Nodular gill disease (amoebic gill infestation) in arctic char, Salvelinusalpinus

Two groups of Arctic char (Salvelinus alpinus) and one of rainbow trout (On corhynchus mykiss) from a commercial fish farm in eastern Canada were found to have mixed infection of the gills with Flavobacterium branchiophilum (t he causative agent of bacterial gill disease (BGD)) and amoebae similar to those responsible for nodular gill disease (NGD). The diagnoses were con fi rmed by immunofluorescence antibody testing and transmission electron micro scopy. The gill lesions were typical for a mixed BGD and NGD infection and the extensive and dramatic hyperplasia of filament epithelium was character istic of NGD. The diagnosis of NGD in Arctic char in eastern Canada represe nts both a geographical and species extension for this infection. To date, within commercially farmed salmonid populations, NGD has been reported only in central Canada in rainbow trout. (C) 1999 Harcourt Publishers Ltd.