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A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
In this posting:
[1] Utah: kokanee salmon
[2] Maryland: rainbow trout
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[1] Utah: kokanee salmon
Date: Wed 18 May 2011
Source: The Salt Lake Tribune [edited]
Flaming Gorge Reservoir. Add yet another name to the list of
predators chasing kokanee salmon at Flaming Gorge Reservoir and its
tributaries. But unlike other fish, this new threat can't be seen
coming because it is microscopic.
Kokanee salmon [aka sockeye or red salmon] have joined the list of
fish species in the state infected with whirling disease. The
discovery came last fall [2010] during an annual disease
certification, when 9 of the 60 fish pulled from Sheep Creek -- a
popular spawning run for the introduced and non-native salmon -- came
up with spores from the whirling disease parasite.
"This was just another blow to kokanee that we didn't need," said
Ryan Mosley, Flaming Gorge project leader for the Utah Division of
Wildlife Resources (DWR).
Whirling disease attacks juvenile trout and salmon and can lead to
deformities and death.
The kokanee at the Gorge already have a number of serious threats.
Lake trout, another non-native species, dine on the salmon, and
burbot, a ferocious and illegally introduced predator, recently
entered the reservoir and also have a major craving for kokanee. Even
mammals are in on the dining. Otters in Flaming Gorge have discovered
the salmon in Sheep Creek are pretty easy pickings when they are in
the river to spawn.
Of course, humans also enjoy fishing salmon for dinner. A large
percentage of anglers make the Gorge fishery their destination
specifically because of the salmon.
"40 percent of the anglers in the summer are after kokanee," Mosley
said. State biologists are not sure what the discovery of the whirling
disease spore means to the kokanee population at Flaming Gorge, as
there is not a lot of documented research on the impact the disease
has on salmon.
However, there is another known salmon population infected with
whirling in Utah. Many feared the kokanee in Cache County's Porcupine
Reservoir could be wiped out by whirling disease, but the salmon have
held on at the reservoir. A large number of the salmon in Flaming
Gorge are a result of natural recruitment -- adults spawning and their
offspring surviving. The fish in Sheep Creek contribute only 5 percent
of that recruitment and the rest comes from kokanee that spawn in the
lake. Fish in lakes do not seem as susceptible to the whirling disease
parasite as those in streams and rivers.
Meanwhile, the DWR [Division of Wildlife Resources], in conjunction
with Wyoming Fish and Game, tries to augment the natural population by
stocking between 600 000 and 1.2 million salmon.
One other major concern is downstream from Flaming Gorge. The Green
River, a blue ribbon trout fishery recognized across the world, is now
likely to eventually be diagnosed with the disease.
However, because the majority of fish in the river are brown trout --
which are resilient to the malady -- and the rainbows in the river are
planted from hatcheries, the impact could be minimal.
"Whirling disease has not been the end of everything as many feared
could happen," Mosley said. "We have been pretty fortunate with it.
"Other states have had to deal with major impacts. I'm optimistic we
will make it through this. Hopefully, we don't see any major impacts
in either fishery."
[Byline: Brett Prettyman]
--
Communicated by:
HealthMap Alerts via ProMED-mail
[The state of Utah and Flaming Gorge Reservoir can be located on the
HealthMap/ProMED-mail interactive map at
Photos of kokanee salmon can be seen at
- Sr.Tech.Ed.MJ]
******
[2] Maryland: rainbow trout
Date: Thu 19 May 2011
Source: The Bay Net [edited]
The Maryland Department of Natural Resources (DNR) has confirmed the
presence of whirling disease in a delivery of 8000 commercially
produced rainbow trout stocked in several Western Maryland streams.
These fish are safe to consume, as the disease does not harm humans.
"While we believe this event represents a low risk, DNR considers the
health of Maryland's trout streams and populations a key priority,"
said Fisheries Service Director Tom O'Connell. "Our goal is to
eventually raise all stocked trout within DNR hatcheries. We are
currently developing several new opportunities to expand our hatchery
resources, which will allow us to rigorously monitor and control fish
health issues."
On 11 May 2011, DNR staff observed suspicious behavior in fish that
had been stocked in the North Branch Delayed Harvest Area, Evitts
Creek, Jennings Run, and Sidling Hill Creek. They immediately ceased
stocking activities and took samples for testing. Results of this
sampling confirmed the presence of whirling disease.
The whirling disease parasite was introduced into the eastern United
States from Europe in the late 1950s and is currently known to exist
in 24 states. It was first discovered in Maryland in 1995 in the North
Branch Potomac River. Although harmless to humans, the parasite can be
fatal to trout and is particularly harmful to rainbow trout. DNR is
continuing further testing to investigate this outbreak and working
with the vendor in question to determine why potentially diseased fish may have been delivered. DNR will accept no fish from this vendor
pending the results of this assessment.
DNR established an ongoing disease monitoring program on trout
streams in 2007. Although whirling disease was introduced to several
watersheds in fall 2006, test results have shown that it has not
become established in any areas except the North Branch of the Potomac
River. Regular monitoring and Maryland's past experience and enhanced
understanding of the disease life cycle suggest that the risk of
disease to wild trout populations from this introduction may be low.
However, as a precaution, DNR biologists will conduct additional
disease sampling of adults and sentinel fingerlings over the next
several years.
DNR hatchery resources cannot meet all the demand for stocked trout,
so commercially produced fish are used to supplement spring trout
stocking. Vendors that supply fish to the State are required to be
certified disease free for 3 years. In order to meet spring stocking
goals, DNR is reallocating rigorously tested DNR hatchery produced
fish originally slated for fall stocking.
DNR annually stocks approximately 328 000 fish for the spring trout
season. DNR reminds anglers to help prevent the spread of disease and
invasive organisms by cleaning boots and equipment thoroughly after
fishing. Most importantly, do not move fish from one stream to another
or discard carcasses in streams or on stream banks.
A brochure on whirling disease is available at
--
Communicated by:
ProMED-mail
[The state of Maryland can be located on the HealthMap/ProMED-mail
interactive map at
Photos of rainbow trout can be seen at
and
- Sr.Tech.Ed.MJ]
[Whirling disease affects fish in the trout and salmon [Salmonid]
family. By damaging cartilage, whirling disease can kill young fish
directly, or cause infected fish to swim in an uncontrolled whirling
motion. This can make it impossible for them to escape predators or to
effectively seek food.
Whirling disease is caused by a microscopic parasite called
_Myxobolus cerebralis_. The parasite was introduced to the United
States from Europe in the 1950s and has spread to many streams across
the country. The whirling disease parasite has been found in wild fish
and fish hatcheries in 25 states.
Once established in a stream, the parasite cannot be eradicated, nor
can its worm host, without significantly damaging the ecosystem.
Whirling disease has no known human health effects. Currently there is
no known treatment for affected fish. However, practice management in
hatcheries can reduce the risk.
The disease does not affect humans, only fish in the trout and salmon
family. The infective stage of the parasite can penetrate human skin
and tissues but it does not survive at a human's natural body
temperature. Therefore the disease is harmless to humans and even if
an infected fish is consumed, it will not affect humans.
The disease can be quite devastating to fish and is a concern for all
when it is found in a body of water. Anglers can help by disinfecting
boats, boots, lines, live-wells, and other equipment prior to arrival
at a new/different body of water.
Portions of this comment were extracted from
[see also: other usa outbreaks
2007
----
Whirling disease, fish - USA (AK) 20070606.1826
Whirling disease, fish - USA (MD) (03) 20070505.1454
Whirling Disease, fish - USA (MD) (02) 20070217.0598
Whirling disease, fish - USA (MD) 20070215.0571
2006
----
Whirling disease, fish - USA (UT) 20061214.3517
Whirling disease, fish - USA (OR): transmission 20061105.3175
2005
----
Whirling disease, fish hatchery - USA (UT) 20050429.1194
2003
----
Whirling disease, trout - USA (Wyoming) 20030228.0495
2002
----
Whirling disease, trout - USA (Montana) 20021012.5534
Whirling disease, trout - USA (Utah) 20020711.4724
Whirling disease, trout - USA: resistance 20020326.3820
2001
----
Whirling disease, trout - USA (Utah) 20010209.0263
Whirling disease, trout - USA (Wyoming) 20010105.0041
2000
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Whirling disease, trout - USA (New York) 20001122.2028
Whirling disease, trout hatchery - USA (Wyoming) (02) 20000605.0902
Whirling disease, trout hatcheries - USA (Wyoming) 20000517.0774
Whirling disease, trout - USA (Utah) 20000421.0592
Whirling disease - USA (New Mexico) 20000117.0063]
.................................................sb/tg/mj/jw
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