INFECTIVITY AND PATHOGENICITY OF BACULOVIRUS PENAEI(BP) IN CULTURED LARVAL AND POSTLARVAL PACIFIC WHITE SHRIMP, PENAEUS-VANNAMEI, RELATED TO THE STAGE OF VIRAL DEVELOPMENT

The infectivity and pathogenicity of the penaeid shrimp virus, Baculov irus penaei (BP), is influenced by the stage of viral development. Thi s study consisted of a preliminary experiment which showed that nonocc uluded virus administered per os is infective, followed by two infecti vity experiments. In the first phase of each infectivity experiment, m ysis stage larvae of Penaeus vannamei were inoculated with BP and samp les of infected tissue were collected at various times postinoculation (p.i.). These samples were then used to inoculate either mysis or pos tlarval stage P. vannamei in the second phase of each experiment. Vira l inocula prepared from patently infected tissues consistently produce d infections in both mysis and postlarval stage shrimp. Inocula prepar ed from prepatently infected tissue collected 12-18 h p.i. produced in fections in some, but not all replicate cultures, while inocula prepar ed from tissues collected earlier than 12 h p.i. were not infective. V iral development in mysis stage larvae was substantially delayed and t he mortality was significantly lower when the viral inocula were prepa red from prepatently compared to patently infected tissues. BP appears to be most pathogenic to larvae that have been exposed to inocula pre pared from tissues that had recently developed a high prevalence of pa tent infections or about 72 h p.i. (C) 1998 Academic Press.