Tracking, Synthesizing, and Sharing Global Batrachochytrium Data at AmphibianDisease.org

Emerging infectious diseases have been especially devastating to amphibians, the most endangered class of vertebrates. For amphibians, the greatest disease threat is chytridiomycosis, caused by one of two chytridiomycete fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). Research over the last two decades has shown that susceptibility to this disease varies greatly with respect to a suite of host and pathogen factors such as phylogeny, geography (including abiotic factors), host community composition, and historical exposure to pathogens; yet, despite a growing body of research, a comprehensive understanding of global chytridiomycosis incidence remains elusive. In a large collaborative effort, Bd-Maps was launched in 2007 to increase multidisciplinary investigations and understanding using compiled global Bd occurrence data (Bsal was not discovered until 2013). As its database functions aged and became unsustainable, we sought to address critical needs utilizing new technologies to meet the challenges of aggregating data to facilitate research on both Bd and Bsal. Here, we introduce an advanced central online repository to archive, aggregate, and share Bd and Bsal data collected from around the world. The Amphibian Disease Portal (https://amphibiandisease.org) addresses several critical community needs while also helping to build basic biological knowledge of chytridiomycosis. This portal could be useful for other amphibian diseases and could also be replicated for uses with other wildlife diseases. We show how the Amphibian Disease Portal provides: (1) a new repository for the legacy Bd-Maps data; (2) a repository for sample-level data to archive datasets and host published data with permanent DOIs; (3) a flexible framework to adapt to advances in field, laboratory, and informatics technologies; and (4) a global aggregation of Bd and Bsal infection data to enable and accelerate research and conservation. The new framework for this project is built using biodiversity informatics best practices and metadata standards to ensure scientific reproducibility and linkages across other biological and biodiversity repositories.

Global Patterns of the Fungal Pathogen Batrachochytrium dendrobatidis Support Conservation Urgency

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) is a skin pathogen that can cause the emerging infectious disease chytridiomycosis in susceptible species. It has been considered one of the most severe threats to amphibian biodiversity. We aimed to provide an updated compilation of global Bd occurrences by host taxon and geography, and with the larger global Bd dataset we reanalyzed Bd associations with environmental metrics at the world and regional scales. We also compared our Bd data compilation with a recent independent assessment to provide a more comprehensive count of species and countries with Bd occurrences. Bd has been detected in 1,375 of 2,525 (55%) species sampled, more than doubling known species infections since 2013. Bd occurrence is known from 93 of 134 (69%) countries at this writing; this compares to known occurrences in 56 of 82 (68%) countries in 2013. Climate-niche space is highly associated with Bd detection, with different climate metrics emerging as key predictors of Bd occurrence at regional scales; this warrants further assessment relative to climate-change projections. The accretion of Bd occurrence reports points to the common aims of worldwide investigators to understand the conservation concerns for amphibian biodiversity in the face of potential disease threat. Renewed calls for better mitigation of amphibian disease threats resonate across continents with amphibians, especially outside Asia. As Bd appears to be able to infect about half of amphibian taxa and sites, there is considerable room for biosecurity actions to forestall its spread using both bottom-up community-run efforts and top-down national-to-international policies. Conservation safeguards for sensitive species and biodiversity refugia are continuing priorities.

THE CHYTRID BLINDERS 2.0: HOW ARE WE DOING?

Amphibians are declining around the world and infectious diseases are thought to play a key role in these declines, along with habitat destruction and other environmental factors. Since the late 1900s, several emerging infections have been identified in amphibians. The chytrids, of which there are two known to affect amphibians, Batrachochytrium dendtrobatids, and B. salamandrivorans; and ranaviruses are perhaps the most well-known and studied. There are also other, lesser known and studied pathogenic agents such as Perkinsea spp. and herpesviruses; that have emerged in approximately the same timeline, which may also be contributing to amphibian population dynamics. In this piece we examine the progress that has been made over the past decade in understanding ‘The Big Three’ and specifically how the emergence of B. salamandrivorans has brought together much of the amphibian disease world in the last half of the 2010s.

Physiology provides a window into how the multi-stressor environment contributes to amphibian declines

The amphibian disease chytridiomycosis, caused by two fungal pathogens in the genus Batrachochytrium, has caused the greatest vertebrate biodiversity loss due to disease in recorded history. Both the pathogens and their amphibian hosts are impacted by biotic and abiotic conditions that are rapidly changing due to anthropogenic causes, challenging our understanding of how the host–pathogen relationship will shift in the future. By examining this problem through a physiological lens, we can elucidate the mechanisms driving increased susceptibility to disease. This chapter first examines the physiological tools that can be used by amphibian biologists to measure aspects of immune function, stress physiology, and energy expenditure, and the main environmental drivers of these physiological shifts. Then, we explore case studies that have linked environmental change, immune function, and shifts in disease susceptibility to inform amphibian conservation and management.