Developing effective and sustainable mitigation measures against Bsal infection is critical to the conservation of global amphibian biodiversity. The survival of several endangered and/or Bsal-susceptible amphibian species is dependent on the scientific community’s ability to further investigate Bsal and identify potential sustainable mitigation measures.
Garner et al. (2016) have suggested that a unidimensional mitigation approach is not practical and that a multifaceted line of action is imperative to achieve even a modicum of success. It is further stated that this approach also has to be geared toward the specific stage of emergence of the pathogen. Current mitigation efforts include a combination of preventative measures and short term approaches. However, more lasting and sustainable fixes are required if efficacious solutions to Bsal outbreaks are to be found.
Also a stronger connection between the researchers and managers is needed, for example by increasing the number of applied studies (but not at the expense of fundamental research), in an attempt to more efficaciously mitigate amphibian diseases (Canessa et al., 2019).
Understanding the introduction routes of an emerging pathogen in wild living amphibian populations in Europe is essential in order to set up prevention and mitigation measures. Bsal can be introduced in natural ecosystems in various ways (e.g. by introduction or translocation of amphibians, by contaminated materials, by natural dispersal It is important to anticipate possible Bsal introduction routes and mechanisms in order to mitigate these as much as possible.
The overriding objective is the preservation of urodelan biodiversity, which includes the following objectives:
- minimise the risk of Bsal introduction,
- contain/eradicate the pathogen and
- preserve the affected population.
Bsal has been shown to be endemically present in wild living urodele populations in east Asian countries (Martel et al., 2014; Laking et al., 2017; Beukema et al., 2018; Yuan et al., 2018) with some of these urodele species being heavily traded internationally. Clear links could be established between Bsal positive amphibians collections across Europe, using data of trade events (Fitzpatrick et al., 2018). Most likely, introduction of Bsal has occurred through the international pet trade (Martel et al., 2020). Imposing trade restrictions/bans (EU decision 2018/320) on amphibian trade and performing pre-import screening for Bsal in the live animal trade, screening captive amphibian collections and treating Bsal positive collections in order to eliminate the Bsal reservoir in captive collections (striving for a clean trade) is an essential step in the prevention of Bsal introductions in Bsal free habitats.
In general, actions to prevent the introduction/pathogen establishment/or the further spread of Bsal should target the environment, the host species, and/or the fungus itself.
Prior to and upon introduction of Bsal in amphibian habitats, strict biosecurity measures should be implemented to avoid anthropogenic spread of Bsal in between/into amphibian habitats. Optimal habitat management (to increase amphibians resistance against infections), removal of non-native (potential Bsal carrier species) from the environment and close monitoring of amphibian populations is highly advisable. (Inter)national and regional Early Warning Systems (EWS), to swiftly detect and report disease-/mortality events in amphibian populations across Europe are highly recommended. These EWS allow rapid response measures to be taken after introduction of Bsal has occurred in amphibian populations (Thomas et al., 2018). Everyone can contribute to these EWS by reporting observed disease/mortality to the regional hotlines.
Once Bsal introduction has occurred in a novel naïve site, several mitigation measures have been proposed, focusing on the reduction of the fungal load in the environment and on the host species, through safeguarding amphibian populations to prevent population extirpation (e.g. setting up ex situ amphibian colonies of especially those (sub)species of conservation importance). The prevention of further spread of Bsal in the environment through the application of strict biosecurity measures, creating barriers to contain the Bsal outbreak and halt the Bsal spread is essential.
Suggestions about potential longer-term management actions to mitigate chytridiomycosis are available from: Woodhams et al. (2011), Scheele et al. (2014), Garner et al. (2016), Grant 2016, Canessa et al. (2018), Thomas et al. (2019), Martel et al. (2020).