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ARS Home » Research » Research Project #431885

Research Project: Reducing Impacts of Disease on Salmonid Aquaculture Production

Location: Office of The Director

Project Number: 5090-31320-004-000-D
Project Type: In-House Appropriated

Start Date: Nov 7, 2016
End Date: Dec 31, 2019

Major impediments to production and profitability of U.S. aquaculture are the lack of genetically-defined species with traits for faster growth, greater feed efficiency/utilization, and improved disease resistance. Rainbow trout are important recreational and food fish species in the Great Lakes and it is thus important to improve productivity of this species in this region. Over these next 3 years we will focus on the following three Objectives and their supporting Sub-Objectives: Objective 1: Characterize mechanisms of innate immune response, and pathogen virulence, to control rhabdoviral diseases in salmonid aquaculture. • Sub-Objective 1.A.: Identify domains within viral proteins of infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicemia virus (VHSV) that interfere with the host virus recognition and response pathways in vitro. (Leaman, Stepien and Vakharia) • Sub-Objective 1.B.: Characterize the in vitro replication of recombinant IHNV and VHSV containing mutations designed to disrupt viral suppression of host recognition and response pathways. (Leaman and Vakharia) • Sub-Objective 1.C.: Assess the impact of IHNV and VHSV infection and subsequent innate immune suppression on the activation of dendritic cells (DCs). (Spear) • Sub-Objective 1.D.: Develop in vivo IHNV and VHSV challenge models in rainbow trout. (Spear and Shepherd) Objective 2: Use genetic techniques to characterize mechanisms of Flavobacterium virulence and identify potential strategies to control bacterial disease in salmonid aquaculture. • Sub-objective 2.A.: Develop genetic techniques for F. columnare strains that cause columnaris disease in rainbow trout. (McBride) • Sub-Objective 2.B.: Isolate and characterize F. columnare mutants and identify virulence factors associated with ability to cause disease in rainbow trout. (McBride) • Sub-Objective 2.C.: Develop improved genetic techniques for F. psychrophilum, the causative agent of bacterial coldwater disease. (McBride) Objective 3: Measure and modulate antimicrobial peptides (AMPs) as a means to control disease in salmonids. • Sub-Objective 3.A.: Characterize the environmental and endocrine contributions to regulation and expression of AMPs in rainbow trout. (Shepherd and Spear) • Sub-Objective 3.B.: Test the anti-viral and anti-bacterial activities of two synthetic trout AMPs in vitro. (Shepherd, Spear, Leaman and McBride)

For Objective 1: We will characterize the mechanisms of virulence for Viral Hemorrhagic Septicemia virus (VHSV) and Infectious Hematopoietic Necrosis virus (IHNV) in rainbow trout. Research will involve molecular analysis of viral diversity, mutational analysis of viral factors contributing to virulence in rainbow trout. These studies will utilize homologous in vitro systems (cell-lines and dendritic cells) to identify of host factors involved in recognition and response pathways to viral infection in rainbow trout. Lastly, disease challenge assays will be developed, and validated, to understand the virulence and the disease processes for IHNV and VHSV pathogens in rainbow trout. For Objective 2: This work will target mechanisms of pathogenesis of F. psychrophilum (causative agent in bacterial cold water disease) and F. columnare (causative agent in columnaris disease) in rainbow trout. To do this, we will use bacterial culture and genetic techniques to isolate mechanisms of pathogensis for Flavobacterium spp. in this species. Attenuated bacterial strains will be evaluated for pathogenesis using established disease challenge models, in this species. For Objective 3: We will characterize the physiological regulation of antimicrobial peptides (AMPs) and their actions in rainbow trout. To accomplish this, we will assess how environmental stressors, and hormones, affect expression (genes) and levels (proteins) of AMPs in this species. Additionally, we shall utilize in vitro techniques to evaluate biocidal actions of select AMPs against VHSV and IHNV and Flavobacterium spp.