ELUCIDATING THE PATHOGENESIS OF BATRACHOCHYTRIUM SALAMANDRIVORANS CHYTRIDIOMYCOSIS

Amphibian species worldwide are facing severe threats to their biodiversity including infectious disease, climate change, and habitat destruction. With these increasing threats, there is a growing need to explore disease pathogenesis and understand amphibian health. One of the most important emerging infectious diseases of amphibians is caused by the fungal pathogen Batrachochytrium salamandrivorans (Bsal). Bsal was recently discovered and is of global concern due to its potential to cause high mortality in amphibians, primarily salamander species. We investigated disease pathogenesis using two newt species with known susceptibility to Bsal chytridiomycosis (Notophthalmus viridescens and Taricha granulosa) as models. Taricha granulosa were exposed to Bsal and allowed to reach various stages of disease progression. Blood was collected immediately postmortem for hematological and biochemical analysis as well as plasma protein electrophoresis. Histologic skin lesions associated with Bsal infection were quantified and graded for each animal. Electrolyte imbalances and dehydration due to epidermal damage were shown to likely be the primary cause of morbidity and mortality in diseased T. granulosa. In a separate study, N. viridescens were exposed to one of four Bsal zoospore doses at one of three environmental temperatures. Individuals exposed at 14°C had increased lesion counts compared to those exposed at 6°C. Individuals exposed at 22°C did not become infected. Also, increased lesion counts were associated with decreased survival rate, and the most common anatomic sites for lesions of any grade were the hindlimbs, cloacal region, and tail. Independent of Bsal investigations, protein electrophoresis was performed on plasma collected from one anuran and six urodelan species that were clinically normal. This study provided novel representative electrophoretograms for each species and lay groundwork for future studies to establish reference intervals in these as well as other amphibian species. Overall, the findings of my research provide insight into the pathogenesis of Bsal chytridiomycosis and provide evidence that plasma protein electrophoresis may be a useful diagnostic tool in amphibians. This information can be used to identify possible disease mitigation options for Bsal chytridiomycosis in captive settings, provide guidance for Bsal surveillance programs, and will be helpful in future amphibian health investigations.