PICORNA-LIKE VIRUS-ASSOCIATED WITH MORTALITY AND A SPONGIOUS ENCEPHALOPATHY IN GROUPER EPINEPHELUS-MALABARICUS

A picorna-like virus was detected from diseased fry and fingerling gro uper Epinephelus malabaricus cultured in southern Thailand. Affected g rouper exhibited dark coloration of the head and tail, loss of equilib rium and corkscrew-like swimming. Pathological changes of affected fis h showed vacuolating encephalopathy and retinopathy. Intracytoplasmic inclusions were observed in the nerve cells. From electron microscopic studies, virus particles could be detected in the brain and eyeball o f affected fishes. They were round to icosahedral, without an envelope , 20 to 25 nm in diameter and had an electron dense core of 16 nm. Fil trates (0.45 mu m) of affected brain and eyeball tissues can produce t he same clinical signs in healthy grouper after injection, and the ide ntical virus particles could be observed in the brain and retina of ex perimentally infected fish.