HISTOPATHOLOGY OF SNAKEHEAD, CHANNA-STRIATUS (BLOCH), EXPERIMENTALLY INFECTED WITH THE SPECIFIC APHANOMYCES FUNGUS ASSOCIATED WITH EPIZOOTIC ULCERATIVE SYNDROME (EUS) AT DIFFERENT TEMPERATURES

Snakesheads, Channa striatus (Bloch), were inoculated with a spore sus pension of the specific pathogenic Aphanomyces, isolated from fish aff ected by epizootic ulcerative syndrome (EUS), in South East Asia. Fish were held at three different temperatures: 19, 26 and 31-degrees-C. H istological changes induced by the infection are described. In the ear ly stages of the disease, degenerative changes were observed in all sa mples, but inflammatory infiltrate was much more marked in fish kept a t 26 and 31-degrees-C. By 8 days post-injection, extensive mycotic gra nulomatosis was observed in the samples kept at 26 and 31-degrees-C. T he fish kept at 19-degrees-C developed a severe invasive myonecrosis w ith limited macrophage response. From 14 to 28 days post-injection, he aling became well established at 26 and 31-degrees-C and surviving fis h kept at these temperatures recovered completely by 28 days. The lesi on was still progressing at 21 days post-injection in fish kept at 19- degrees-C, and all such fish succumbed by this time. Thus, mortalities in the fish kept at 19-degrees-C were considerably higher than in the groups of fish kept at 26 and 31-degrees-C. The findings help to expl ain why mortalities from EUS occur when water temperatures are low.