Batrachochytrium salamandrivorans’ Amphibian Host Species and Invasion Range

Abstract

Batrachochytrium salamandrivorans (Bsal), a species related to the destructive pathogen Batrachochytrium dendrobatidis (Bd), was found and identified in Europe in 2013. Now, a decade later, a large amount of information is available. This includes data from studies in the field, reports of infection in captive amphibians, laboratory studies testing host susceptibility, and data from prospective studies that test for Bsal’s presence in a location. We conducted a systematic review of the published literature and compiled a dataset of Bsal tests. We identified 67 species that have been reported positive for Bsal, 20 of which have a threatened conservation status. The distribution of species that have been found with infection encompasses 69 countries, highlighting the potential threat that Bsal poses. We point out where surveillance to detect Bsal have taken place and highlight areas that have not been well monitored. The large number of host species belonging to the families Plethodontidae and Salamandridae suggests a taxonomic pattern of susceptibility. Our results provide insight into the risk posed by Bsal and identifies vulnerable species and areas where surveillance is needed to fill existing knowledge gaps.

Ecological Barriers for an Amphibian Pathogen: A Narrow Ecological Niche for Batrachochytrium salamandrivorans in an Asian Chytrid Hotspot

“…Despite our extensive sampling of 1101 individuals across 36 species, Bsal was not detected. This absence contrasts with the detection of Bd , which was present in 51 individuals from 16 amphibian species, including the Chinese giant salamander A. davidianus, known to be susceptible to both pathogens [ 10 , 45 , 73 ]. This differential distribution may indicate that these pathogens have distinct ecological niches, potentially driven by differences in their biotic or abiotic preferences.…”

“…It is important to note that the sample size for tested caudates in the study is relatively small—only 30 individuals from 3 species out of a total of 1101 samples representing 36 amphibian species. This is particularly noteworthy given that salamanders are documented to be the most susceptible to Bsal [ 10 , 18 , 22 ]. To this end, extending the range of sampling efforts in environmental reservoirs and salamanders could enrich our understanding of the existence of Bsal .…”

“…Bd affects all three amphibian orders and has caused widespread population declines, particularly in anuran species across all amphibian-inhabited continents, and except in Asia [ 4 , 7 , 8 ]. In contrast, Bsal mainly affects caudates and several anurans [ 9 , 10 ]. It has led to severe declines in native salamanders only in Europe so far, although the pathogen is present in Asia [ 4 , 5 , 6 , 11 ]; however, the impending threat for the highly diverse North American and Neotropical salamanders is significant [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

The amphibian immune system

“…In urodeles, Bsal outbreaks are particularly devastating in East Asia and Europe, while to date Bsal has not been detected in the American continent (reviewed in [130,131]). Very little is known about host immune response against Bsal.…”

Climate as a gatekeeper: Unexpected absence of Batrachochytrium salamandrivoran in an Asian Chytrid hotspot suggests a narrow climatic niche for Batrachochytrium salamandrivorans

“…Bsal has stronger pathogenicity compared to Bd within a shared host species, leading to more severe infection outcomes (Farrer et al, 2017). Out of documented 67 susceptible host species for Bsal , nearly 32 species also can be infected by Bd (Castro Monzon et al, 2023;Olson et al, 2021), these shared species could serve as the hyper-reservoirs or gain greater impacts from both pathogens. Importantly, Bd -Bsal coinfections have been reported in three urodelean species in natural habitats (Lötters et al, 2020;Lötters et al, 2018), and such coinfections are known to increase infection severity and disease risk under the laboratory experimental conditions (Longo et al, 2019;Ribas et al, 2022).…”