Abstract

A nodavirus was detected in the larval stages of red drum, Sciaenops ocellatus, from Korea. The fish suffered heavy mortality (80-90%) and the principal signs of the disease included darkening of the body, anorexia, whirling movement, spinal deformity and enlarged swim bladder. Histological findings revealed vacuolation and necrosis in the nerve cells of brain, spinal cord and retina. Electron microscopic observation showed the presence of spherical, non-enveloped viral particles, measuring 30 nm in diameter in the cytoplasm of nerve cells. Samples from dead and moribund fish were subjected to RT-PCR using SJNNV primers and a 426-bp product was detected by agarose gel electrophoresis. The results of the present investigation indicated that the causative agent of the outbreak was a nodavirus, and this forms the first record of NNV in red drum.