Tracking Batrachochytrium dendrobatidis Infection Across the Globe

Abstract

Infection records of Batrachochytrium dendrobatidis (Bd), a pathogen that has devastated amphibian populations worldwide, have rapidly increased since the pathogen’s discovery. Dealing with so many records makes it difficult to (a) know where, when and in which species infections have been detected, (b) understand how widespread and pervasive Bd is and (c) prioritize study and management areas. We conducted a systematic review of papers and compiled a database with Bd infection records. Our dataset covers 71 amphibian families and 119 countries. The data revealed how widespread and adaptable Bd is, being able to infect over 50% of all tested amphibian species, with over 1000 confirmed host species and being present in 86 countries. The distribution of infected species is uneven among and within countries. Areas where the distributions of many infected species overlap are readily visible; these are regions where Bd likely develops well. Conversely, areas where the distributions of species that tested negative overlap, such as the Atlantic Coast in the USA, suggest the presence of Bd refuges. Finally, we report how the number of tested and infected species has changed through time, and provide a list of oldest detection records per country.

Global Patterns of the Fungal Pathogen Batrachochytrium dendrobatidis Support Conservation Urgency

“…Our compilation of Bd sampling shows increasing taxonomic scope of sampled families and species, increased incidence of species infection, and increased geographic occurrence. Below, we combine our findings with those of Castro Monzon et al (30) to yield a more comprehensive tally of total Bd occurrence patterns. In addition, our analyses support emergence of new key climate predictors of Bd occurrence and geographic variance in climate metrics associated with the occurrence of Bd.…”

“…Amphibian diseases span both lethal and sublethal multiple-host species infections by microparasites such as trematodes (21), bacteria (22), fungi (15,23,24), protists (25,26), and viruses (16,24). Information on amphibian disease-causing pathogens has increased substantially in the last two decades, especially relative to field surveillance of taxonomic and geographic patterns of pathogen occurrences at global scales (27)(28)(29)(30)(31) and experimental research that illustrates species-specific vulnerabilities and interacting factors (24,32). Keeping informed about rapid advances in research and monitoring of amphibian diseases is challenging.…”

“…Furthermore, the initial Bd database was not set up to report zoospore loads for samples-these were not being reported in 2007, and even today, not all publications report Bd zoospore loads. Owing to continuing requests for the world Bd database, renewed calls for comprehensive analyses of world-scale data of amphibian disease threat patterns (18), and significantly increasing reports of Bd research and surveillance (24,29,30,32), the global Bd database and web portal warrant maintenance and improved capacity. The new web portal AmphibianDisease.org (41) is developing to enable broader chytrid data reporting (e.g., strains, captive hosts, eDNA, zoospore loads) and user-friendly data import and export functions.…”

“…Lastly, we compare our Bd database tallies by taxon and countries through 2019 with the 2020 results reported by Castro Monzon et al (30) who examined the peer-reviewed literature of Bd occurrences aggregated by a web-search engine. We combine unique taxonomic and country data from Castro Monzon et al (30) with our findings for an overarching summary of the taxonomic and geographic scope of Bd knowledge to date.…”

Long-Term Monitoring of Amphibian Populations of a National Park in Northern Spain Reveals Negative Persisting Effects of Ranavirus, but Not Batrachochytrium dendrobatidis

“…The amphibian chytrid fungus, Batrachochytrium dendrobatidis (hereafter Bd ), is a generalist pathogen that has driven declines and extinctions across a broad range of amphibian host species ( 13 , 14 ). Bd is able to infect over 50% of all tested amphibian species, with over 1,000 confirmed host species in at least 86 countries ( 15 ). Viral infections caused by ranaviruses (hereafter Rv ), an emerging group of pathogens with a host range spanning all ectothermic vertebrates, have also become more prevalent and are increasingly associated with mass amphibian die-offs ( 16 , 17 ).…”