Detection of betanodavirus in wild caught fry milk fish, Chanos chanos , (Lacepeds 1803)

Betanoda virus was detected in wild caught milk fish fry ( Chanos chanos ) exhibiting Beta noda virus was detected in wild caught milk fish fry ( Chanos chanos ) showing typical clinical symptoms and signs of viral nervous necrosis (VNN)/ Viral encephalopathy and retinopathy, (VER) from the bank of Matchlipattinam, Andhra Pradesh, India during March 2014. Mortality of these fry was observed within a few days after stocking and attained 100 % in next few days. The larvae infected by the virus showed typical swimming behavior which included positioning in a vertical manner with a whirling type movement; sinking to the bottom, darting or swimming in a corkscrew fashion; belly-up at rest, abnormal body coloration (pale or dark) and over inflation of swim bladder. Severe pathological changes in the form of vacuolation and necrosis in brain and other organs such as spinal cord, and retina of the eyes further confirmed the infection by this virus. The earliest occurrence of diseases was less than 30 days of post-hatch, less than 35 mm total length. Usual mortality rate varied from 50-80 % with highest mortality rate up to 100 % in wild caught milk fishes. Amplification of the virus RNA2 region by RT-PCR of Beta noda virus yielded a product of 430 bp .