Isolation and Identification the Causative Agent of Bacterial Hepatitis in the Common Carp Cyprinus carpio (Linnaeus, 1758)

Abstract

The present study was conducted to isolate and diagnose the bacterial infection of liver of common carp fish, with investigated the histopathological changes in effected organs. 102 common carp fish were collected from fish farms located in the area of the Abbasia, Najaf, Iraq, During six month of experimental period extended from 1^st January to 1^st July of 2016. The experimental period of current study was divided into two periods (three month each), first period was started from 1^st January to 1^st April and the second period was started from 1^st April to 1^st July . liver samples were collected for bacterial isolation and identification, with histopathological examination. Pathogenic agents were isolated and identified by using culture media (Nutrient agar, Salmonella -Shigella agar, MacConkey agar , pseudomonas agar and EMB agar), biochemical tests and Api20 test for confirmation.Result of this study showed differences between the bacterial isolates in first period from bacterial isolates in second period. The results of bacterial isolates in the first period were (E.coli 23.5%, Enterobacter 21.6% and Aeromonashydrophila 7.8% for the months January, February and March ) , while results of the bacterial isolates in the second period were (E. coli 35.3%, klebseliaoxytoca 15.7%, Salmonella Spp 3.9%, Pseudomonas aeruginosa 7.8% , K.pneumonia 9.8%). Histopathological results show Vaculation, necrosis and nuclear condensation were observed in hepatocytes of effected livers. In conclusion, According to the results obtained in this study, we investigated that , the time period from April up to July pathogenic agent ratio was more than pathogens agent ratio that was isolated in the months of January, February and March.

Keywords: common carp, Bacterial disease ,Aeromonashydrophila, liver