Detection of red-spotted grouper nervous necrosis virus by loop-mediated isothermal amplification

Red-spotted grouper nervous necrosis virus (RGNNV) causes high mortality in marine fish larvae cultured in China. To control better an outbreak of this virus, a rapid, specific and sensitive detection method based on loop-mediated isothermal amplification (LAMP) was developed. A set of four primers, two outer and two inner, was designed from RGNNV genome RNA. The LAMP reaction mix was optimized. The method was specific as no cross-reaction was observed between white spot syndrome virus, koi herpesvirus, infectious spleen and kidney necrosis virus, mud crab reovirus, and grass carp hemorrhage virus. The sensitivity of LAMP was 100-fold higher than the nested PCR in detecting the presence of RGNNV. RGNNV was detected in the brain of Trachinotus ovatus that showed typical symptoms of NNV infection, with the standardized LAMP procedure.