Protective effect of microbial immunostimulants and antiviral plants against WSSV in Litopenaeus vannamei cultured under laboratory conditions

The effect of a mixture of antiviral plants (Echinacea purpurea and Uncaria tomentosa) and microbial immunostimulants (Pediococcus parvulus and Candida parapsilosis) on growth performance, survival, white spot syndrome virus (WSSV) prevalence, and immune response of L. vannamei was evaluated under laboratory conditions. Powdered plants (PP) were included in the commercial feed pellet at 0.0, 1.0, 2.0, and 4.0gkgfeed^-1 and microbial immunostimulants (MI) were included at 0.0, 2.1, 4.2, and 8.4mgkgfeed^-1. A bioassay was conducted for 21days. Feed supplemented with PP and MI did not influence survival and shrimp growth. However, the prevalence of WSSV in shrimp with low viral load decreased from 100% in the control group to 0% in animals fed with the PP and MI mixture. Additives increased significantly the phenoloxidase activity but not hemocyte and superoxide anion amount. The PP and MI mixture, added to feed, has the potential to be used prophylactically as an antiviral against WSSV in cultured shrimp.