Cranial ulceration in Atlantic salmon Salmo salar associated with Tetrahymena sp.

Abstract

Cranial ulceration in yearllng Atlantic salmon Salmo salar L. was associated with the presence of large numbers of a holotnchous cdiate tentahvely idenhfied as Tetrahymena sp.A pronounced subacute inflammation was seen in association with the invasion of head tlssues.Important pathological finhngs included erosion of the cramum accomparued by osteoclasts, perineuritis of cranial nerves, and w t u a l replacement of the epithelial Lining of the supraoptic canal by parasites.Whether or not the ciliates were the cause of the ulceration, treatment with f o r m a h reduced mortality m remaining fish.