Isolation and Characterization of Some Pathogenic Agents Causing Wobbling Syndrome in Cultured Oreochromis niloticus

Document Type : Original Article

Authors

1 Microbiological unit, Fish Diseases Department, Animal Health Research Institute, Agriculture Research Center, Dokki, Giza, Egypt.

2 Parasitological unit, Fish Diseases Department, Animal Health Research Institute, Agriculture Research Center, Dokki, Giza, Egypt.

Abstract

It is the first study all over Egypt which is dealing with fish swimming abnormalities influenced by mixed pathogens. A total of 160 Oreochromis niloticus were collected from some private fish farms at Sharkia governorate during the period from January to December 2008. Fish through isolation and characterization of some pathogenic agents were classified according to these groups: - A-Normal group: Free from any pathogenic agent. B-Bacterial infected group: Four bacterial isolates recovered from gas bladder affection of O.niloticus were Flavobacterium columnare, Pseudomonas fluorescens, Vibrio harveyi, and Staph aureus. Fish infected with bacteria showed up-right position or swim on its lateral sides. C-Mycotic infected group: Gas bladder infected with Ichthyophonus hoferi showed thick walled multinucleated cysts present near blood vessels confirmed by isolation in MEM containing 10% foetal bovine serum. D-Parasitic infected group: Gas bladder infected with Goussia cichlidarum showing white nodules variable in size contain fragile walled oocysts, have four sporocysts with two sporozoites, identified by the morphometry. E-Wobbling group: Etiological agents of the wobbling syndrome were coccidian parasite G. cichlidarum, I. hoferi and a strain of F. columnare. In-vitro sensitivity test of isolated bacterial strains to different chemotherapeutic agents was conducted to determine the effective antibiotics against isolated bacteria. No treatment is known to I. hoferi infected fish. Treatment of O. niloticus group infected with parasitic G. cichlidarum by Mirazid has been tried with great success. The present study has succeeded in isolation, identification and characterization of some significant pathogenic agents dealing with parasitic, bacterial, and mycotic groups which act as the causative agents of wobbling disease and shed light on ignored diagnosis of wobbling disease in Egypt cultured tilapia.

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