Evaluation of a Trivalent Vaccine for Aeromonas hydrophila, Flavobacterium columnare, and Edwardsiella ictaluri Using In-pond Raceway Systems in West Alabama

Abstract

A trivalent vaccine, for virulent Aeromonas hydrophila, Flavobacterium columnare, and Edwardsiella ictaluri, was tested using in-pond raceway systems (IPRS) located in three active commercial catfish ponds. The goal of this study was to determine the effectiveness of this new vaccine against naturally occurring incidences of the target diseases. The study was conducted using three identical IPRS units in three ponds owned and operated by Williamson Cattle Company (WCC). Each IPRS was capable of housing four replicates per treatment. The fish were vaccinated in May and stocked into the raceways in June of 2017. At the time of stocking mean fish weight was 36.79 g per individual. The fish were harvested in September of 2018 and average individual weight and total weight was collected for each treatment. The average individual weights at harvest ranged from 715.9 g to 933.6 g. Survival ranged from 46.7 % to 65.2%. There were no significant differences among treatments for any of the production endpoints measured. A separate laboratory challenge trial was carried out with fish vaccinated via injection, as well as an equal amount of control fish. At the end of the field trial some of the vaccinated and control fish were transported to Auburn, AL for controlled laboratory disease challenges. Two challenge trials were conducted for each of the target diseases. A statistically significant difference in mortality rate was only found in one of the challenges using vAh bacteria. In that challenge, the vaccinated group had a 50 ± 16 percent mortality rate compared to the 95 ± 5.8 percent mortality rate of the control group (P < 0.0364).