Arizona Game and Fish Department cautioned traveling anglers and
boaters recently against inadvertently importing a disease that
causes erratic behavior in trout.
Whirling Disease, caused by
Myxobolus cerebralis, is a
microscopic parasite that attacks trout. The disease can result in
high mortality rates among young fish.
"Whirling Disease" is so named because it may cause very young
affected fish to swim in circles. Affected fish often find it
difficult to feed or avoid predators.
There is no known cure for the disease, which attacks the soft
cartilage of younger trout, especially rainbow, cutthroat, and
brook trout. Brown trout and grayling are considered less
The disease has not been documented in Arizona’s two native
trout species, Apache and Gila.
Arizona has been relatively free of Whirling Disease, with only
one outbreak discovered in a private pond, according to the
Whirling Disease Foundation. But, neighboring states have had
substantially higher levels of the disease, and Arizona officials
fear anglers and boaters may inadvertently bring the disease into
Neighboring states California, Nevada, Utah, New Mexico, and
Colorado have all had outbreaks of the disease.
Whirling Disease was first detected in California in 1965 and
is still present in Northern California throughout the Sacramento
River Basin area. The disease was first detected in Nevada in 1966
and is currently established in the Truckee, Carson, Owyhee, East
Walker, and Little Humboldt Rivers as well as regional creeks,
lakes, and reservoirs — including Lake Tahoe.
Whirling Disease was first detected in Utah in 1991 in a
private hatchery. Two state hatcheries and numerous private
facilities have tested positive.
In the wild, the parasite has been detected in the Logan,
Little Bear, Ogden, Weber, Provo, and Beaver rivers as well as
regional creeks, lakes, and reservoirs.
Whirling Disease was discovered in Colorado in 1987 and is now
found in nine state hatcheries, numerous private facilities, and
all coldwater drainages except the Animas and North Republican
rivers, according to the foundation. The disease was first
detected in New Mexico in 1988 in private ponds and currently
infects the Pecos, Cebolla, San Juan, Cimarron, Red, and Canones
rivers as well as three of the state’s seven hatcheries.
Whirling Disease has not been detected in Arizona hatcheries,
and has not been detected in public areas, according to the
Whirling Disease Foundation.
Typical signs of Whirling Disease include darkened tail,
twisted spine, deformed head, and erratic swimming behavior.
Although fish exhibiting these symptoms may have genetic defects
or afflictions other than Whirling Disease, persons observing such
behavior in fish should contact Arizona Game and Fish or Arizona
Department of Agriculture.
In order to avoid inadvertent spreading Whirling Disease, the
foundation requests anglers and boaters use the following
- do not transport live fish from one body of water to
- do not use trout, whitefish, or salmon parts as bait,
- do not dispose fish entrails or skeletal parts in garbage
disposals or near bodies of water, and
- rinse mud and debris from equipment and apparel before
leaving a known Whirling Disease-infected body of water.
To explain why fish waste may not be put down garbage disposals
or dumped near watersheds, the foundation points out that dead,
infected fish may release millions of nearly indestructible spores
that may remain dormant for up to 30 years. Such spores typically
survive most wastewater treatment systems, the foundation states.
The best method to scrub contaminated equipment and apparel is
to soak or spray items with chlorine bleach and water solution.
Depending upon the situation, the bleach and water ratio may vary
between 1:32 to 1:1. Solution soak times range from 10 minutes to
spray and wipe.
For more information contact www.whirling-disease.org.
Whirling Disease is not threat to those who consume fish,
according to a 2001 Arizona Department of Agriculture release.
"Whirling Disease is not transmittable to people," said state
veterinarian Rick Willer. "In fact, trout infected with the
disease are edible."
Arizona Game and Fish Department did not respond to inquiries
made prior to this article’s deadline.