Cross‐protective potential of a live‐attenuated <scp><i>Edwardsiella ictaluri</i></scp> vaccine against <scp><i>Edwardsiella piscicida</i></scp> in channel (<scp><i>Ictalurus punctatus</i></scp>) and channel × blue (<scp><i>Ictalurus furcatus</i></scp>) hybrid catfish
Matt J. Griffin, Terrence E. Greenway, Todd S. Byars, Cynthia Ware, Suja Aarattuthodiyil, Ganesh Kumar, David J. Wise
Abstract
Abstract Edwardsiella piscicida has emerged as an important pathogen of channel × blue catfish hybrids cultured in the southeastern United States. With increasing popularity of hybrid catfish and growing concern over E. piscicida , the crossprotective potential of a live‐attenuated E.ictaluri vaccine was evaluated. An immunization bath of E. piscicida (3 × 10 7 CFU/ml) protected channel catfish against immersion challenge of wild‐type E. ictaluri (1 × 10 7 CFU/ml) across multiple temperatures and feeding regimens (relative percent survival [RPS]: 89–100%). Channel catfish immunized orally with a live‐attenuated E. ictaluri vaccine/feed admix (3 × 10 7 CFU/g of feed) were protected against intracoelomic injections of both high (HD) (7.4x10 5 CFU/fish; RPS = 85%) and low doses (LD) (1.5 × 10 5 CFU/fish; RPS = 88%) of E. piscicida . Because of limited feed consumption during vaccination, oral immunization of hybrids was followed by a 30‐min immersion bath with cultured vaccine (5 × 10 6 CFU/ml). Combinatory oral/bath vaccination was ineffective against HD E. piscicida but was protective against LD E. piscicida (48% RPS) and E. ictaluri (96% RPS). Finally, naïve catfish that survived LD E. piscicida injections were protected against E. ictaluri immersion challenge (2 × 10 7 CFU/ml; RPS: Hybrids 55%; Channels 75%). Results suggest a live‐attenuated E. ictaluri vaccine can also protect channel and hybrid catfish against E. piscicida .