University of Maine - Cooperative Extension Aquatic Animal Health Lab and Aquaculture Research Institute
University of Maine - Cooperative Extension Aquatic Animal Health Lab and Aquaculture Research Institute
1Amber E. Johnston, 1Deborah A. Bouchard, 1Sarah M. Turner, 2Demitri Lifgren, 2Mark P. Polinski
1University of Maine Cooperative Extension, Aquaculture Research Institute, Aquatic Animal Health Laboratory, 17 Godfrey Drive, Orono, ME 04473; 2United States Department of Agriculture – Agricultural Research Service, National Cold Water Marine Aquaculture Center, 25 Salmon Farm Way, Franklin, ME 04634
For over 20 years, the National Cold Water Marine Aquaculture Center (NCWMAC) has selectively bred Atlantic salmon for improved aquaculture performance including increased growth and sea lice resistance. In this study, we sought to determine if these selective breeding approaches have incidentally affected fish susceptibility to infectious salmon anemia virus (ISAV) and/or resistance to its associated commercially impactful disease – infectious salmon anemia (ISA). We further sought to investigate if variations in family-based resistance to ISAV and/or ISA could be used to identify mechanisms for generating a resistant salmon phenotype. To do this, 40 families (30 selectively bred for aquaculture production and 10 reference control families) were first divided into 16 replicate tanks for family survival analyses with one salmon per family per tank. Four fish per family were exposed to ISAV via intraperitoneal injection (104 TCID50ml-1) while the remaining fish per family were exposed by cohabitation. Additionally, four tanks each containing one fish per family were exposed via cohabitation with ISAV injected mixed-family-origin fish and utilized for periodic tissue sampling. Survival analyses revealed no significant difference in outcome between injected or cohabitated fish; yet cumulative mortality across the 40 families ranged from 25 to 94%, with significant differences observed between the most and least susceptible families. Survival analyses also revealed no difference in mean survival between selectively bred and control families, suggesting that current NCWMAC selective breeding approaches have not incidentally impacted ISAV resistance. Further, RT-qPCR screening identified viral loads in the spleen to be consistently as high or higher relative to gill, heart, or kidney of infected fish, and that these loads were not lower in fish of resistant families compared to susceptible families. This data, in concert with the observation that disease timing (although not outcome) was similar between resistant and susceptible families, suggests that phenotypic resistance may be decided later in the infection process and involves mechanisms that enhance host damage control processes rather than suppressing viral replication. Future research will focus on transcriptome mapping of fish from resistant versus susceptible families for better determining the pathways involved in establishing an ISAV resistant phenotype.
1,2Daniel DeLap, 1,3Sarah M. Turner, 1,3Deborah Bouchard
1University of Maine Aquaculture Research Institute; 2University of Maine School of Marine Science; 3University of Maine Cooperative Extension
Infectious Salmon Anemia Virus (ISAV), belonging to the Orthomyxoviridae family, consists of eight negative single-stranded RNA segments and is the causative agent of infectious salmon anemia (ISA), a serious disease of Atlantic salmon (Salmo salar L.). ISA can cause significant mortalities of up to 90% in infected aquacultured Atlantic salmon . ISAV can be classified into two subtype groups, a highly virulent HPR-delete variant and avirulent non-delete variant (ISAV-HPR0). Whether or not avirulent HPR0 leads to virulent HPR-delete remains in question. Understanding the dynamics between these two variants could play a vital role in helping to control disease outbreaks caused by ISAV-delete and thus lead to a more economically sustainable Atlantic salmon aquaculture industry. One major hurdle to better understanding the role that ISAV-HPR0 plays in virulence and disease is due to the inability to propagate and amplify ISAV-HPR0 in cell lines. Because ISAV-HPR0 appears to mainly target Atlantic salmon epithelial gill cells, a method for culturing primary gill cells from Atlantic salmon was developed. In repeated trials, 100% confluency was obtained in 25cm2 cell culture flasks but subculture of these cells was not achieved. Establishing Atlantic primary gill cell lines could lead to amplification of ISAV-HPR0 for further investigation of the relationship between virulent HPR-delete and avirulent HPR0. With the ability to culture primary gill cells, continued research aims at preparing primary gill cells from Atlantic salmon that have tested positive for ISAV HPR0 to determine if amplification of the viral agent can be achieved in these cells.
Best presentation award winner
1Sarah Turner, 1Michael Mason, 1Deborah Bouchard
1Aquaculture Research Institute; University of Maine; Orono, ME 04468
Disease outbreaks are a major impediment to aquaculture production and are forecasted to continue as the industry grows and the climate warms. Vaccines are integral for disease management in aquaculture but they can be expensive, vary in effectiveness, and come with adjuvant-induced adverse effects causing fish welfare issues and negative economic impacts. The goal of this interdisciplinary project is to develop a new generation of vaccines for sustainable aquaculture. Our project uses novel nanomaterials produced from renewable wood fiber as depots/adjuvants in vaccine formulations to modulate the immune response of Atlantic salmon in a biocompatible, environmentally friendly, and cost-effective manner. Our interdisciplinary research team is elucidating the role of cellulose nanomaterials (CNM) as a vaccine depot and mobile immunostimulant, the extent of CNM migration in vivo, and the efficacy of CNM bound antigen as an immunostimulant for protection against two Atlantic salmon pathogens. To accomplish this, we have prepared and conducted in vitro characterizations of tuned CNM hydrogels and CNM/antigen (vaccine) formulations structurally, chemically, and mechanically of CNM variants (CNM) and in vivo migration using histopathology. Additionally, we assessed safety/toxicity and immunogenicity of CNM hydrogel formulations in vivo as a vaccine depot in Atlantic salmon by quantifying the antibody kinetics in vaccinated fish serum using enzyme-linked immunosorbent assays and gene expression. The next phase of our work will involve conducting in vivo studies to evaluate the efficacy of the CNM vaccine(s) in protecting against Aeromonas salmonicida in Atlantic salmon by performing a pathogen challenge study. Our results to date will be reported and discussed.