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Disease


Cave Bd sampling
Left to Right: Tabby Cavendish (Great Smoky Mountains NP), Brian Gregory (USGS), and Jamie Barichivich (ARMI) swabbing salamanders for Batrachochytrium dendrobatidis (Bd) in Rockhouse Cave, Wheeler NWR, Alabama. Photo by: Alan Cressler.

ARMI conducts original research on various amphibian diseases in the lab and field. Our research has included estimating the impacts of diseases on the growth of populations, developing and testing potential treatments, affects of stressors on susceptibility to disease, how diseases are transmitted in the wild, and how to model disease distributions and spread.

ARMI disease research is conducted throughout the country, but ARMI pathologist Dr. David Green is based at the National Wildlife Health Center in Madison, Wisconsin, and coordinates the health screenings and investigations of amphibian mortalities (e.g., identification, pathology) in addition to collaborating on many disease research projects.

Amphibians at our long-term monitoring sites are periodically screened for diseases and we investigate mass mortality events.

Resources

National Wildlife Health Center - ARMI

ARMI Products on Disease

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This is an ARMI Product. A pesticide paradox: Fungicides indirectly increase fungal infections
Authors: Rohr JR, Brown J, Battaglin WA, McMahon TA, Relyea RA | Date: 2017-07-28 | Outlet: Ecological Applications, in press DOI: 10.1002/eap.1607
Abstract. There are many examples where the use of chemicals have had profound unanticipated consequences, such as fertilizers reducing crop yields (paradox of enrichment) and insecticides increasing insect pests (by reducing natural biocontrol). Recently, the application of agrochemicals, such as agricultural disinfectants and fungicides, has been explored as an approach to curb the pathogenic fungus, Batrachochytrium dendrobatidis (Bd), which is associated with worldwide amphibian declines. However, the long-term, net effects of early-life exposure to these chemicals on amphibian disease risk have not been thoroughly investigated. Using a combination of laboratory experiments and analysis of data from the literature, we explored the effects of fungicide exposure on Bd infections in two frog species. Extremely low concentrations of the fungicides azoxystrobin, chlorothalonil, and mancozeb were directly toxic to Bd in culture. However, estimated environmental concentrations of the fungicides did not reduce Bd on Cuban tree frog (Osteopilus septentrionalis) tadpoles exposed simultaneously to any of these fungicides and Bd, and fungicide exposure actually increased Bd-induced mortality. Additionally, exposure to any of these fungicides as tadpoles resulted in higher Bd abundance and greater Bd-induced mortality when challenged with Bd post-metamorphosis, an average of 71 days after their last fungicide exposure. Analysis of data from the literature revealed that previous exposure to the fungicide itraconazole, which is commonly used to clear Bd infections, made the critically endangered booroolong frog (Litoria booroolongensis) more susceptible to Bd. Finally, a field survey revealed that Bd prevalence was positively associated with concentrations of fungicides in ponds. Although fungicides show promise for controlling Bd, these results suggest that, if fungicides do not completely eradicate Bd or if Bd re-colonizes, exposure to fungicides has the potential to do more harm than good. To ensure that fungicide applications have the intended consequence of curbing amphibian declines, researchers must identify which fungicides do not compromise the pathogen resistance mechanisms of amphibians.

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This is an ARMI Product. Identifying Species Conservation Strategies to Reduce Disease-Associated Declines
Authors: Gerber B, Converse S, Muths E, Crokett H, Mosher B, Larissa B
Emerging infectious diseases (EIDs) are a salient threat to many animal taxa, causing local and global extinctions, altering communities and ecosystem function. The EID chytridiomycosis is a prominent driver of amphibian declines, which is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). To guide conservation policy, we developed a predictive decision-analytic model that combines empirical knowledge of host-pathogen metapopulation dynamics with expert judgment regarding effects of management actions, to select from potential conservation strategies. We apply our approach to a boreal toad (Anaxyrus boreas boreas) and Bd system, identifying optimal strategies that balance tradeoffs in maximizing toad population persistence and landscape-level distribution, while considering costs. The most robust strategy is expected to reduce the decline of toad breeding sites from 53% to 21% over 50 years. Our findings are incorporated into management policy to guide conservation planning. Our online modeling application provides a template for managers of other systems challenged by EIDs.

This is an ARMI Product. Pathogenic lineage of Perkinsea causes mass mortality of frogs across the United States
Authors: Isidoro-Ayza M, Lorch JM, Grear DA, Winzeler M, Calhoun DL, Barichivich W | Date: 2017-08-31 | Outlet: Scientific Reports 7, Article number: 10288 | Format: .PDF
Emerging infectious diseases such as chytridiomycosis and ranavirus infections are considered important contributors to the worldwide decline of amphibian populations. We reviewed data on 247 anuran mortality events in 43 states of the United States from 1999 ? 2015. Our findings suggest that a severe infectious disease of tadpoles caused by a protist belonging to the phylum Perkinsea might represent the third most common infectious disease of anurans after ranavirus infections and chytridiomycosis. Severe Perkinsea infections (SPI) were systemic and led to multiorganic failure and death. The SPI mortality events affected numerous anuran species and occurred over a broad geographic area, from boreal to subtropical habitats. Livers from all PCR-tested SPI-tadpoles were positive for the Novel Alveolate Group 01 (NAG01) of Perkinsea, while only 2.5% of apparently normal tadpole livers tested positive, suggesting that subclinical infections are uncommon. Phylogenetic analysis demonstrated that SPI is associated with a genetically distinct clade of NAG01 Perkinsea. These data suggest that this virulent Perkinsea clade is an important pathogen of frogs in the United States. Given its association with mortality events and tendency to be overlooked, the potential role of this emerging pathogen in amphibian declines on a broad geographic scale warrants further investigation


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