S Mehdizadeh Mood - Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran
M Soltani
H Ebrahimzadeh Mousavi
H Bagheri

Objective: Bacterial disease is the most common infectious problem of ornamental fishes, and most bacterial infections are caused by gram-negative organisms. Extrinsic stressors, including shipping, crowding, poor water quality, and inadequate nutrition, may predispose an ornamental fish to bacterial disease. High mortality rate in one of the importing ornamental fish farms in Tehran was occurred in June 2008. To recognize the reason 50 samples of fishes with clinical sign including anorexia, exophthalmia, hyperemia and hemorrhage in skin and fins associated with fin rot and erosion in some cases were taken to the lab. Method & Materials: 50 live clinically affected fish were examined. At first wet smear was prepared and investigation for parasitic infestation was continued under the light microscope. Then samples were taken to the aquatic microbiological lab .Gram–staining , Bacterial culture and biochemical tests for bacterial examination were performed. Results & Conclusion: In wet smear 1-3 Gyrodactylus sp. were observed. However, based on the clinical signs and high mortality, such light infestation could not have been a probable cause. In necropsy, there were fluid in abdominal cavity with hyperemia in internal organs and necrosis. The bacterial culture indicated the presence of Aeromonas bacteria and biochemical results demonstrated that the species was A. hydrophila. Reducing the number of fish per litre, more frequent water change and addition of Oxytetracycline (50 to 75 mg/kg of fish for 10 days) which has been the drug of choice for treating motile aeromonad septicemias in fishes were recommended for considerable reduction of mortality rate.

Bacteria, ornamental fish, Aeromonas hydrophila, septicemia