Assessing the spatiotemporal distribution of bufonid herpesvirus 1 (BfHV1) in Europe.

Adverting biodiversity loss is one of the most urgent challenges of our time. The ongoing amphibian extinction crisis is the result of a multitude of factors, with emerging infectious diseases having played a key role. While extensive contributions have been made to study chytrid fungi and ranaviruses in the last two decades, other amphibian pathogens have remained largely unstudied. Here, we evaluated the spatiotemporal distribution of Bufonid herpesvirus 1 (BfHV1) in Europe, a pathogen capable infecting true toads (family Bufonidae). Using molecular detection and histology, we identified seven new BfHV1 positive sites in Germany and a first record for Luxembourg. Phylogenetic analysis of samples from these sites revealed a monophyletic cluster with the known BfHV1 reference sequences. Through additional systematic examination of photographic records from citizen scientists, we identified 229 BfHV1 cases (62 positive, 167 suspicious) in the genus Bufo (B. bufo, B. spinosus), with suspicious cases being widespread across Europe and dating back until at least 2007. As such, this first continental assessment suggests that BfHV1 has been rather overlooked than being recently emerging. Yet, in view of increasing observations of population declines in bufonids across Europe, additional research is warranted to assess its effects on amphibian populations.