EXPERIMENTAL INDUCTION OF LESIONS IN SNAKEHEADS (OPHICEPHALUS-STRIATUS) AND CATFISH (CLARIAS-BATRACHUS) WITH AEROMONAS-HYDROPHILA, AQUASPIRILLUM SP., PSEUDOMONAS SP. AND STREPTOCOCCUS SP

Isolates of Aquaspirillum sp., Pseudomonas sp., and Streptococcus sp. recovered from epizootic ulcerative syndrome (EUS)-affected snakeheads (Ophicephalus striatus) in Thailand as well as an isolate of Aeromona s hydrophila recovered from EUS-affected snakeheads in the Philippines were characterized and identified. Each isolate was injected intramus cularly (IM) into healthy catfish (Clarias batrachus) and snakeheads ( O. striatus). Results showed in tests with C. batrachus that 24 h afte r injection, Aquaspirillum sp., Pseudomonas sp., Streptococcus sp. and A. hydrophila induced slight, slight, moderate and severe dermomuscul ar necrotic lesions, respectively. Among O. striatus, only A. hydrophi la induced severe lesions. Streptococcus sp. induced slight lesions 2 days post-injection which healed rapidly, while Aquaspirillum sp. and Pseudomonas sp. did not manifest any dermal lesions. Experiments indic ated that among the four EUS-associated test bacteria, A. hydrophila w as the most pathogenic, inducing severe dermomuscular necrotic lesions in intramuscularly injected catfish (C. batrachus) and snakeheads (O. striatus). Differences in the susceptibility of O. striatus and C. ba trachus to Aquaspirillum sp., Pseudomonas sp. and Streptococcus sp. we re evident. Furthermore, this is the first evidence of the association between Aquaspirillum sp. and diseased fish.