

Martin KoenigUtah State University

Application of the UofI epidemiological model of Anlauf, Colvin, & Moffitt

Fox CreekTrail CreekTeton CreekTeton RiverTeton R.FlowTeton I exposure (Aug,03) prevalence and intensity (x000) of M. cerebralis infection

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

Fox CreekTrail CreekTeton CreekTeton RiverTeton R.FlowTeton II exposure (July,04) prevalence and intensity (x000) of M. cerebralis infection 100 (40) (69) (16)50 (2)(23)(39)(39)(18)(41)Unnamed Creek

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negative10

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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

Application of Risk Assessment to Whirling Disease in IdahoIntroductionIsolation of new waters, prevent movementEstablishment & AmplificationNeed an understanding of what environmental mechanisms operate to limit parasite numbers PersistenceNeed to demonstrate the probability that M. cerebralis will not persist and in what time period, the incentive for painful change

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 periodCache 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 parasiteThese examples show the parasite may not persist in certain watersand support enforcement of IDFGs role in private pond management

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

GannettBellevueLoving CreekStalker CreekHayspur HatcherySilver Creek5 kmBig Wood RiverNSWE

HISTORY OF HAYSPUR HATCHERYBuilt 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.

EXPOSURE SITES

SENTINEL EXPOSURE DATES4/036/039/033/045/046/0410/04HATCHERY INTAKEXXXXBROOD PONDXXXXGAVER LAGOONXXXXRAILROAD TRESTLEXXXXXXXKILPATRICK BRIDGEXXXXXXXIRRIGATION CANALXXBIG WOOD RIVERXXX

GannettBellevueLoving CreekStalker CreekHayspur HatcherySilver Creek5 kmBig Wood RiverNSWEGaver LagoonKilpatrick BridgeRailroad TrestleBrood PondIntakeIrrigation Canal Big Wood River7 exposures; 0/217 fish2 exposures; 80/81 fish (99%)3 exposures; 64/112 fish (57%)7 exposures; 0/197 fish4 exposures; 0/133 fish4 exposures; 0/101 fish4 exposures; 0/122 fishHayspur Hatchery sites

GannettBellevueLoving CreekStalker CreekHayspur HatcherySilver Creek5 kmBig Wood RiverNSWEKilpatrick BridgeRailroad TrestleIntakeIrrigation Canal 2 exposures; 0/86 fish1 exposure; 47/47 fish (100%)2 exposures; 1/84 fish2 exposures; 0/88 fish2 exposures; 0/75 fish2006Heavy snowpack = extended runoffLoving Creek Diversion

Conclusions from the Hayspur Hatchery Exposures:

M. cerebralis detections at Hayspur H. during the 88-93 period was sporadic and low in prevalence (

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 migration2. Lower spore counts, fewer signs, and lower histology scores characterize infections in Hofer RBT 3. Hofer x wild RBT stocks being evaluated in CO & UTNot stocking positive trout is common to sites where M. cerebralis does not persistLand use also has a role in persistence

CDOW Resistant Trout Research (Schisler,07)Growth in hatchery for Hofer RBT was superiorcompared to CDOW hatchery strainsEvaluations of spore counts after planting showed reduction by 10-100 foldReturn-to-creel in two lakes was 15% higherUtah DWR is conducting similar trialsCommercial trout suppliers in Co and CA have Hofer RBT to stock

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

So now I get to speculate on why whirling disease does not cause levelsof 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

?Shaded drainages have aquatic habitats conducive to amplification: Pahsimeroi, Lemhi,Big & Little Lost, Birch Creek, and Teton R on a bad yearDrainages outside of the shaded area are basaltic and granitic origin, lack amplification afterparasite was introduced

PLANS FOR THE FUTUREExpand knowledge on distribution and epidemiology of M. cerebralis: Upper Salmon River and role of carcassesCooperate with ISDA and industry to reduce WD range and intensity through Invasive Species legislation Administer private pond stocking to reduce risk of parasite spreadMonitor Hofer RBT resistance research and explore application for IdahoEducate regional biologists, conservation officers and anglers about whirling disease

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

**Signs: black-tail, spinal curvature, :dolphin head"*********Snake and Clearwater rivers of IdahoIncreasing infectivityBelow the middle fork of the SalmonAlso indicated that the parasite is present within the the Salmon river drainage during juvenile migration periodsRelationship between environmental parameters and prevalence suggest infectivity may be influenced by water chemistry and discharge in this system

*1. Results thus far provide a clear picture of the current status of t he parasite within these drainages.