Figure 2.

Pathogen load and host skin changes during experimental Bd infection of Eastern hellbender salamanders. (a,b) Bd load in experimentally infected hellbender salamanders at each longitudinal sampling event during experimental infection. Bd load is represented as mean and s.e. of Log₁₀ Bd ITS1 copies in (a) all infected animals (merged low- and high-dose infection groups), summarized by vaccination group and (b) all vaccinated animals (merged sham, topical and oral vaccination groups), summarized by Bd infection dose. Animals were infected on experimental day 89. All Bd (+) hellbenders developed high pathogen burdens of greater than or equal to 1E5 Log₁₀ Bd ITS1 copies within 28 days of infection and maintained high-Bd loads for the duration of the challenge. All control animals remained Bd (−) for the duration of the experiment. An incidental cold-shock occurred on experimental day 90, indicated by the black triangle. There was no overall effect of (a) vaccination or (b) Bd dose on infection intensity as measured by AUDPC. (c) Clinical chytridiomycosis in experimentally Bd-infected eastern hellbender salamanders. Skin coloration was altered by Bd infection; Bd (−) animals maintained normal brown skin coloration with clearly defined markings, Bd (+) animals developed diffuse opaque blue-grey skin coloration and exhibited increased skin sloughing. Hellbender epidermal structure was altered by Bd infection; the Bd (+) hellbender skin exhibits overall thickening of the epidermis (brackets), thickening of the exterior keratinized epidermis (black arrow) with abundant intracellular Bd (black circle), epidermal oedema (red arrow), and an increase in distance from dermal (red arrowhead) and epidermal (black arrowhead) capillaries to the surface of the skin. All histopathology images are magnified 200×.