Swabbing Method for Real Time PCR detection of Batrachochytrium dendrobatidis
Chytrid fungus in the Sierra Nevada mountains of California, USA
The purpose of this site is to help inform people about the occurrence and potential spread of a pathogenic chytrid fungus in amphibian populations of the Sierra Nevada.
A chytrid fungus, Batrachochytrium dendrobatidis, causes death in post-metamorphic frogs (Nichols et al. 2001) and infects the keratinized mouthparts of tadpoles. It has been implicated in amphibian declines in Australia, the Neotropics, North America, and in Europe (Berger et al. 1998; Bosch et al. 2001; Bradley et al. 2002). This fungus has recently been discovered in amphibians in California including several species in the Sierra Nevada (Fellers et al. 2001). For more information on this disease please go to the JCU amphibian diseases home page.
Fellers et al. (2001) found that conspicuous oral disc abnormalities including depigmented tooth rows, depigmenteed jaw sheaths, and swollen labial papillae (along the margins of the oral disc) are strongly associated with Batrachochytrium infection in R. muscosa. However, Rachowicz (2002) found that a lack of pigmentation in R. muscosa tadpole mouthparts is also associated with a seasonal trend in mouthpart pigmentation.
Rachowicz and Vredenburg (2004) distinguished between the patterns of mouthpart loss due to chytridiomycosis versus depigmentation associated with overwintering temperatures (see figure below). Since chytridiomycosis has been found in populations that have undergone declines, we recommend that herpetologists examine tadpole mouthparts and take proper precautions to prevent spread of this disease.
If you see any R.muscosa tadpoles that are lacking black pigmentation in their mouthpart area, please contact Vance Vredenburg (vancev AT sfsu.edu)
Below: illustration of larval Rana muscosa mouthparts showing two patterns of pigment loss over time. Upper (anterior) tooth rows (t), upper and lower (posterior) jaw sheaths (j), and four lower tooth rows (t) are shown. Black is pigmentation and gray is loss of pigment. A-d represents the pattern of loss associated with Batrachochytrium dendrobatidis and e-h represents the pattern of pigment loss associated with a low overwintering temperature. Note that some R. muscosa tadpoles have 1-2 additional tooth rows anterior to the upper jaw sheath. The outline of the tadpole mouthparts is from Altig et al. (1998).
Effects of chytridiomycosis on tadpole mouthparts
Altig, R., McDiarmid, R. W., Nichols, K. A., and Ustach, P. C. 1998 A key to the anuran tadpoles of the United States and Canada. Contemporary Herpetology Information Series 2. U.S. Geological Survey, Patuxent Wildlife Research Center, National Museum of Natural History, Washington, D.C., USA.
Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. 1998. Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. Proceedings of the National Academy of Sciences of the United States of America, 95: 9031-9036.
Bosch, J., Martinez-Solano, I., and Garcia-Paris, M. 2001. Evidence of a chytrid fungus infection involved in the decline of the common midwife toad (Alytes obstetricans) in protected areas of central Spain. Biological Conservation, 97: 331-337.
Bradley, G.A., Rosen, P. C., Svedl, M. J., Jones, J. R., and Longcore, J. E. 2002. Chytridiomycosis in native Arizona frogs. Journal of Wildlife Diseases 38: 206-212.
Fellers, G. M., Green, D. E., and Longcore. J. E. 2001. Oral Chytridiomycosis in Mountain Yellow-Legged Frogs (Rana muscosa). Copeia 2001(4): 945-953.
Nichols, D. K., Lamirande, E. W., Pessier, A. P., and Longcore, J. E. 2001. Experimental transmission of cutaneous chytridiomycosis in dendrobatid frogs. Journal of Wildlife Diseases 37: 1-11.
Rachowicz, L. J. 2002. Mouthpart pigmentation in Rana muscosa tadpoles: seasonal changes without chytridiomycosis. Herpetological Review 33: 263-265.
Rachowicz, L.J. and Vredenburg, V. T. 2004. Transmission of Batrachochytrium dendrobatidis within and between amphibian life stages. Diseases of Aquatic Organisms 61: 75-83.
Vredenburg, V. T., and Summers, A. P. 2001. Field identification of chytridiomycosis in Rana muscosa (Camp 1915). Herpetological Review 32:151-152.