Conventional identification of virus involves isolation of viral genome followed by nested PCR, DNA-based detection and symptomatic methods have the potential for widespread application of in aquaculture[17]. Efforts to overcome these problems have led to the development of immunoassay and DNA-based symptomatic methods, including fluorescent antibody tests (FAT), enzyme-linked immunosorbent assays( ELISA ) ,radioimmunoassay ( RIA ) , in situ hybridization(ISH), dot blot hybridization (DBH) and polymerase chain reaction (PCR) amplification techniques. The use of DNA-based methods derives from the premise that each species of pathogen carries unique DNA or RNA sequences that differentiate it from other organisms.