Studies on ulcerative dermal necrosis of salmonids

Abstract

The gross pathology and histopathology of a series of 150 cases of UDN disease of salmon Safmo sulur L. from a number of Scottish rivers is described. The lesions appeared first as small grey areas on the heads of affected fish, which gradually enlarged in size, ulcerated and became infected with fungus of the Saprolegniu group. Histologically, the earliest lesion was an acantholysis of the suprabasal cells of the epidermis developing into transient bullae which rapidly sloughed to produce a raggcd irregular epiderm's. Once the base‐ment membrane was breached secondary infection by fungi rapidly ensued. The histopathology, in the early stages, was consistent with possible viral infection, or anoxic atrophy but it was considered that the most similar lesion from mammalian experi‐ence, was that of the Pemphigus group of dermatoses.