Chytridiomycosis in Asian Amphibians, a Global Resource for Batrachochytrium dendrobatidis (Bd) Research

Abstract

Chytridiomycosis is an emerging infectious disease affecting amphibians globally and it is caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd ) . Chytridiomycosis has caused dramatic declines and even extinctions in wild amphibian populations in Europe, Australia, Central and North America. Spanning over two and a half decades, extensive research has led to discovery of epizootic and enzootic lineages of this pathogen. However, the Bd –amphibian system had garnered less attention in Asia until recently when an ancestral Bd lineage was identified in the Korean peninsula. Amphibians co-exist with the pathogen in Asia, only sub-lethal effects have been documented on hosts. Such regions are ‘coldspots’ of infection and are an important resource to understand the dynamics between the enzootic pathogen— Bd and its obligate host—amphibians. Insights into the biology of infection have provided new knowledge on the multi-faceted interaction of Bd in a hyperdiverse Asian amphibian community. We present the findings and highlight the knowledge gap that exists, and propose the ways to bridge them. We emphasize that chytridiomycosis in Asia is an important wildlife disease and it needs focussed research, as it is a dynamic front of pathogen diversity and virulence.

Occurrence of Pathogenic Chytrid Fungi Batrachochytrium Salamandrivorans and Batrachochytrium Dendrobatidis in the Hong Kong Newt (Paramesotriton Hongkongensis) and Other Wild and Imported Amphibians in a Subtropical Asian Region

“…Our finding of Bd in local amphibians only in a single P. hongkongensis agrees with the general observation that no lethal outbreak of Bd infection has been recorded from Asia to date; Asia is referred to as a “cold spot” of Bd infection because Bd prevalence is generally low and where it is found, pathogen loads on infected amphibians are very low (Sreedharan and Vasudevan 2021). Our result is similar to that from a previous local study in 2007, which found wild individuals of four native amphibian species ( A. hongkongensis , Paa exilispinosa , P. spinosa , and Rana chloronota ) all negative for Bd (Rowley et al 2007).…”

“…Many wild Asian newts, including some of the suggested Asian reservoir hosts, are overhunted and commonly traded to meet the growing demands from domestic and international pet markets (Rowley et al 2016; Kitade and Wakao 2022). Therefore, understanding the prevalences of Bsal and Bd in wild amphibians and the geographical distribution of infected populations, especially those in Asia, and assessing the risk of pathogen introduction from animal trade are critical for conserving global amphibian biodiversity (Sreedharan and Vasudevan 2021).…”

Chytridiomycosis in Sri Lanka: Predicting the future of a global amphibian hotspot

“…The present scientific consensus is that Bd is Korean in origin, and mainland Asian frog populations have a low prevalence and load of Bd (O'Hanlon et al, 2018; Sreedharan & Vasudevan, 2021). However, Sri Lanka is an island where the biota speciated in isolation for at least the last 10,000 years, with 86% endemism in frogs (Pethiyagoda & Sudasinghe, 2021).…”

“…In light of the recent detections of Bd in the Asian region (Fu & Waldman, 2019; Rahman et al, 2020; Sreedharan & Vasudevan, 2021), and the already established spread of Bd in other parts of the world (Mendelson et al, 2006; Azat et al, 2022), the methods discussed here would enable scientists and policymakers to identify species and regions in need of immediate conservation action. In areas such as the Western Ghats and Taiwan, the existing high diversity of amphibians (Sankararaman et al, 2021; Schmeller et al, 2022) is already facing a myriad of challenges (Sankararaman et al, 2021), including Bd (Dahanukar et al, 2013; Thorpe et al, 2018; Schmeller et al, 2022).…”

A Universal and Efficient Detection of Chytridiomycosis Infections in Amphibians Using Novel Quantitative PCR Markers

“…Initially, geographic regions with high levels of Bd infection and frog mortality were the major focus of research, and then areas with enzootic Bd have been recognized. Particularly, from Asia, such areas are yet to be identifed [4]. Korea, China, Japan, and India are among the countries where Bd is enzootic [5][6][7][8][9][10].…”