Species Infected

Forty nine species of wild amphibians in Australia have been found infected with the amphibian chytrid, B. dendrobatidis. Since these 49 include the introduced cane toad, Bufo marinus, 48 native species, 22% of the 218 Australian native species, are infected in the wild.

An additional 2 native species that have not been recorded as infected in the wild have been recorded as infected in captivity. Consequently, we know that 50 of the Australian native species can be infected by B. dendrobatidis. The introduced axolotyl, sold commercially in Australia, has also been found to be infected in Townsville (reported by Rick Speare Feb 1999) and in Perth (reported by Ken Aplin June 1999). The "Chytidiomycosis status in Australia" link below gives an overview of infection status by species and state.

Distribution within Australia

In Australia the amphibian chytrid appears to be found in four zones; a large east coast zone extending from north of Cooktown to Melbourne, Tasmania, a zone around Adelaide in South Australia, and a south-west zone extending from Perth over most of the southwest of Western Australia. The Tasmanian infections have been only recently found in late 2004. Northern Territory is the only state or territory with no positive records. Follow the link "Chytridiomycosis by state".

Time of Invasion

B. dendrobatidis is not native to Australia. It probably arrived in southeast Queensland in the mid-1970s on imported specimens of the African clawed frog, Xenopus laevis. However, this is speculative. Our earliest record in Australia is December 1978 in the Connondale Ranges, west of Brisbane and our hypothesis is that the amphibian chytrid fungus escaped from captivity in Brisbane and spread centripetally. Once B. dendrobatidis invades an area, it stays. Epidemiological evidence indicates that the amphibian chytrid fungus spread north and south as an advancing front, colonising frogs and water bodies as the front passed. The rate of advance has been estimated as 100 km / year in coastal Queensland and 20-30 km / year in Central America.

From museum records the estimate of the earliest appearance of B. dendrobatidis in each zone has been obtained; east coast zone - December 1978, southwest zone - October 1985, and Adelaide zone - May 1996. With more extensive retrospective searching, we may be able to establish earlier arrival dates in each zone. We speculate that each zone was initiated by B. dendrobatidis escaping into the wild from an infected amphibian imported from an infected Australian zone or another country.

Impact of the Amphibian Chytrid Fungus in Australia

As the invasive front infected naive amphibian populations, the outcome was determined by an interplay between pathogen, host and environment. Some species of amphibians were exquisitely sensitive to chytridiomycosis, occurred in habitats that favoured virulence and became extinct. Of these, Taudactylus acutirostris, was a species made extinct by B. dendrobatidis; the last population crashed as a result of chytridiomycosis in the upland rainforests of North Queensland in September 1993 and the last known specimen died from chytridiomycosis in captivity at the Melbourne Zoo in 1995. B. dendrobatidis has also been found in 8 endangered and 5 vulnerable species.

The links below are to pages that summarise records of amphibians found infected by B. dendrobatidis in Australia. The source database is maintained by Rick Speare, Amphibian Diseases Ecology Group, James Cook University, Townsville, Australia.

Most diagnoses were made by histological techniques. See Berger L, Speare R, Kent A. Diagnosis of chytridiomycosis in amphibians by histologic examination for the technique. Some diagnoses have been made by examining unstained superficial epithelium under the light microscope, but these are usually confirmed by histology. Recently, diagnoses have been made using PCR. In Australia this is typically the real time PCR developed by AAHL ( Boyle et al 2004).

Page maintained by: Rick Speare Rainforest CRC & School of Public Health and Tropical Medicine James Cook University Townsville 4811 Australia

Please submit new records to Rick Speare ( richard.speare@jcu.edu.au).