Detection of white-spot syndrome in cultured penaeid shrimp in Asia: Microscopic observation and polymerase chain reaction

Serious disease outbreak caused by a new virus has been occurring among cultured penaeid shrimps in Asian countries since 1993. Typical signs include white spots or patches on the inner surface of the shell and carapace and/or reddish coloration of the body. Histopathological changes observed among diseased shrimps collected from various countries exhibited widespread cellular degeneration and severe nuclear hypertrophy in cells of most tissues derived from ectodermal and mesodermal origin. Similar rod-shaped to elliptical virus particles of various sizes of 70-120 nm x 240-340 nm surrounded by typical trilaminar envelope were found in the hypertrophied nuclei of affected cells. This virus was tentatively classified as a member of genus non-occluded baculovirus (NOB) of the subfamily Nudibaculovirinae of Baculovirus. A portion of the sequences of specific DNA fragment of an isolate from Thailand was used as a primer and compared to the other isolates collected from various countries. Results indicate that closely related strains of putative baculovirus were the causative agent of the white-spot syndrome of cultured penaeid shrimps occurring in six Asian countries. (C) 1998 Elsevier Science B.V. All rights reserved.