Nature conservation

Threatened species

Infection of frogs by amphibian chytrid causing the disease chytridiomycosis



Description

*****NOTE: THIS IS A DRAFT STRATEGY***** Chytridiomycosis is a fatal disease of amphibians and is caused by the chytrid fungus Batrachochytrium dendrobatidis. Chytridiomycosis is a global epidemic and is potentially fatal to all native species of amphibian. Stream-associated frog species and populations at high altitude (>400m) are more likely to be susceptible to the disease. The infection requires water or direct contact between frogs to spread, and its virulence appears sensitive to temperature. Fifty species of Australian frogs have been found infected with the chytrid fungus.

Biodiversity values impacted

Chytridiomycosis has the potential to impact all amphibian species occurring in NSW, including up to 26 threatened frogs. Impacted populations have generally been reported in and to the east of the Great Dividing Range, across all latitudes. The severity of impact on population dynamics varies between species and locations, but has the potential to cause local extinction.

Strategy objective

To prevent the spread of chytrid between amphibian populations and minimise the impacts of infection on susceptible populations across NSW, and to improve understanding of the disease’s dynamics and how they interact with amphibian physiology, genetics and population dynamics, with a view to enhancing immunity.

Priority actions for this KTP

Research

Action DescriptionScale
Develop and improve the application of assisted reproductive technologies to improve outcomes from captive breeding programs.State
Test reintroduction of individuals from potentially resistant populations into sites where the species is known to have occurred previously, or susceptible individuals into sites where chytrid and/or host species (e.g. common eastern froglet) are absent. Monitor reintroduced populations closely with respect to chytrid infection and demographics to better understand the dynamics of both.Site
Using molecular techniques, investigate genetic variation in immune and susceptible species/populations to identify genes that code for disease resistance. Explore methods for increasing resistance genes in populations via selective breeding, gene transfer or genomic selection.State
Implement adaptive management of particular populations to identify environmental drivers of chytrid infection and test methods for reducing risk and maintaining population viability. This includes improving understanding of how chytrid interacts with other threats and environmental processes (e.g. habitat disturbance, climate change, and invasive species such as trout and gambusia) to inform management that will increase population resilience. Also, aim to improve understanding of the reasons why particular amphibian populations are able to persist with fewer demographic impacts at particular locations, in order to apply those learnings to susceptible populations.Site

Prevention

Action DescriptionScale
Enhance and support the ability of existing biosecurity and surveillance measures to detect new strains of chytrid or other pathogens entering Australia (NSW in particular). Develop appropriate communication protocols and a management plan to be triggered in response to the detection of new amphibian pathogens or disease outbreaks in NSW.State

Containment

Action DescriptionScale
No critical actions have been identified under a containment response as chytrid is common in NSW and cannot be contained to a specific location.State

Strategic

Action DescriptionScale
Identify key entry points to sites where important susceptible amphibian populations occur and establish disinfecting/wash stations for bushwalkers, researchers and other people entering these sites.Site
Produce guidelines for developers to mitigate spread of chytrid during and following construction activities. The guidelines should include reference to, for example, hygiene protocols for contractors on site, as well as guidance on sensitive design (e.g. avoiding creating standing ponds which may attract known chytrid host species).State
Develop and implement an education campaign targeting frog study groups, photographers and naturalists, to promote the use of proper hygiene protocols in the field when handling/photographing frogs, as well as to raise awareness about the potential for damaging important habitat. The campaign should target groups such as the Frog and Tadpole Society (FATS), Frogography, field naturalist groups, and universities (particularly coordinators of undergraduate field trips). Develop supporting resources such as hygiene protocols that are made available and are useful for all relevant stakeholders.State
Establish a gene bank to preserve genetic material (e.g. sperm, eggs, tissue) from multiple cell lines for amphibian species at high risk of extinction due to chytrid. Selection and prioritisation of populations to sample should be informed by relevant phylogenies and population genetic data in order to capture appropriate genetic variation. Develop an appropriate governance framework including physical storage at a national or state institution (e.g. museum) and clear guidance on using material if/when required.State

Distribution of the KTP in NSW

Biodiversity asset protection

The priorities for management of amphibian populations impacted by chytrid are focused on increasing resilience via the abatement of other threatening processes, preventing the spread of chytrid throughout the landscape, maintaining chytrid-free refuges and monitoring the health and demographics of populations. The table below outlines the threatened species strategies that are implementing actions to manage the threat of chytrid at a priority SoS site. The table is not a comprehensive list of all species or sites impacted by the threat in NSW.

Investment prioritisation

Priorities for investment in particular projects under SoS will be determined based on alignment with the critical actions outlined above, as well as their benefit (in terms of meeting SoS objectives) relative to implementation cost, as per the SoS KTP Framework.

Monitoring and evaluation

No monitoring and evaluation information available.

Interaction with other KTPs

Key Threatening ProcessInteraction and impacts
Anthropogenic Climate ChangeIt is highly likely that climate change will increase future chytrid impacts in some areas, whilst reducing them elsewhere. Protection of climate refuges, where environmental conditions prevent disease outbreaks can therefore assist some species. Functional trait models have the potential to inform where microhabitat manipulations might be adopted to reduce chytrid transmission under future climate scenarios.
Invasion and establishment of the Cane Toad (Bufo marinus)The effect of chytrid on toads and the role of toads in amplifying or spreading chytrid is uncertain but is probably not important in most areas. This is because 1) adult toads are rarely infected in the wild and 2) although in the lab tadpoles and metamorphs can be infected and metamorphs die with heavy infections, natural toad breeding sites are generally too warm for the fungus. However, in the colder parts of the toad range there are potential impacts.

How will this species be managed?

Key management sites for this threatened species are being identified by the NSW Government and other program partners, where feasible, cost-effective and beneficial management actions can be undertaken. Currently, no management sites have been identified for this threatened species.

  • Identify whether individuals from populations differing in degree of population recovery exhibit corresponding variation in their degree of susceptibility/resistance to infection in a controlled laboratory environment.
  • Identify the degree of variation between populations in terms of underlying natural genetic drift.
  • Identify specific immune mechanisms occurring throughout active infection, comparing this with both control (unexposed frogs) and between source populations for any major observed differences.
  • Characterise key genes involved in the immune response and compare allelic diversity between populations for these key immune genes.
  • Identify whether any allelic diversity identified is associated with directional (positive) selection that could be consistent with the evolution of resistance to chytridiomycosis.