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Potensi obat
untuk captive amfibi dengan jamur chytrid
Potential cure for captive amphibians with chytrid fungus
Date:
May 12, 2014
Source:
American Society for Microbiology
Summary:
Researchers have identified an alternative to a
sometimes toxic therapy that protects frogs in zoos from a deadly fungal
infection that has been destroying the amphibian populations worldwide.
..............................
Researchers at Vanderbilt University have identified an
alternative to a sometimes toxic therapy that protects frogs in zoos from a
deadly fungal infection that has been destroying the amphibian populations
worldwide. Their research is published ahead of print in Applied and Environmental
Microbiology.
The fungal
disease, chytridiomycosis, has been decimating frogs all over the world. At
present, nothing can help amphibians in the wild, but zoos currently rely on
the often-toxic itraconazole to eradicate the disease from infected amphibians
they wish to acquire.
To preserve
the most at risk amphibians, zoos have been acquiring "founding
populations" of species threatened by chytridiomycosis, which is caused by
the fungus, Batrachochytrium dendrobatidis.
"Some
species, such as the Panamanian Golden Frog, are nearly extinct in nature, and
doing well only in zoos," says Louise Rollins-Smith, a researcher on the
study. "Facilities which house multiple amphibian species need safe
treatments to protect their valuable colonies."
Brian
Gratwicke, a conservation biologist with the National Zoo, describes the
difficulties zoos face in treating the creatures. The animals must go through
10 days of immersion in an itraconazole solution.
"Itraconazole
is a fairly expensive drug, and depending on the species we treat we can see a
very high mortality rate," says Gratwicke. "An alternative treatment
would be very helpful."
In the study,
Rollins-Smith and colleagues, of Vanderbilt University, Nashville, TN, tested
two potential alternatives, chloramphenicol, and amphotericin B. Although both
drugs reduced B. dendrobatidis infection, neither could eradicate it.
But amphotericin B had a critical advantage over chloramphenicol.
The
investigators found that chloramphenicol can cause major changes in the
community of microbes inhabiting amphibian skin, while amphotericin B does not,
says Rollins-Smith.
Previous
research has shown that altering or reducing the skin microbiome leaves
amphibians more vulnerable to chytridiomycosis infection, she says. Whether by
competing for space, or by providing antimicrobial compounds, the skin
microbiome is probably protective.
Moreover,
amphotericin B is much less toxic to frogs than is itraconazole.
Rollins-Smith
suggests that a more benign cure for chytridiomycosis might involve treatment
first with amphotericin B, followed by itraconazole, which would enable a
lower, less toxic dosing with the latter.
"That
makes sense," says Gratwicke. "It would also correspond with my field
observations."
Chytridiomycosis
is a skin disease. Clinical signs include reduced appetite, weight loss,
lethargy, and loss of righting reflex. Death is thought to result from disruption
of sodium and potassium ion transport in the skin, resulting in osmotic
imbalance and asystolic cardiac arrest.
Gratwicke
and others hope eventually to be able to cure chytridiomycosis with probiotic
treatments that would add protective bacteria to the skin. But such efforts
have yet to bear fruit. B. dendrobatidis was first identified as a
threat to amphibians in 1998.
There are
about 7,000 amphibian species in the world, including roughly 6,000 frogs,
600-700 salamanders, and about 200 caecilians, says Gratwicke. The
International Union for Conservation of Nature lists 122 "missing"
species of frog, on its "red list," most of which are likely extinct,
including 90 for which chytridiomycosis is listed as the essential threat. Some
salamanders and caecilians are also endangered. (Caecilians are legless
borrowing creatures that look like the progeny of a mating between a snake and
a worm).
Story
Source:
The above
story is based on materials provided by American Society for Microbiology. Note:
Materials may be edited for content and length.
Journal
Reference:
- W. M. Holden, A. R. Ebert, P. F. Canning, L. A. Rollins-Smith. Evaluation of amphotericin B and chloramphenicol as alternative drugs for treatment of chytridiomycosis and their impacts on innate skin defenses. Applied and Environmental Microbiology, 2014; DOI: 10.1128/AEM.04171-13
Cite This
Page:
American Society for Microbiology.
"Potential cure for captive amphibians with chytrid fungus." ScienceDaily.
ScienceDaily, 12 May 2014.
<www.sciencedaily.com/releases/2014/05/140512155314.htm>.