ABSTRACT: Fungi morphologically consistent with class Oomycetes were recovered on primary culture from 20 of 22 ulcers on 21 fish with epizootic ulcerative syndrome (EUS) collected from 5 sites in the Philippines. Eleven primary isolates, and the unifungal cultures derived from them, were identified as Aphanomyces spp.; the remaining 9 primary isolates were lost through contaminant overgrowth. The Aphanomyces isolates were morphologically and culturally indistinguishable from those reported from red spot disease (RSD) in Australia. Comparison of 4 representative Aphanomyces isolates from Australian fish with RSD and 3 representative Aphanomyces isolates from Philippine fish with EUS, using SDS-PAGE (sodium dodecyl sulphate polyacrylamide gel electrophoresis), revealed similar peptide banding profiles, indicative of a single Aphanomyces species. These findings, combined with epizootiological and pathological similarities between EUS and RSD, suggest the 2 syndromes are identical, and that a single Aphanomyces sp. may be the primary infectious cause.

KEY WORDS: Aphanomyces . Ulcer . EUS . Philippines . Australia

Published in DAO Vol. 21, No. 3 (1995) on March 30
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1995