Fatalities due to serious Yersinia bacterial infection in rainbow trout in Meshkin Shahr

Objective: Yersinia ruckeri is known to be the etiological agent responsible for the enteric red mouth (ERM) disease of fish. ERM disease is spread throughout the world and affects mainly intensive aquaculture of trout and salmon. Disease outbreaks have a relationship with stress conditions. In this case, serious fatalities were reported among 100 gram rainbow trouts in a cold water fish breeding center in Meshkin Shahr. Method & Materials: In suspected fish, darkness and bleeding in their mouths, skins and fins were observed. The fish were swimming at edges of the pool and ascit was clearly obvious in some of them. After transferring 15 of infected fish to the laboratory and accomplishing autopsy on some of alive fish, bleeding was seen in their inner organs of their body. Kidney, spleen and liver tissues were cultured in macconkey and blood agar. After 48-72 hours round- yellow colonies was seen and after different biochmical exams and differential culture bacteria recognized. Results & Conclusion: In antibiogram test, the bacteria was sensitive to Tetracycline, Cloramfenicol, Gentamycin and enrofloxasin . The fish breeder was advised to prevent entering stress factors to fish as possible as he can, and use oxytetracycline for 14 days in order to cure the sick fish. Benzalkonium sodium was used for water of the pool. After two weeks the fatalities were totally stopped.