LYMPHOID ORGAN VIRUS OF PENAEUS-MONODON FROM AUSTRALIA

Subadult Penaeus monodon shrimp were sampled from 4 farms in Queenslan d, Australia. Histological observations on lymphoid organs showed the formation of abnormal cell foci, which resembled tubules lacking a cen tral hemolymph vessel. These formations contained hypertrophied nuclei with marginated chromatin, vacuolated cells and inclusion bodies whic h stained positive with Feulgen's reaction. Male and female P. monodon broodstock were sampled from 1 farm and showed the same abnormal hist ological features within the lymphoid organ as the subadults. Electron microscopy revealed tightly enveloped, cylindrical particles, 163-200 nm x 36-63 nm, packed into paracrystalline arrays within the cytoplas m and infrequently within the nucleus. Arrays of virions were also obs erved within the cytoplasm of broodstock gill cells. Cross-sections of the particles revealed electron dense nucleic acid cores and envelope s. Nucleocapsids, 83-590 nm x 13-15 nm, were seen free and in vesicles within the cytoplasm. A negatively stained preparation of partially p urified lymphoid organ revealed a nucleocapsid with one conical end. L ymphoid organ virus (LOV) resembles yellow-head virus (YHV) from Thail and in its morphology and cytopathology and rhabdovirus of penaeid shr imp (RPS) from the Americas in its cytopathology.