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 H awaii and the Western hemisphere. Viral infection was induced by intra muscular inoculation of a 10% suspension of cephalothorax tissue filtr ate prepared from two tiger shrimp, Penaeus monodon Fabricius, infecte d with yellow head disease, into sub-adult (3-10g) P. stylirostris (St impson) 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 a nimals revealed extensive cellular necrosis in ectodermal and some mes enchymal tissues. Electron microscopical examination of thin sections of the gill and hepatopancreas from the infected shrimp revealed non-o ccluded rod-shaped baculo-like virus particles measuring 130-197 x 45- 58nm which were primarily localized within the cytoplasm of infected c ells. The virus particles were contained within cytoplasmic vacuoles, and occurred singly or in small groups of two or more particles.