A rural property was observed for one year to obtain seasonal observations of Edwardsiella septicemia in tilapias (Oreochromis sp.) from an integrated fish farm (using pig excrements as food). Fifty tilapias on summer, forty-five on autumn, fifty-five on winter and one hundred and five on spring were collected and evaluated microbiologically for the presence of Edwardsiella tarda. Samples of the external surface (skin, gills and fin), intestines and muscle were analyzed. Fishes were transported alive to the laboratory, and maintained for five days for observation. The external signs observed were opacity of cornea, respiratory difficulty, disordered swimming, nodules on gills, hemorrhagic lesions under the skin and fins and incoordination of the posterior part of the body. In general, after three days of observation, the tilapias died. At necropsy, ascites with the distension of the celomatic cavity, hemorrhagic and necrotic lesions in the liver, spleen and kidneys were found. Hemorrhagic enteritis was observed in the gut tube. Edwardsiella tarda isolated presented the following biochemical profile: negative urea, sucrose, phenylalanine desaminase and malonate utilization, and positive indole, methyl red, H2S, motility, glucose with gas production and lysine decarboxylase. The mortality rates were 69.9% on spring, 63.6% on winter, 48.0% on summer and 40.0% on autumn, highest rates occurring on spring and winter (P<0,05).
Fish; tilapia; Edwardsiella septicemia; Edwardsiella tarda; fish-pig integration
