INFECTION OF THE YELLOW HEAD BACULO-LIKE VIRUS (YBV) IN 2 SPECIES OF PENAEID SHRIMP, PENAEUS-STYLIROSTRIS (STIMPSON) AND PENAEUS-VANNAMEI (BOONE)

Yellow head baculo-like virus infection and disease were demonstrated experimentally in the two main species of penaeid shrimp cultured in Hawaii and the Western hemisphere. Viral infection was induced by intramuscular inoculation of a 10% suspension of cephalothorax tissue filtrate prepared from two tiger shrimp, Penaeus monodon Fabricius, infected with yellow head disease, into sub-adult (3-10g) P. stylirostris (Stimpson) and P. vannamei (Boone). Signs of disease appeared as early as 2 days post infection (p.i.), and in most cases mortality reached 100% within 5-7 days p.i. Histopathological examination of the infected animals revealed extensive cellular necrosis in ectodermal and some mesenchymal tissues. Electron microscopical examination of thin sections of the gill and hepatopancreas from the infected shrimp revealed non-occluded rod-shaped baculo-like virus particles measuring 130-197 x 45-58nm which were primarily localized within the cytoplasm of infected cells. The virus particles were contained within cytoplasmic vacuoles, and occurred singly or in small groups of two or more particles.