What is chytrid fungus?
A healthy Tasmanian tree frog
copyright: Iain Stych
Chytrid (pronounced kit-rid) fungus (Batrachochytrium dendrobatidis
) causes the disease known as chytridiomycosis or chytrid infection which currently threatens Tasmania's native amphibians. The fungus infects the skin of frogs destroying its structure and function, and can ultimately cause death. Sporadic deaths occur in some frog populations, and 100 per cent mortality occurs in other populations.
Chytrid infection has been devastating to frog species causing extinctions worldwide. The international trade of frogs probably brought the fungus to Australia from Africa. The disease has now been recorded in four regions in Australia - the east coast, southwest Western Australia, Adelaide, and more recently Tasmania. In mainland Australia chytrid has caused the extinction of one frog species, and has been associated with the extinction of three other species. In addition, the threatened species status of others frogs has worsened through severe declines in numbers.
What is the threat to Tasmanian frogs?
Tasmania supports 11 frog species
with three of these species, the Tasmanian Tree Frog, the Tasmanian Froglet and the Moss Froglet, found nowhere else in the world. These precious species are at risk from the disease. In addition, two other frog species, the Green and Golden Frog and the Striped Marsh Frog, are already threatened in Tasmania. Chytrid infection has the potential to devastate these, and other frog populations.
What does an infected frog look like?
Great Barred Frog from Queensland with chytrid infection
copyright: Lee Berger
- Abnormal posture and behaviour. Frogs may sit with their hind legs out, wobble or show difficulty moving or fleeing, or may even have a seizure.
- Skin changes. The skin may be discoloured, peel, or possibly ulcerated. The body may swell.
- Sudden death.
- Tadpoles may demonstrate abnormal mouthparts. These abnormalities are difficult to detect and require expertise.
How is it spread?
The movement of infected frogs, tadpoles and water are the known key agents of spread. The fungus (or infected frogs or tadpoles) can be spread by people in water and mud on boots, camping equipment and vehicle tyres, and in water used for drinking, or spraying on gravel roads or fighting fires.
Where is chytrid in Tasmania?
In Tasmania, chytrid infection has spread widely in habitats associated with human disturbance and will continue to spread unless we act quickly. Once established, it is extremely difficult to eradicate chytrid fungus from the natural environment. Remote areas in Tasmania, particularly the Tasmanian Wilderness World Heritage Area, are still largely free of disease and it is our challenge to keep it out.
Photo: RPDC, State of the Environment Tasmania 2008
Click on the map for a larger view
What is being done?
The distribution of chytrid fungus in Tasmania
has been mapped by DPIPWE and the Central North Field Naturalists. Ongoing monitoring of important areas is being conducted by DPIPWE. Our increasing knowledge of this important disease is crucial if we are to effectively reduce fungal spread to uninfected frog habitat.
The National Chytrid Threat Abatement Plan
aims to prevent further spread of chytrid fungus in Australia, and to decrease the impact of the fungus on currently infected populations.
DPIPWE supports the national threat abatement plan in the recently produced strategy
for managing wildlife disease in the Tasmanian Wilderness World Heritage Area. Chytrid fungal disease is the top priority in the Strategy and a number of management actions are being undertaken. In addition, the Wildlife Health in Tasmania Manual
describes chytrid infection in more detail.
Land management agencies are reviewing their practices to determine activities that have potential to spread chytrid fungus and ways to minimise the spread.
Is there any effective treatment?
To date there is no effective way to effectively treat wild infected frog populations. The main aim of management is to prevent further spread of chytrid fungus from infected to uninfected sites.
Chytrid fungus is killed by effective cleaning and drying. In addition, a number of disinfectants are effective.
Recent New Zealand based research
may prove useful in treating infected captive frogs. A range of other treatments may prove effective as well.
What to consider when collecting and reporting tadpoles and frogs
- If it is necessary to collect tadpoles or frogs, always return them to the collection site. Contact DPIPWE on (03) 6165 4305 for information relating to frog collection and permits. Never move frogs or tadpoles to new locations.
- Remember it is an offence to take or disturb frogs and tadpoles in Tasmania's national parks and other reserves without a permit. It is also an offence to bring frogs or tadpoles into reserves.
- Never release frogs found in imported fresh produce (usually banana boxes) and nursery products. Report non-Tasmanian frogs for collection to Biodiversity Conservation Branch, DPIPWE on (03) 6165 4305.
- Report sightings of sick or dead frogs to Biodiversity Conservation Branch, DPIPWE on (03) 6165 4305.
What you can do to stop the spread of chytrid
- Keep your gear clean - clean boots and camping equipment of soil and allow to dry completely before visiting remote areas.
- Plan to wash and dry vehicles (including tyres) and equipment before entering dirt roads within areas that are reserved or largely free of human disturbance.
- Think about water disposal - when disposing of small or large volumes of water within a natural environment, ensure you are as far as possible from creeks, rivers, ponds and lakes. A dry stony disposal site is far preferable to a moist muddy one.
- Avoid transferring aquatic plants, water, soils and animals between frog habitats (for example, nursery plants, wet land fill and fish).
- Education in relation to disease management is critical if we are to stop the spread of this important disease. Spread the word!