Alternative Cure Identified for Amphibians with Chytrid Fungus

In a breakthrough finding, researchers have come up with an alternative to the toxic therapy that protects frogs in zoo from the chytrid fungus, a potentially deadly fungal infection.

Globally, the amphibian population is threatened with a fungal disease called chytridionycosis. Frogs  in the wild cannot be protected from this fungal disease but those kept in zoos are given  a toxic itraconzole that helps eradicate the disease when acquired. 

In the current study, researchers at Vanderbilt University found that the use of Chloramphenicol, an antibiotic used to treat serious bacterial infections, does trigger potential changes in the microbes inhabiting the amphibians.

'At risk amphibians' are protected by acquiring the 'founding population' of species that are threatened by chytridiomycosis, a serious infection caused by fungus Batrachochytrium dendrobatidis.

One such of example of the amphibian population that is nearly extinct in the wild but thriving in zoos is the Panamanian Golden Frog.  Zoo and other facilities that have a large number of amphibian species require safe treatments to protect their valuable colonies.

According to Brian Gratwicke, a conservation biologist with the National Zoo, protecting the amphibians in zoos has its own challenges. Initially, the creature must undergo 10 days of immersion in an intraconazole 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 current study, the researchers evaluated two potential alternatives mainly chloramphenicol and amophotericin B.  On using these alternatives, the researchers saw that both the drugs succeeded in lowering the infection caused by B.dendrobatidis, but neither was capable of eradicating it completely. But they found that the drug amphotericin B had an edge over chloramphenicol, as this drug triggered a massive change in the microbe community thriving on the amphibian skin, whereas amphotericin B did not.

A study conducted earlier showed that when the community of microbes on the amphibian skin is left altered or is reduced, the amphibian is more vulnerable to the chytidiomycosis infection. 

Apart from this, amphotericin B is less toxic to the frog when compared to itraconazole. 

Rollins-Smith says, "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."

Chytridiomycosis is a skin disease that causes reduced appetite, weight loss, lethargy and loss of restoring reflex. This often leads to mortality of the amphibian. B. dendrobatidis was first identified in 1998 as a threat to amphibians.

Worldwide there are nearly 7,000 amphibian species including 6,000 frogs, 600-700 salamanders and 200 caecilians.  The IUCN lists nearly 122 species of frogs on its red list, which are more likely to be extinct.

The finding was documented in Applied and Environmental Microbiology.