Histology of snake fungal disease

(A) Underneath the β-layer of the epidermis is an accumulation of hypereosinophilic necrotic debris. The remaining epidermis is extensively ulcerated. Heterophils and macrophages infiltrate the underlying dermis. Skin, PAS. (B) Necrotic debris is found above the β-layer of the outer generation (BO) and between the BO and the β-layer of inner generation (BI). Fungal hyphae are widespread within the necrotic debris but are also found infiltrating the BI and within the mesos layer (ML, arrow head). Skin AS. (C) Arthroconidia (asterisk) are found superficially and myriad fungal hyphae (arrows) infiltrate the necrotic debris. Skin, PAS (D) Rectangular 2 x 5 µm arthroconidia (asterisk) are often found on the air-lesion interface (asterisk). Skin, PAS. (D). PAS-positive fungal hyphae (arrow) are parallel walled, of up to 5 µm in width and exhibit occasional septations and non-dichotomous branching. Skin, PAS. (β-Layer of outer generation (BO), β-Layer of inner generation (BI), ML Mesos layer (ML), α-layer (AL), Stratum germinativum (SG)