Reo-Like Virus in White Shrimp Penaeus vannamei (Crustacea: Decapoda): Co-occurrence with Baculovirus penaei in Experimental Infections

A virus, tentatively identified as reo-like, occurred concurrently with experimentally-induced Baculovirus penaei (BP) infection in cultured white shrimp larvae Penaeus vannamei. Each shrimp with a reo-like viral infection also had a BP infection, but not all BP-infected shrimp had a reo-like infection. Both viruses occurred in the same tissues and occasionally withln the same cell. The reolike virus developed in epithelial cells of the anterior midgut and in reserve- and fibrillar-cells of the hepatopancreas. The paraspherical and non-enveloped reo-like virions (ca. 50 nm diam.) occurred as unordered aggregates in the cell cytoplasm. Their etiology has not been determined. Reo-like virions may have been introduced along with the BP virus, or, were latent and only manifested due to stress induced by the more pathogenic BP virus.

Relationship Between BP (Baculovirus penaei) Energy Reserves in Larval and Postlarval Pacific White Shrimp Penaeus vannamei

The relationship between energy reserves of the penaeid shrimp Penaeus vannamei and Baculovirus penaei, or BP, were investigated in a series of experiments using mysis stage or early postlarval shrimp. Pre-exposure and post-exposure levels of protein and triacylgycerol (TAG) were determined. The effect of pre-exposure protein and TAG levels on susceptibility to BP infections was also investigated by starving a group of shrimp immediately prior to BP exposure. There was no consistent relationship between either pre-exposure or post-exposure protein levels and the percent of shrimp developing patent BP infections. There was, however, a significant positive correlation between TAG levels immediately prior to viral exposure and prevalence of infection 72 h later. Experimental reduction of TAG reserves prior to BP exposure delayed the development of a patent infection. In some, but not all, experiments there was a significant reduction in TAG levels of infected compared with uninfected shrimp 72 h post-exposure. The effect of patent BP infections on host TAG levels was subordinate to fluctuations in TAG content associated with the ontogeny of the hepatopancreas. Results of this study support histological observations that shrimp lipid levels can be altered by baculovirus infections. Furthermore, high levels of energy reserves in the form of TAG are associated with increased susceptibility to BP infection in larval and postlarval shrimp.