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SCIENTIFIC BREAKTHROUGH HELPS COMBAT TROUT DISEASE (fwd)




---------- Forwarded message ----------
Date: Mon, 27 Jan 97 12:02:05 MST
From: RICH_GREENWOOD@mail.fws.gov
     
U.S. Fish and Wildlife Service
Whirling Disease Foundation
     
January 13, 1997                      Janet Tennyson 202-208-5634
                          Tom Anacker or Sue Higgins 406-585-0860
     
       SCIENTIFIC BREAKTHROUGH HELPS COMBAT TROUT DISEASE
     
A major weapon in the fight against whirling disease--a trout- 
killing infection that is devastating in some wild trout 
populations--has been developed by researchers at the University 
of California-Davis, the U.S. Fish and Wildlife Service and the 
Whirling Disease Foundation announced today.
     
Mr. Karl Andree and Professor Ronald Hedrick at the university's 
School of Veterinary Medicine isolated genes specific to the 
parasite causing whirling disease, allowing scientists to apply a 
special DNA-based test as a diagnostic tool.  The research 
leading to this advance was funded by the U.S. Fish and Wildlife 
Service, the Whirling Disease Foundation, Trout Unlimited, and 
the Montana Department of Fish, Wildlife, and Parks.
     
"This opens up a promising new era in our efforts to protect 
America's prime trout fisheries from whirling disease," said John 
Rogers, Acting Service Director.  "It gives fishery managers an 
early warning system that should enable them to detect this 
disease early and help control its spread."
     
Whirling disease, caused by a microscopic parasite introduced to 
the United States in the 1950s, is believed responsible for the 
decimation of trout populations in some of America's most 
renowned trout streams, especially in the Rocky Mountain West. 
In recent years, whirling disease has been associated with an 
estimated 90-percent decline in Montana's upper Madison River
wild rainbow trout population as well as disastrous rainbow trout 
losses in Colorado's South Platte, Gunnison, and Colorado rivers.
     
This has alarmed scientists and anglers alike, spurring several 
intensive research efforts.
     
Andree and Hedrick isolated genes from Myxobolus cerebralis (the 
parasite causing whirling disease), allowing the use of a modern 
diagnostic test known as the Polymerase Chain Reaction (PCR). 
The test can also detect infections in the parasite's other host, 
the aquatic worm Tubifex tubifex.  The PCR test amplifies even 
very small amounts of the parasite's DNA, allowing its detection 
at much lower levels than previously possible.
     
Refining the PCR method may also allow non-lethal diagnostic 
testing of trout in the future, which scientists consider 
increasingly important in the face of dwindling wild trout 
populations in some locations.  With the new discovery, the PCR 
method can also indicate the parasite's existence in a given body 
of water.  
     
According to Beth MacConnell, the Service's top whirling disease 
biologist stationed at the Bozeman Fish Technology Center in 
Montana, the discovery will be a crucial component of all future 
whirling disease research.  "The new diagnostic tool provides 
speed, accuracy, and sensitivity we simply didn't have before," 
she said.
     
The spores of Myxobolus cerebralis, released when infected fish 
die, are ingested by Tubifex worms, which live in mud.  Inside 
the worm, the parasite takes on a new form, becoming capable of 
infecting young salmonids, especially rainbow trout, before their 
cartilage hardens to bone.  Myxobolus cerebralis gets into the 
cartilage near a fish's organ of equilibrium and multiplies very 
rapidly, sometimes into the millions, pressuring the organ and 
causing the victim to swim erratically, losing its ability to 
forage or to escape predators.
     
The new test is already being used by Professors Robert Ellis at 
Colorado State University and Stuart Knapp at Montana State 
University to analyze infections.
     
The quantitative sensitivity of the PCR tool is being measured in 
Dr. Ellis' lab.  The results of this work will allow fishery 
managers to determine the levels of infection in streams.  The 
data obtained from this research will be correlated with young- 
of-the-year fish surveys to determine the ratio of mortality 
levels to levels of infection.
     
Dr. Knapp's laboratory is using the PCR method to test Tubifex 
worms taken from dozens of Montana streams.  Results will provide 
information on the seasonality of whirling disease, which may 
help scientists develop new management strategies for combatting 
it.
     
The whirling disease parasite has been detected in at least 21 
states:  California, Colorado, Connecticut, Idaho, Maryland, 
Massachusetts, Michigan, Montana, Nevada, New Hampshire, New 
Jersey, New Mexico, New York, Ohio, Oregon, Pennsylvania, Utah, 
Virginia, Washington, West Virginia, and Wyoming.
     
In addition to the $200,000 the Service provided for this 
research, in 1996 the agency joined the National Fish and 
Wildlife Foundation; the Montana Department of Fish, Wildlife, 
and Parks; and the Whirling Disease Foundation to provide a 
$195,000 grant for construction of a whirling disease research 
laboratory at Montana State University.  A secure, contained 
facility was needed to study whirling disease-infected organisms 
to determine fish and worm genetic factors that promote or limit 
parasite growth and investigate methods to control the disease in 
infected watersheds.  In addition, the Service has intensified 
its research efforts to combat whirling disease at its Bozeman 
Fish Technology Center.
     
The Whirling Disease Foundation is co-sponsoring a national 
symposium on whirling disease March 6-8, 1997, in Logan, Utah. 
"This symposium will provide the opportunity for the latest 
research findings on whirling disease to be shared with the 
research community and the public," said Dr. Karl Johnson, 
Science Director of the Whirling Disease Foundation.  
     
Presentations will include reports on the range of the infection 
and distribution of the Tubifex worm, results of comparative 
studies of the sensitivity of different fish species to the 
disease, methods for filtering and quantifying the fish-infective 
state of the parasite from water samples, and investigations into 
the initial interactions between the parasite and the two hosts 
included in its life cycle.
     
                              -FWS-
     
     
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Subject: SCIENTIFIC BREAKTHROUGH HELPS COMBAT TROUT DISEASE
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