Experimental infection of white spot baculovirus in some cultured and wild decapods in Taiwan

Techniques for the detection of white spot baculovirus virus (WSBV) by polymerase chain reaction are well established. In this study, two primer sets designed from an isolate of WSBV from Penaeus monodon, PmNOB III, were used to detect WSBV infection in cultured and wild decapods in Taiwan. WSBV positive cases were found in all of four major marine cultured shrimp, P. monodon, P. japonicus, P. penicillatus and Metapenaeus ensis. Wild P. semisulcatus was also found to be naturally infected by WSBV. On the other hand, no cases of naturally occurring WSBV infection have yet been found in the wild shrimp Exopalaemen orientalis (from a milkfish culture farm), Trachypenaeus curvirostris, M. ensis (from the coast of Taiwan), Macrobrachium sp. and Procambarus clarkii (from rivers in Taiwan). Furthermore, neither the wild crabs, Calappa lophos, Portunus sanguinolentus, Charybdis granulata and C. feriata, nor the wild lobsters Panulirus ornatus, P. versicolor, P. longipes and P. penicillatus, collected from the coast of Taiwan showed any evidence of being naturally infected by WSBV. When captured specimens of these decapods were artificially infected by feeding them with tissues from severely PmNOB III infected P. monodon, wild shrimp mortality reached moderate to high levels at 18 days post infection. Using PCR analysis, WSBV DNA could be detected in the moribund specimens during the experimental period and in the survivors on the final day of the experiment. The mortalities in wild crabs and lobsters, however, were not significantly different from control groups. Nevertheless, WSBV DNA was also detectable in these specimens. WSBV was thus shown to have a wide host range and to exhibit different infectivity in the various decapods investigated in the present study.