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Chytridiomycosis in native Arizona frogs
Gregory A Bradley1, Philip C Rosen, Michael J Sredl
1Arizona Veterinary Diagnostic Laboratory, Department of Veterinary Science and Microbiology, University of Arizona, 2831 N. Freeway, Tucson, Arizona 85705, USA. gabrad@ag.arizona.edu
Journal of Wildlife Diseases
|February 13, 2002
Summary
Chytrid fungus (Batrachochytrium dendrobatidis) infection caused mortality in lowland leopard frogs (Rana yavapaiensis) and canyon tree frogs (Hyla arenicolor). Lesions and positive cultures confirmed the fungal pathogen in affected amphibian populations.
Area of Science:
- Amphibian Pathology
- Mycology
- Wildlife Disease Ecology
Background:
- Amphibian populations worldwide are declining, with infectious diseases implicated as a major driver.
- The chytrid fungus, Batrachochytrium dendrobatidis (Bd), has been identified as a significant pathogen responsible for amphibian mortality events.
- Previous studies have documented Bd infections in various amphibian species, but understanding its impact on specific populations requires ongoing investigation.
Purpose of the Study:
- To investigate the cause of mortality events in lowland leopard frogs (Rana yavapaiensis) and associated amphibian species.
- To identify the presence and characteristics of chytrid fungus infection (Batrachochytrium dendrobatidis) in affected populations.
- To differentiate Bd from other potential causes of mortality, such as bacterial or viral agents.
Main Methods:
- Necropsy and histopathological examination of affected adult and larval frogs from eight field sites.
- Gross and microscopic evaluation of skin lesions for characteristic signs of chytrid infection.
- Bacterial culturing and virus isolation from frog tissues to rule out other pathogens.
- Fungal culturing from skin samples of affected frogs to isolate and identify Batrachochytrium dendrobatidis.
Main Results:
- Characteristic lesions of chytrid fungus infection were observed in lowland leopard frogs (Rana yavapaiensis) and canyon tree frogs (Hyla arenicolor).
- Mortality events occurred during specific winter months across multiple years (1992-1999).
- Batrachochytrium dendrobatidis was successfully isolated from the skin of affected R. yavapaiensis and H. arenicolor, confirming the diagnosis. Bacterial and viral cultures were negative.
Conclusions:
- Batrachochytrium dendrobatidis is identified as the causative agent of mortality in the studied populations of lowland leopard frogs and canyon tree frogs.
- The findings highlight the significant impact of chytridiomycosis on vulnerable amphibian populations in the region.
- Continued monitoring and research are crucial for understanding and mitigating the effects of this devastating fungal pathogen on amphibian biodiversity.