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Volume 5, Number 6—December 1999


Emerging Infectious Diseases and Amphibian Population Declines

Peter Daszak*Comments to Author , Lee Berger†‡, Andrew A. Cunningham§, Alex D. Hyatt†, D. Earl Green¶, and Rick Speare‡
Author affiliations: *Institute of Ecology, University of Georgia, Athens, Georgia, USA; †Australian Animal Health Laboratory, Commonwealth Scientific Industrial Research Organization, Geelong, Victoria, Australia; ‡School of Public Health and Tropical Medicine, James Cook University, Townsville, Queensland, Australia; §Institute of Zoology, Zoological Society of London, London, United Kingdom; and ¶National Wildlife Health Center, U.S. Geological Survey, Madison, Wisconsin, USA

Main Article

Table 1

Mass deaths caused by chytridiomycosis and ranaviral disease in wild populations of amphibians

Locality and date of mass deaths Species affected and impacta References
Chytridiomycosis E. & S. Australia Multiple montane rain forest and temperate 28-30
(1993-1999)b species. Mass deaths, local extinctions,
population declines. Near-extinction
of Taudactylus acutirostris. Hypothesized
link with global extinction of two species
of gastric brooding frog (Rheobatrachus spp.).
W. Australia Multiple species, predominantly the western 29,31
(1998-1999)c green (or motorbike) frog (Litoria moorei).
Mass deaths, population declines.
Costa Rica Multiple montane rain forest species. 20,23,
and Panama Mass deaths, local extinctions, population 28,29
(1994-99) declines. Hypothesized link with global
extinction of golden toad, Bufo periglenes.
Ecuador (1999) Montane rain forest Atelopus species, Telmatobius 29
niger, and Gastrothecus pseustes. Unknown impact.
Arizona Leopard frog (Rana yavapiensis & 29
(1996-1997) R. chiricahuensis). Mass deaths.
S. Arizona (1999) Leopard frog (Rana sp.). Mass deaths. 31,32
Colorado (1999) Boreal toad (Bufo boreas). Mass deaths. d
Colorado (1970s) Leopard frog (Rana pipiens). Mass deaths. 32d
Sierra Nevada, Yosemite toad (Bufo canorus). Mass deaths. 32e
California (1970s)
Ranaviral disease United Kingdom Common frog (Rana temporaria). Mass deaths, 5,16,26,
(1992-1999f) possibly population declines. 33,34
Arizona (1995) Sonoran tiger salamander (Ambystoma tigrinum 27
stebbinsi). Mass deaths in this endangered species.
N. Dakota (1998) Tiger salamander (A. tigrinum). 35
Mass deaths.
Maine (1998) Tiger salamander (A. maculatum). 35
Mass deaths.
Utah (1998) Tiger salamander (A. tigrinum). Mass deaths. 35
Saskatchewan, Tiger salamander (A. tigrinum diaboli). Mass deaths. 36
Canada (1997)

aMass deaths did not occur in all cases of wild amphibians infected by chytridiomycosis. Bufo americanus from Maryland and Acris crepitans from Illinois have been found infected with chytridiomycosis without observed deaths (37,38). In Australia, chytridiomycosis has been reported from small numbers of amphibians without evidence of clinical signs or deaths in both upland and lowland species (R. Speare, L. Berger, unpubl. obs.).
bRetrospective studies have identified chytridiomycosis as the cause of death in wild frogs in five Australian states from as early as 1989 (29).
cThis recent outbreak was more than 2,000 km from the closest recorded chytridiomycosis-linked amphibian die-offs (31). It is thought that chytridiomycosis may now be enzootic in many areas of Australia, but still in the process of spreading to naïve populations. A role for chytridiomycosis in other recent W. Australian declines is suspected due to similarities in the pattern of declines and presence of the Batrachochytrium carcasses from W. Australia since 1992.
dD.E. Green, unpubl. obs.
eD.E. Green, unpubl. obs. Historically collected specimens recently examined histologically revealed chytridiomycosis as a contributing factor to the cause of death in 2 of 12 animals.

Main Article

1Note that the relative number of mass death events decreases with increasing impact on population.