Large scale mortality in cultured Nile tilapia (<i>Oreochromis niloticus</i>): natural co-infection with <i>Aeromonas hydrophila</i> and <i>Streptococcus iniae</i>.

Abstract

Background: Nile tilapia is a highly valuable fish in the aquaculture sector. A culture farm has reported heavy mortalities of tilapia. Aims: The present study aimed to identify the etiological agent responsible for the heavy mortality in cage cultured tilapia. Methods: The moribund and freshly dead fishes were analyzed for clinical signs. Biochemical and molecular characterizations were performed to identify the etiological agents of the disease. Also, polymerase chain reaction (PCR) assay was used to detect the presence of the virulence genes. The susceptibility of the isolates to various antibiotics was tested by the disk diffusion method. Results: led to increased mortality in tilapia. Histopathological changes were observed in the liver and spleen tissues of the co-infected fishes. Conclusion: .