Widespread occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in the southeastern USA

Abstract

From 1999 to 2006, we sampled >1200 amphibians for the fungal pathogen Batrachochytrium dendrobatidis (Bd) at 30 sites in the southeastern USA. Using histological techniques or PCR assays, we detected chytrid infection in 10 species of aquatic-breeding amphibians in 6 states. The prevalence of chytrid infection was 17.8% for samples of postmetamorphic amphibians examined using skin swab-PCR assays (n = 202 samples from 12 species at 4 sites). In this subset of samples, anurans had a much higher prevalence of infection than caudates (39.2% vs. 5.5%, respectively). Mean prevalence in ranid frogs was 40.7%. The only infected salamanders were Notophthalmus viridescens at 3 sites. We found infected amphibians from late winter through late spring and in 1 autumn sample. Although we encountered moribund or dead amphibians at 9 sites, most mortality events were not attributed to Bd. Chytridiomycosis was established as the probable cause of illness or death in fewer than 10 individuals. Our observations suggest a pattern of widespread and subclinical infections. However, because most of the sites in our study were visited only once, we cannot dismiss the possibility that chytridiomycosis is adversely affecting some populations. Furthermore, although there is no evidence of chytrid-associated declines in our region, the presence of this pathogen is cause for concern given global climate change and other stressors. Although presenceabsence surveys may still be needed for some taxa, such as bufonids, we recommend that future researchers focus on potential population-level effects at sites where Bd is now known to occur.

Fitness Consequences of Infection by Batrachochytrium dendrobatidis in Northern Leopard Frogs (Lithobates pipiens)

“…Bd has been detected, often with high prevalence, in amphibians of eastern North America (Longcore et al 2007;Rothermel et al 2008;Gaertner et al 2009;Kinney et al 2011;Chatfield et al 2012). However, despite the fungus being common, no mass die-offs have been attributed to chytridiomycosis in the region.…”

“…In some parts of the world this pathogen has caused mass die-offs and even extinctions (Lips et al 2005;Skerratt et al 2007), whereas in others amphibians are heavily infected but show no acute signs of disease (Rothermel et al 2008;Kinney et al 2011). Amphibians in eastern North America fall into the latter category, where infection prevalence may be high (Longcore et al 2007;Rothermel et al 2008;Gaertner et al 2009;Kinney et al 2011;Chatfield et al 2012) yet mass die-offs attributable to chytridiomycosis have not been observed. Acute infections and death have obvious fitness consequences for amphibians; however, sublethal and chronic infections may have important fitness consequences as well.…”

Neurotropic mesomycetozoean-like infection in larvae of the southern toad Anaxyrus terrestris in Florida, USA

“…In Florida, as elsewhere, amphibian pathogens, such as frog virus 3 (FV3, the type species for the genus Ranavirus), protozoan alveolate parasites (Cook 2008, Rothermel et al 2008, Landsberg et al 2013) and chytrid fungi (e.g. Batrachochytrium dendrobatidis [Bd]; Rothermel et al 2008, Rizkalla 2009, 2010 are considered important mortality factors (Rothermel et al 2008, Landsberg et al 2013.…”

Experimental infection of North American plethodontid salamanders with the fungus Batrachochytrium dendrobatidis

“…Endemic species on islands are vulnerable to population declines that result from disease introduction (Warner 1968). The presence in the southeastern USA of Batrachochytrium dendrobatidis, a fungal pathogen of amphibians, is a potential threat to the region's diverse salamander assemblages (Rothermel et al 2008). B. dendrobatidis has been detected in wild populations of amphibians in at least 2 sites in the southern Appalachian Mountains, one in northeastern Georgia and one in western North Carolina (Rothermel et al 2008).…”

“…The presence in the southeastern USA of Batrachochytrium dendrobatidis, a fungal pathogen of amphibians, is a potential threat to the region's diverse salamander assemblages (Rothermel et al 2008). B. dendrobatidis has been detected in wild populations of amphibians in at least 2 sites in the southern Appalachian Mountains, one in northeastern Georgia and one in western North Carolina (Rothermel et al 2008). Investigations of disease susceptibility and population trends of plethodontid salamanders in the Appalachian Highlands are urgently needed, given recent reports of their declines in this region (Highton 2005) and in the Mesoamerican Highlands (Lips & Donnelly 2005).…”