Betanodavirus infection in reared marine fishes along the Arabian Gulf

Betanodavirus or nervous necrosis virus (NNV) is responsible for viral nervous necrosis (VNN) of fishes and is associated with mass mortalities of various fish species throughout the world. Here, we report for the first time Betanodavirus infection in Arabian Gulf region of the Kingdom of Bahrain. The present study is also the first report of mortality due to NNV infection in sobaity seabream Sparidentex hasta. NNV was detected in reared fry of gilthead seabream Sparus aurata and adults of sobaity seabream and brown-spotted grouper Epinephelus chlorostigma using nested PCR. In the present study, the rearing unit recorded 100% mortality in fry of gilthead seabream and 24 and 63% mortalities were recorded in different age groups of adult sobaity seabream due to VNN. Classical clinical signs of VNN such as body discoloration, loss of appetite and abnormal swimming behaviour were observed in fry of gilthead seabream. Histopathological studies revealed characteristic vacuolation and degeneration of brain and ocular tissues of sobaity seabream. However, brown-spotted grouper carried subclinical NNV infection, and there was no mortality in the group. Sequencing of nested PCR products and real-time PCR further confirmed the presence of the virus.