Identifying global biosecurity hotspots for the amphibian pathogen Batrachochytrium salamandrivorans (Bsal) to inform border surveillance and trade policies

The emerging fungal pathogen Batrachochytrium salamandrivorans (Bsal) poses a severe threat to global amphibian diversity. As a transboundary disease, its spread is primarily facilitated by human activities, notably the international wildlife trade. Preventing its establishment in naive regions is a critical biosecurity priority, which requires a clear understanding of global risk patterns and key introduction pathways. Following the integration of global Bsal occurrence data, environmental variables, and host density data for spatiotemporal cluster analysis, a maximum entropy (MaxEnt) model was employed to map global Bsal suitability and identify high-risk areas. The model’s drivers were analysed to identify key risk factors. The analysis revealed five significant spatiotemporal clusters of Bsal, centred in Germany, the Netherlands, and Belgium. The model identified host density and temperature as the most critical factors determining Bsal suitability. High-risk regions were predicted across Europe, Asia, and North America, aligning with both documented outbreaks (e.g. Belgium and the Netherlands) and major trade hubs like the United States and Canada. Southeast Asia and Central and Southern Europe were identified as particularly vulnerable biosecurity hotspots. This study provides a global biosecurity risk map for Bsal, explicitly linking high-risk zones with international trade and movement pathways. Targeted surveillance at borders, stricter health certifications for amphibians exported from predicted hotspots, and raised public awareness in these regions are recommended. These findings provide a scientific foundation for proactive international policies to mitigate the transboundary spread of Bsal.