Distribution and risk factors for spread of amphibian chytrid fungus Batrachochytrium dendrobatidis in the Tasmanian Wilderness World Heritage Area, Australia

Abstract

Chytridiomycosis is an emerging infectious disease caused by the pathogen Batrachochytrium dendrobatidis (Bd) and is the cause of the decline and extinction of amphibian species throughout the world. We surveyed the distribution of Bd within and around the Tasmanian Wilderness World Heritage Area (TWWHA), a 1.38 million ha area of significant fauna conservation value, which provides the majority of habitat for Tasmania's 3 endemic frog species (Litoria burrowsae, Bryobatrachus nimbus and Crinia tasmaniensis). Bd was detected at only 1 (3%) of the 33 sites surveyed within the TWWHA and at 15 (52%) of the 29 sites surveyed surrounding the TWWHA. The relatively low incidence of the disease within the TWWHA suggests that the majority of the TWWHA is currently free of the pathogen despite the fact that the region provides what appears to be optimal conditions for the persistence of Bd. For all survey sites within and around the TWWHA, the presence of Bd was strongly associated with the presence of gravel roads, forest and <1000 m altitude-factors that in this study were associated with human-disturbed landscapes around the TWWHA. Conversely, the presence of walking tracks was strongly associated with the absence of Bd, suggesting an association of absence with relatively remote locations. The wide distribution of Bd in areas of Tasmania with high levels of human disturbance and its very limited occurrence in remote wilderness areas suggests that anthropogenic activities may facilitate the dissemination of the pathogen on a landscape scale in Tasmania. Because the majority of the TWWHA is not readily accessible and appears to be largely free of Bd, and because Tasmanian frogs reproduce in ponds rather than streams, it may be feasible to control the spread of the disease in the TWWHA.

Land-Use Change and Emerging Infectious Disease on an Island Continent

“…This is less problematical for proximal or near-proximal associations. For example, the (introduced) amphibian chytridmycosis pathogen has been shown to be spread into pristine areas by dirt road construction and maintenance in Tasmanian Wilderness World Heritage Area [60]. Hydatids, an important rural zoonoses (sheep-dog cycles) is increasingly recognised in Perth, W.A.…”

Linking Ecology and Epidemiology to Understand Predictors of Multi-Host Responses to an Emerging Pathogen, the Amphibian Chytrid Fungus

“…Several studies highlight a disconnect between predicted environmental suitability for Bd ( i . e ., risk of host exposure) and the detection of population level declines due to the fungus [27–28] suggesting that risk of negative population-level outcomes is also largely dependent on intrinsically-mediated host traits such the ability to tolerate or resist Bd [29–32]. …”

Controlling wildlife fungal disease spread: in vitro efficacy of disinfectants against Batrachochytrium dendrobatidis and Mucor amphibiorum

“…Saprobic growth is suspected but has not been proven. In Tasmania the large southwestern World Heritage Area, which contains 3 endemic frog species (Driessen & Mallick 2003), appears to be largely free from Bd, while it occurs throughout much of the rest of the state (Obendorf & Dalton 2006, Pauza et al 2010.…”

“…Saprobic growth is suspected but has not been proven. In Tasmania the large southwestern World Heritage Area, which contains 3 endemic frog species (Driessen & Mallick 2003), appears to be largely free from Bd, while it occurs throughout much of the rest of the state (Obendorf & Dalton 2006, Pauza et al 2010.In Australia, the introduced plant disease 'Phytophthora root rot' or 'wildflower die-back' caused by the zoosporic oomycete Pc, is widespread and is threatening a number of plant species and commu nities (Rudman 2005). It is of special concern in Tasmanian heathlands, dry forests and buttongrass moorlands.…”