Development for control methods for factors suppressing sustainable production of aquaculture species: Experimental transmission of piscine nodavirus-induced viral nervous necrosis to the orange-spotted grouper Epinephelus coioides

Abstract

Viral nervous necrosis (VNN) of larval orange-spotted grouper Epinephelus coioides has been recorded recently in the Philippines. The present study describes the pathogenicity of a piscine nodavirus (betanodavirus), the causative agent of VNN. Healthy orange-spotted grouper were challenged by intraperitoneal injection of the filtered tissue homogenate of VNN-diseased grouper. Abnormal swimming behavior, mortality, and necrosis and vacuolation of the brain and retina which are characteristics of VNN were reproduced in experimentally infected fish. Electron microscopic observations revealed that virus particles were present in the cytoplasm of the brain and retina; they were round in shape, without an envelope, 20 to 25 nm in diameter. The virus was reisolated from SSN-1 cells inoculated with the filtered tissue homogenate of survivors of all experimental doses. These results indicate that a piscine nodavirus from the orange-spotted grouper is the causative agent of mass mortality of this species in the Philippines.