** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** 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.