Chytridiomycosis

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Chytridiomycosis is a fatal infectious disease that affects amphibians, caused by the chytrid fungus - Batrachochytrium dendrobatidis (Bd). Chytridiomycosis has caused dramatic population declines or even extinctions in western North America, Central America, South America, and eastern Australia. There is no effective measure for control of the disease in wild populations. The disease is contributing to a worldwide decline in frog populations, a worldwide decline of species that apparently has affected 30% of the amphibian species of the world<ref>Stuart, S. N., J. S. Chanson, et al. (2004). "Status and trends of amphibian declines and extinctions worldwide." Science 306: 1783-1786.</ref>.

Although some declines have been credited to the fungus Batrachochytrium dendrobatidis, there are species that resist the infection and some reports have found that some populations can survive with a low level of persistence of the disease<ref>Retallick, R. W. R., H. McCallum, et al. (2004). "Endemic Infection of the Amphibian Chytrid Fungus in a Frog Community Post-Decline." PLoS Biology 2(11): e351.</ref>. In addition, most of the laboratory studies are not ecologically-relevant, which makes it difficult to take their conclusions to the field.

The first reports of infection of Batrachochytrium are from African clawed frogs of the genus Xenopus. Because Xenopus has been widely transported around the world, it is one potential vector for transmission of Bd. However, other studies suggest that Bd has been present in North and Central America for decades.

Laboratory studies suggest that the fungus performs poorly at high temperatures<ref>Berger, L., R. Speare, et al. (2004). "Effect of season and temperature on mortality in amphibians due to chytridiomycosis." Australian Veterinary Journal 82: 31-36.</ref>, and that exposure of infected frogs to high temperatures will kill the fungus<ref>Woodhams, D. C., R. A. Alford, et al. (2003). "Emerging disease of amphibians cured by elevated body temperature." Diseases of aquatic organisms 55: 65-67.</ref>. This is believed to explain why chytridiomycosis occurs primarily in cool climates.