Performing Department
(N/A)
Non Technical Summary
The catfish industry is the largest sector of U.S. aquaculture, with most production in Mississippi and west Alabama. Catfish producers face major disease issues due to bacterial pathogens, namely virulentAeromonas hydrophila(vAh),Edwardsiellaspp., and columnaris-causing bacteria (Flavobacteriumspp.). Most producers rely heavily on antibiotics to treat these diseases, which are costly and present an inherent risk of developing antimicrobial resistance over time, as the aquaculture industry is currently limited to just three options. There has been an increased interest in probiotic applications to reduce antibiotic dependency and enhance fish health. One such probiotic, AP193, demonstrates efficacy against vAh infection due to metabolite production of difficidin. Further, an inactivated, mutant vAh vaccine has been developed at AU and provides protection when administered via oral delivery. Applying these preventative and alternative approaches will provide producers with tools to combat on-farm vAh outbreaks, but we believe both approaches can be synergistically optimized. To accomplish this, our current project aims to: 1) Generate an optimized probiotic strain for enhanced metabolite production; 2) Evaluate a combination of probiotic + vaccine feeding to bolster protection in catfish and further explore the immune response using a tilapia oral gavage challenge model; and 3) Discern the cross-protective ability of these two approaches in protecting against different vAh clades in hybrid and channel catfish. This Special Research Grants for Aquaculture project will benefit catfish producers by providing preventative options for vAh management that can be administered at the pond level.
Animal Health Component
80%
Research Effort Categories
Basic
20%
Applied
80%
Developmental
(N/A)
Goals / Objectives
The team's project goals are to characterize probiotic and vaccination synergy in Alabama catfish production, develop mitigation strategies for catfish producers, and identify new means of controlling vAh at the farm level.Together, these approaches will provide the AL catfish industry with a scientific toolbox to assist in controlling the emergence of vAh.As such, we aim to:1.Generate a novel probiotic isolate for use in catfish culture as a health-promoting product.2.Discern an optimized feeding/vaccination regime using channel catfish and tilapia models.3.Evaluate the potential for this strategy to protect channel and hybrid catfish against infection with different vAh clades.
Project Methods
This two-year project centers around three primary objectives. The first will systematically optimize the AP193 probiotic isolate as a catfish feed additive. Objective 1 will result in an AP193 adapted for more rapid growth on the poorer quality catfish feed (28% protein), knowledge of the phenotypic and genotypic differences between the wild-type and adapted AP193 strains, and a stock of wild-type and adapted AP193 spores sufficient for the needs of the subsequent objectives.The second objective will critically investigate the combination of an attenuated vAh vaccine and probiotic to detail potential synergistic interactions. We will use a standard, reproducible vAh pathogen challenge model for catfish for external entry and an accompanying oral-gavage methodology in tilapia to elucidate pathogen-treatment interactions in the gastrointestinal tract. This objective will inform efficacy for the probiotic + vaccine, using both the standard vAh challenge model (fin-clip) and an "enteric-only" infection route in tilapia. This will provide insight intoin vivomortality, fish immune response, and changes in the gut microbiota.In Objective 3, we will evaluate the probiotic + vaccine combination in channel and hybrid catfish. Throughout the project, the team will focus on outreach to pass on the newfound knowledge from the project and promote the judicious use of antibiotics throughout the catfish industry.The cross-protection evaluation in channel and hybrid catfish will build upon our Objective 2 findings and evaluate the ability of the probiotic + vaccine combination to protect against both AL and MS vAh clades. We will also assess the IgM response to gauge protection levels before thein vivochallenge assessment.