Application of gene probes to determine target organs of a penaeid shrimp baculovirus using in situ hybridization

Gene probes developed to the penaeid shrimp virus, Baculovirus penaei (BP), were utilized to determine the target organs infected by BP. BP-DNA fragments were nonradioactively labelled with digoxigenin and used to probe paraffin-embedded, fixed tissue sections using an in situ hybridization assay system. BP-infected tissue sections were microscopically examined for a blue-purple probe precipitate indicative of a positive reaction for BP. Particular attention was given to the reproductive tissues of mature shrimp, to determine if vertical transmission might occur. BP positive cells were located only in the hepatopancreatic tubule epithelium and in the midgut mucosa. These findings indicate that BP is a gut-infecting baculovirus that is transmitted horizontally by the per os route and not by true vertical transmission routes.