Document ID: chunk:federal_register_of_legislation:F2016L01397:body:0:p7
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et al. 2007). Individual frogs contract the disease via contact with infected animals or contaminated water containing spores from infected animals (DSEWPaC, 2013).
Chytridiomycosis mostly affects amphibian species that are associated with permanent water (streams, moist bogs, soaks and ponds). The disease is strongly mitigated by high temperatures, and disease outbreaks tend to occur seasonally (Woodhams and Alford, 2005). However, much is still unknown about the fungus and the disease in the wild, including reasons for the death of hosts, how the fungus survives in the absence of amphibian populations and how it spreads (DSEWPaC, 2013). The fungus can infect freshwater crayfish in North America and this could be a mechanism for its spread and maintenance where amphibians are no longer present (McMahon et al., 2012).
Interactions between the fungus and environmental factors are known to be important. For example, Australian upland populations of frogs have experienced the greatest number of declines and extinctions, leading to the suggestion that the cooler environmental and climatic conditions are more favourable for the growth and persistence of B. dendrobatidis (Scheele et al., 2014).  Amphibian immune systems may be compromised at low temperatures, and other stressors such as chemicals/pesticides or habitat destruction and disturbance could have synergistic effects on disease outcomes and species persistence at a regional level (Buck et al., 2015).
The fungus invades the surface layers of the frog's skin, causing damage to the outer keratin layer. Amphibian skin is unique because it is physiologically active, allowing the skin to tightly regulate respiration, water, and electrolytes. The fungus kills amphibians by disrupting the normal function of the skin resulting in electrolyte depletion and osmotic imbalance (Voyles et al., 2009). In some cases, this appears to cause suppression of the nervous system of the animal and breathing starts to slow down; death occurs when the nervous system reaches a point of paralysis and breathing and the heartbeat stops. Physical signs of paralysis can affect the nervous system as the disease progresses and in some individuals, the toes are curled and the head is tilted sharply forward by the time of death.
In some frog populations, the disease causes 100 per cent mortality, while in other populations, it causes very few deaths. Further, some amphibian species appear to be highly susceptible and die quickly, whilst others seem to be less susceptible (Kriger and Hero, 2006). With antifungal and supportive treatment, infected adult frogs and tadpoles in captive populations can fully recover from the disease.

Of note, the situation in Western Australia is quite different to the eastern states; although chytrid fungus is present in the majority of south-western Australian frog species, the impacts on these species have been non-catastrophic and stable populations persist. At