Continent-wide recent emergence of a global pathogen in African amphibians

Abstract

IntroductionEmerging infectious diseases are increasingly recognized as a global threat to wildlife. Pandemics in amphibians, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), have resulted in biodiversity loss at a global scale. Genomic data suggest a complex evolutionary history of Bd lineages that vary in pathogenicity. Africa harbors a significant proportion of global amphibian biodiversity, and multiple Bd lineages are known to occur there; yet, despite the decline of many host species, there are currently no described Bd-epizootics. Here, we describe the historical and recent biogeographical spread of Bd and assess its risk to amphibians across the continent of Africa.MethodsWe provide a 165-year view of host-pathogen interactions by (i) employing a Bd assay to test 4,623 specimens (collected 1908–2013); (ii) compiling 12,297 published Bd records (collected 1852–2017); (iii) comparing the frequency of Bd-infected amphibians through time by both country and region; (iv) genotyping Bd lineages; (v) histologically identifying evidence of chytridiomycosis, and (vi) using a habitat suitability model to assess future Bd risk.ResultsWe found a pattern of Bd emergence beginning largely at the turn of the century. From 1852–1999, we found low Bd prevalence (3.2% overall) and limited geographic spread, but after 2000 we documented a sharp increase in prevalence (18.7% overall), wider geographic spread, and multiple Bd lineages that may be responsible for emergence in different regions. We found that Bd risk to amphibians was highest in much of eastern, central, and western Africa.DiscussionOur study documents a largely overlooked yet significant increase in a fungal pathogen that could pose a threat to amphibians across an entire continent. We emphasize the need to bridge historical and contemporary datasets to better describe and predict host-pathogen dynamics over larger temporal scales.

Archival mitogenomes identify invasion by the Batrachochytrium dendrobatidis CAPE lineage caused an African amphibian extinction in the wild

“…Spatial surveillance and predictive ecological niche modelling of Bd in South Africa demonstrates that Bd GPL and Bd CAPE occupy different ecotypes, with the latter occurring across cooler higher altitude environments [ 45 ]. Our evidence of Bd CAPE causing lethal chytridiomycosis in the Udzungwa Kihansi spray toads expands the range of this lineage into a new area and highlights the threat posed to amphibian hosts by other, non- Bd GPL lineages [ 42 , 46 ].…”

Preparing for a Bsal invasion into North America has improved multi-sector readiness

“…Several key products have been completed: 1) establishment and a description of the structural underpinnings of the Bsal and Bd Amphibian Disease web portal (amphibiandisease.org), with an important roadmap for the incorporation of the legacy Bd-maps.net dataset (Koo et al, 2021); 2) imports of USGS survey results for Bsal in 2014-2017 (USA: Waddle et al, 2020), results from the Bsal Consortium of Germany (see special edition of Salamandra, Volume 56[3]), and integration of the SNAPS effort as an ongoing project in the web portal (Figure 4); and 3) a global Bd update (Olson et al, 2021b) with transference of the Bd-maps.net database (formerly archived at Imperial College, London, UK: Olson et al, 2013) updated through 2019 to the new web portal, inclusive of database DOI references. Although the Bsal data repository is growing, the utility of our web portal to the world community is supported by recent Bd metadata analyses and risk-assessment publications using exported globally compiled data archived in the Amphibian Disease database that focus conservation-planning attention on more defined geographies and taxa (e.g., Suriname: Rawien and Jairam-Doerga, 2022; West Africa: Ghose et al, 2023).…”

Ecological Civilization COP 15 and Amphibian Sustainability through Reproduction Technologies, Biobanking, and Conservation Breeding Programs (RBCs)

“…Most generic threats to be funded by the 2007 ACAP are now highly prioritised in global policy, or well researched by academic programs, with the issues of over-harvest and pathogens [242][243][244][245][246] as ubiquitous threats largely to be addressed through national and international trade regulation (sections 2.2,2.4). However, in 2023 participants of the ninth World Congress of Herpetology and survey respondents produced a similar list of popular academic research priorities to the 2007 ACAP, including the climate crisis, pathogens, biodiversity, populations, and habitat, within a framework of polarised boundaries between anthropogenic activities and nature (section 1).…”