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

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

Myxobolus cerebralis Life Cycle: salmonid tubifex triactinomyxon myxospores

DOCUMENTED INTRODUCTIONS OF M. cerebralis-POSITIVE TROUT INTO IDAHO WATERS. 1986. Palouse area farm pond. Rainbow trout from northeast Oregon.* 1985-87. Lost River Trout Farm. Rainbow trout from California. 1993 & 2004: Canyon Spring Trout Farm. Rainbow trout from Utah. * 1966-75. Nevada Div. Wildlife. Rainbow trout from Truckee National Hatchery stocked into streams that cross the state border. *Have apparently not lead to established infection.

Susceptibility of Salmonid Species To M. cerebralis

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

Idaho Department of Fish and Game Hatcheries Pahsimeroi Sawtooth

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 (%) 0 0 20 95 88 80 95 85 55 19 13 5 Degrees C 2.6 3.6 6.1 7.2 11.2 14.1 13.0 11.4 7.1 3.3 2.9 3.2 Hydrograph (CFS) 110 110 250 1570 2190 470 341 304 258 180 123 118

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, 2000- Jan, 2001. 140 43 18 143 1 139 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 (%) 67 85 100 100 90 100 100 80 100 86 91 80 Degrees C 5.0 6.4 9.2 10.3 12.0 13.1 13.5 11.9 9.3 5.8 3.2 3.4 Hydrograph 329 327 300 135 133 109 175 175 284 300 311 321

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

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%

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%

Myxobolus cerebralis Observations in Natural Steelhead and Chinook for the Period 1987 – 2006 Organized by IDFG Regions REGION 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 Curet Eagle Fish Health Laboratory and Salmon Region Idaho Department of Fish and Game

Lemhi Exposure I June ‘03 Positive Negative

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

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

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

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

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

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

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 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

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

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

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

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.

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

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

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

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

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

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 10-100 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

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 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

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

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

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