Batrachochytrium salamandrivorans Threat to the Iberian Urodele Hotspot

Abstract

The recent introduction of the chytrid fungus Batrachochytrium salamandrivorans into northeastern Spain threatens salamander diversity on the Iberian Peninsula. We assessed the current epidemiological situation with extensive field sampling of urodele populations. We then sought to delineate priority regions and identify conservation units for the Iberian Peninsula by estimating the susceptibility of Iberian urodeles using laboratory experiments, evidence from mortality events in nature and captivity and inference from phylogeny. None of the 1395 field samples, collected between 2015 and 2021 were positive for Bsal and no Bsal-associated mortality events were recorded, in contrast to the confirmed occurrence of Bsal outbreak previously described in 2018. We classified five of eleven Iberian urodele species as highly susceptible, predicting elevated mortality and population declines following potential Bsal emergence in the wild, five species as intermediately susceptible with variable disease outcomes and one species as resistant to disease and mortality. We identified the six conservation units (i.e., species or lineages within species) at highest risk and propose priority areas for active disease surveillance and field biosecurity measures. The magnitude of the disease threat identified here emphasizes the need for region-tailored disease abatement plans that couple active disease surveillance to rapid and drastic actions.

New Data on the Larval Stages of Leptophallus nigrovenosus (Digenea, Plagiorchiata)

“…The fungi Batrachochytrium dendrobatidis (Longcore, Pessier, and D.K. Nichols (1999)) and Batrachochytrium salamandrivorans (Martel A., Blooi M., Bossuyt F., Pasmans F. ( 2013)) (Batrachochytriaceae), which produce chytridiomycosis, have been detected in Spain [55], and experimental studies have shown that these amphibians are at risk [56]. Since 2018, an outbreak of the deadly fungus B. salamandrivorans has been detected in Barcelona.…”

Major Emerging Fungal Diseases of Reptiles and Amphibians

“…Cuban treefrogs can be infected with Bsal and, surprisingly, chytridiomycosis can develop in animals at the two highest zoospore dose exposures [ 126 ]. Moreover, different strains of Bsal might account for variations in susceptible species and epidemic profile, as was hypothesized following the isolation of Bsal in wild small-webbed fire-bellied toads ( Bombina microdeladigitora ) from Vietnam [ 121 , 127 ]. Current bans on amphibian transport that largely focus on halting the trade of urodele species may, therefore, be insufficient to prevent translocation of Bsal , especially as anurans constitute 99% of global amphibian trade [ 128 ].…”

“…In urodeles, only the terrestrial life stages are thought to be susceptible. Direct contact for at least eight hours is sufficient for transmission [ 118 ], although the delay between exposure and mortality in susceptible species is highly variable, ranging from 12–18 days in fire salamanders to seven weeks in gold-striped salamanders ( Chioglossa lusitanica ) [ 63 , 118 , 127 ]. In contrast to Bd , dermatological lesions present as multifocal ulcerative superficial epidermal lesions that are distributed over the entire body [ 63 , 64 ].…”

Divergent population responses following salamander mass mortalities and declines driven by the emerging pathogen Batrachochytrium salamandrivorans

“…Like its sister species Bd, the pathogen was probably introduced through the international amphibian trade from its centre of origin in East Asia [13]. Being particularly lethal to salamander species, however, Bsal was projected to have devastating effects on salamander biodiversity hotspots, most notably in North and Central America as well as southern Europe [14][15][16]. Its emergence was therefore signalled as a key conservation threat that has the potential to strongly amplify the amphibian extinction crisis [17].…”