In contrast, a low dose
of WSSV-Viet capable of causing mortality in P. vannamei resulted in no detectable infection in M.
rosenbergii. Mean prawn infectious dose 50% endpoints (PID50 ml-1) determined in M. rosenbergii
were in the order of 100-fold higher for WSSV-Thai-1 (105.3±0.4 PID50 ml-1) than for WSSVViet
(103.2±0.2 PID50 ml-1), with each of these being about 20-fold and 400-fold lower, respectively,
than found previously in P. vannamei. The median lethal dose (LD50 ml-1) determined in M. rosenbergii
was also far higher (~1000-fold) for WSSV-Thai-1 (105.4±0.4 LD50 ml-1) than for WSSV-Viet
(102.3±0.3 LD50 ml-1). Based on these data, it is clear that juvenile M. rosenbergii are susceptible to
WSSV infection, disease and mortality. In comparison to P. vannamei, however, juvenile M. rosenbergii
appear more capable of resisting infection and disease, particularly in the case of a WSSV
strain with lower apparent virulence.