PATHOGENICITY AND CULTURE STUDIES COMPARING THE APHANOMYCES INVOLVED IN EPIZOOTIC ULCERATIVE SYNDROME (EUS) WITH OTHER SIMILAR FUNGI

Pathogenicity and cultural experiments described here provide futher e vidence that a distinct species of Aphanomyces is responsible for much of the characteristic pathology of epizootic ulceration syndrome (EUS ). Zoospores from 58 fungal isolates were injected intramuscularly in snakehead fish, Channa striata (Bloch). These fungi comprised: Aphanom yces strains isolated from EUS-affected fish; saprophytic Aphanomyces, Achlya and Saprolegnia spp. from infected waters; and further saprole gniaceous fungi involved in other diseases of aquatic animals. Only th e Aphanomyces strains isolated from fish affected by EUS, Australian r ed spot disease (already considered synonymous with EUS) or mycotic gr anulomatosis described from Japan were able to grow invasively through the fish muscle and produce the distinctive EUS lesions. In cont rast to Aphanomyces astaci Schikora, the EUS-Aphanomyces was shown to be u nable to infect noble crayfish, Astacus astacus L. The snakehead-patho genic strains were further distinguished from all the other fungi unde r comparison by their characteristic temperature-growth profile and in ability to grow on certain selective fungal media.