Susceptibility of Fish Species Cultured in Mangrove Brackish Area to Piscine Nodavirus

Abstract

Susceptibility of orange-spotted grouper Epinephelus coioides, Asian sea bass Lates calcarifer, mangrove red snapper Lutjanus argentimaculatus, milkfish Chanos chanos, and rabbitfish Siganus guttatus to piscine nodavirus from orange-spotted grouper was studied by experimental infection. The fish were intraperitoneally injected with 0.05 mL of the filtrate homogenate of infected organs from diseased grouper at 10 6.8 , 10 5 8 or 10 4 .TCID 50 /fish, while the control group received 0.05 mL of Hanks' balanced salt solution. Clinical signs such as lethargy, anorexia and darkened pigmentation were observed in the orange-spotted grouper, Asian sea bass, mangrove red snapper, and milkfish injected with high and medium doses of the homogenate. Although no or little mortality occurred in the experimentally-infected fish 10 days post-inoculation, viral nervous necrosis specific lesions such as severe necrosis and vacuolation in the brain and retina were produced in these four fish species. The virus was reisolated in SSN-1 cells inoculated with the filtrated tissue homogenate of survivors in all doses for all four fish species. However, in the experimentally infected rabbitfish no histological lesion was observed, and no virus was reisolated. These results indicate that grouper, sea bass, mangrove red snapper, and milkfish are susceptible to the piscine nodavirus isolated from diseased grouper.