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American Veterinary
Medical Association April 15,2009-Efforts are under way to protect
captive amphibians from a deadly fungus threatening numerous endangered
species.
The chytrid fungus,
discovered in the mid-1990s and associated with declines in amphibian
populations worldwide, notably in Central America and Australia, is
spreading quickly in the wild - most likely as a consequence of human
activity.
In February, 25 of the
world's leading amphibian veterinarians, disease researchers, and
husbandry specialists gathered at San Diego Zoo for a three-day conference
to write a comprehensive manual for controlling and combating diseases in
amphibian survival assurance colonies. Survival assurance colonies have
been formed in zoos throughout the world to preserve amphibian species
that are rapidly facing extinction.
The assembled experts hope
not only to safeguard amphibian collections from chytrid and other
pathogens but also to preserve rare and endangered frogs so that they may
one day be released into their native habitats.
Chytrid fungal disease
causes the infected amphibian's skin to thicken, interfering with its
ability to absorb water and electrolytes. When the fungus spreads to an
area with a highly susceptible species, the results are devastating,
according to Dr. Allan P. Pessier, a veterinary pathologist and researcher
at the San Diego Zoo.
"There's actually good
documented evidence that chytrid fungus will move into a naive population
of frogs and quickly result in this horrific picture of wiping out these
local populations," Dr. Pessier said.
Amphibians in the wild
already are in danger of extinction, attributable to any number of
factors, including habitat loss, the pet trade, and climate change. The
current global decline in amphibians is being compared in magnitude to the
extinction rate of the dinosaurs, according to Dr. Pessier.
Zoo Atlanta's curator of
herpetology, Joseph R. Mendelson, PhD, said dozens of frog species have
already vanished because of chytrid. In environments where the fungus
thrives, it can kill 80 percent of the native amphibians within months,
according to Dr. Mendelson, who added that, in the wild, chytrid is
unstoppable and untreatable.
"Chytrid fungus is
doing things that diseases don't normally do; namely, it's driving species
directly to extinction. That doesn't happen in a normal, healthy
world," he said.
The first known record of
chytrid infection in frogs was in the African clawed frog, which is
commonly sold in pet stores and used for research worldwide.
Chytrid is a sporadic
problem in U.S. zoo collections and is also a concern for species
reintroduction programs because of the potential to release infected frogs
back into the wild, according to Dr. Pessier.
For these reasons, the San
Diego Zoo and Zoo Atlanta, with financial support from the Institute of
Museum and Library Services, brought together amphibian specialists from
the United States, United Kingdom, and Australia to codify disease control
protocols for captive amphibians.
Included in the manual is
information on setting up a biosecure amphibian facility, diagnosing and
treating chytrid fungus in a collection, and disease screening necessary
to release healthy animals back in the wild. The manual, which will be
provided free of charge, is currently being edited and will be reviewed
prior to its anticipated release in fall 2009.
In addition, the grant from
the Institute of Museum and Library Services has made it possible for the
San Diego Zoo to offer the nation's zoos and aquariums low-cost diagnostic
testing for amphibian diseases. Additional laboratory staff have been
hired, and testing is already under way, Dr. Pessier said
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