A. Gordon Brown, DOI Invasive Species Coordinator and Liaison to the National Invasive Species Council

Dr. Jim Tate, Science Advisor to the Secretary

DOI

Batrachochytrium dendrobatidis was first reported in 1998 by Berger et al. (Berger, et al. 1998) and described as a new genus and species in 1999 (Longcore, et al. 1999); although it had been incorrectly identified as another fungus in 1991 (Groff, et al. 1991). This fungus seems to be able to live in the skin of all amphibians and is more or less pathogenic depending on the particular species (Bufo boreas is susceptible) of amphibian, the age at which they are exposed to the pathogen and the temperatures at which the amphibians live. Daszak et al. (Daszak, et al. 1999) considered it an emerging infectious disease and the NSF funded two multi-institutional grants to study amphibian diseases of which chytidiomycosis was one ( with the other being a frog virus. In 2000 a workshop was held in Cairns, Australia to promote knowledge of this species and formulate recommendations to lessen the risk of chytridiomycosis to wild amphibians

The Berger et al paper included information on this chytrid fungus killing amphibians in Australia and Panama, causing declines in populations and possibly extirpating 2 species. Since that time, population declines caused by this fungus have been reported from the Boreal toad in Colorado, the Wyoming toad in Wyoming, the mountain yellow leg frog in the Sierra of California and numerous additional species in Central America. Specific to the Boreal toad in Colorado, because I was the mycologist interested in isolating the fungus to have it available for studies of population genetics—to answer the question of whether this organism was native or introduced—I was the recipient of dead Boreal toads sent by Mark Jones, then the Colorado Fish & Game biologist working on the boreal toad project. I examined the skin of these toads in the process of isolating the fungus and found a very heavy infection of Batrachochytrium dendrobatidis, consistent with the levels I had seen in frogs that had died in controlled experiments from inoculation with Batrachochytrium ((Nichols, et al. 2001).

Does Batrachochytrium kill Bufo boreas in Colorado? Yes, I think it does (Muths, et al. 2003).

Retrospective studies i.e., histological preparation of skin samples from archived museum specimens have revealed no evidence of the fungus in North America prior to 1961 (Ouellet, et al. 2005). The earliest collected museum specimen infected with B. dendrobatidis was collected in South Africa in 1938 (Weldon, et al. 2004) in a Xenopus frog. Xenopus frogs were exported from South Africa to North America beginning in the 1930’s (see Ché Weldon’s PhD thesis, North-West University, Pochefstroom, South Africa 2005) because they were widely used in local hospitals to test for pregnancy. If a woman was pregnant, injecting some of her urine into a female Xenopus laevis frog cased the frog to ovulate. The hypothesis that Batrachochytium originated in Africa and was transported around the world by export of frogs was neither confirmed nor disproved by a study of its population genetics (Morehouse, et al. 2003). Analysis of the data suggest that different isolates from North America, Panama and Australia are part of a recently spread clone, with the definition of recently as being since the breakup of Pangea. In other words, because frogs don’t cross oceans by themselves, this organism was probably spread by the activity of humans. We lack optimum population genetics markers for this organism but expect to learn more about the genetics soon because the entire genome of this organism is being sequenced by two genome sequencing laboratories, the Broad Institute and the DOE Joint Genome Sequencing Institute

Is Batrachochytrium dendrobatidis an invasive organism? Yes, the evidence suggests that it is, although where it originated is still being investigated.

Does Batrachochytrium dendrobatidis move by human activity? Yes, at least in part. For transcontinental distances it moves by human activity. It moves around the United States and other countries by trade in frogs for scientific and culinary purposes (I isolated several of my cultures from a frogs in the scientific trade.) Frogs scheduled to be destroyed after use in a laboratory or schoolrooms are sometimes released (In Arizona and California are feral populations of the African clawed frog). Because some frogs carry this disease without ill effects or noticeable signs, carrier frogs can be released.

Concern about biologists transferring this disease have been sufficient that protocols are in place that herpetologists (most herpetologist, we hope) voluntarily use to thoroughly dry or disinfect their gear between watersheds

Once this organism is in an area, it can spread by non-man mediated means.

Colorado biologists knowledgable about Batrachochytrium and Bufo boreas include Erin Muths, USGS-BRD, Cynthia Carey, U. Colorado, Boulder, Mark Jones, Colorado Fish & Game, Lauren Livo, U. Colorado, Boulder.

Joyce E. Longcore

Department of Biological Sciences

University of Maine

Orono, ME 04469-5722

Telephone: 207-581-4396

Fax: 207-581-2969

Email:

Berger, L., R. Speare, P. Daszak, D. E. Green, A. A. Cunningham, C. L. Goggin, R. Slocombe, M. A. Ragan, A. D. Hyatt, K. R. McDonald, H. B. Hines, K. R. Lips, G. Marantelli and H. Parkes, 1998. Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. Proc. Natl. Acad. Sci. USA 95:9031-9036.

Daszak, P., L. Berger, A. A. Cunningham, A. D. Hyatt, D. E. Green and R. Speare, 1999. Emerging infectious diseases and amphibian population declines. Emerging Infectious Diseases 5:735-748.

Groff, J. M., T. S. Mughannam, A. McDowell, A. Wong, M. J. Dykstra, F. L. Frye and R. P. Hedrick, 1991. An epizootic of cutaneous zygomycosis in culture dwarf African clawed frogs (Hymenochirus curtipes) due to Basidiobolus ranarum. Journal of Medical and Veterinary Mycology 29:215-223.

Longcore, J. E., A. P. Pessier and D. K. Nichols, 1999. Batrachochytrium dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia 91:219-227.

Morehouse, E. A., T. Y. James, A. R. Ganley, R. Vilaglys, L. Berger, P. J. Murphy and J. E. Longcore, 2003. Multilocus sequence typing suggests the chytrid pathogen of amphibians is a recently emerged clone. Molecular Ecology 12:395--403.

Muths, E., P. S. Corn, A. P. Pessier and D. E. Green, 2003. Evidence for disease-related amphibian decline in Colorado. Biological Conservation 110:357-365.

Nichols, D. K., E. W. Lamirande, A. P. Pessier and J. E. Longcore, 2001. Experimental tranmission of cutaneous chytridiomycosis in dendrobatid frogs. Journal of Wildlife Diseases 37:1-11.

Ouellet, M., I. Mikaelian, B. D. Pauli, J. Rodrigues and D. M. Green, 2005. Historical evidence of widespread chytrid infection in North American amphibian populations. Conservation Biology

Weldon, C., L. H. du Preez, A. D. Hyatt, R. Muller and R. Speare, 2004. Origin of the amphibian chytrid fungus. Emerging Infectious Diseases 10:2100-2105.