Associating anatomical and clinical pathology with Bsal chytridiomycosis in the rough skinned newt (Taricha granulosa)
Grzelak, A., R. Kumar, K. Ash, E. D. Carter, B. A. Bajo, M. Bohanon, A. C. Peterson, A. E. Towe, M. J. Gray, and D. L. Miller.  2019.  Wildlife Disease Association International Conference.

Abstract:
The anatomic pathology of Batrachochytrium salamandrivorans (Bsal) has been described in European newt species; however, the clinical pathology that occurs as the disease progresses remains an enigma. For a similar fungus, B. dendrobatidis (Bd), changes in blood electrolytes that lead to host paralysis and cardiac arrest have been reported. We hypothesized that newts experiencing Bsal chytridiomycosis would have similar changes in electrolytes, because like Bd, Bsal damages the epidermis hence likely affects skin osmoregulation – a key physiological process that influences blood chemistry. To test this hypothesis, we exposed a North American newt species (Taricha granulosa) to water baths containing one of four concentrations of Bsal zoospores (5x103, 5x104, 5x105, or 5x106) known to elicit disease (n = 5 newts per zoospore dose; n=2 controls) and monitored their condition for up to 52 days post-exposure. At euthanasia, blood was collected from the heart using heparinized capillary tubes, a blood smear was prepared, and a portion of whole blood was added to Natt Herrick’s solution for total blood cell counts. The remaining blood was centrifuged and plasma collected for blood chemistry profiles and protein electrophoresis. The newts were preserved in formalin and processed for histological examination. Target lesions began to appear primarily on the heads of the newts within the 105 and 106 groups, and as early as 3 days post-exposure in the 106 group. Digits on the newts were red to dark brown with occasional target lesions. Microscopically, target lesions presented as partial to full depth crater-like areas of epidermal necrosis with intralesional thalli. Initial biochemical results revealed decreases in sodium, chloride, and potassium in terminal stages of the disease (5x106 dose) similar to Bd. Identifying biochemical changes associated with Bsal chytridiomycosis will help elucidate pathogenesis and be key to developing management strategies and exploring treatment options in susceptible species.