BACILLIFORM VIRUS-INFECTION IN CULTURED CHINESE SHRIMP, PENAEUS-ORIENTALIS, IN CHINA

Outbreak of an epidemic disease has resulted in large-scale mortalitie s in cultured Chinese shrimp, Penaeus orientalis, in China since 1993, Histological examination of affected gills, stomach, midgut, hepatopa ncreas, heart, abdominal muscles, and lymphoid organ revealed degenera ted cells with hypertrophied nuclei stained homogeneously with hematox ylin in necrotic tissues, Electron microscopic examination showed rod- shaped, double-enveloped, and nonoccluded virus particles in the affec ted organs, An average size of the complete virion was 107 nm in diame ter and 365 nm in length; the size of the nucleocapsid was 75 nm in di ameter and 310 nm in length. From challenge tests by injection and fee ding with purified virus obtained from spontaneously diseased shrimp, it was demonstrated that the bacilliform virus was the causative agent of the disease.