White spot baculovirus WSBV. is the causative agent of a disease which decimated some
cultured penaeid shrimp populations and inflicted severe economic damage in Taiwan. Until very
recently, the giant freshwater prawn Macrobrachium rosenbergii was thought to be unaffected by
this virus, but now signs closely resembling white spot syndrome WSS. have been observed on
its exoskeleton. In this paper, WSBV was established as the causative agent by using the
diagnostic polymerase chain reaction PCR. with WSBV-specific primers. WSBV was found in
M. rosenbergii larvae, postlarvae, juveniles, and adults. The amplified product from the DNA of
the naturally-infected WSS M. rosenbergii was similar to that of WSBV-infected Penaeus
monodon. Furthermore, comparison of the restriction profiles of these two PCR products by
HaeIII, HpaII, RsaI, and Sau3AI revealed no differences, suggesting that WSBVs from the
infected P. monodon and M. rosenbergii are closely related, if not identical. A homogenate
positive in one-step WSBV diagnostic PCR was prepared from frozen P. monodon for the
challenge experiment. Dilutions were added to tanks of healthy M. rosenbergii larvae and
postlarvae. After 2 days, some of the dead specimens were positive for WSBV by diagnostic PCR.