Identification of white spot syndrome associated baculovirus (WSBV) target organs in the shrimp Penaeus monodon by in situ hybridization

Penaeus monodon non-occluded baculovirus III (PmNOB III) is a strain of white spot syndrome associated baculovirus (WSBV) isolated from diseased black tiger shrimp P. monodon. In order to identify the target organs of WSBV, the tissue sections of experimentally infected shrimp sampled at 0, 16, 22, 40, 52, and 64 h post-infection were hybridized in situ with PmNOB III DNA-specific probe labelled with digoxigenin. WSBV-positive cells were initially observed at 16 h postinfection in the stomach, gill, cuticular epidermis and hepatopancreas. At 22 h post-infection, the lymphoid organ, antennal gland, muscle tissue, hematopoietic tissue, heart, midgut and hindgut were found to be WSBV-positive. The nervous tissue and compound eyes did not have WSBV-positive cells until 40 h post-infection. Thus Various tissues from the mesoderm and ectoderm, such as connective tissue, epithelium, nervous tissue and muscle, can all be infected by WSBV. By 52 or 64 h post-infection, it was found that the stomach, gill, cuticular epidermis, lymphoid organ, hematopoietic tissue and antennal gland were all heavily infected with WSBV and that these tissues had become necrotic. The white spot syndrome itself first appeared at 40 h post-infection, and the shrimp began to die al 64 h post-infection. The probe demonstrated no reaction to WSBV-negative tissue.