Cross-protection efficacy of a live-attenuated Edwarsiella ictaluri vaccine against heterologous Edwardsiella piscicida isolates in channel and channel x blue hybrid catfish

Authors: LOPEZ-PORRAS, ADRIAN - Mississippi State University; GRIFFIN, MATT - Mississippi State University; WARE, CYNTHIA - Mississippi State University; Richardson, Brad; GREENWAY, TERRENCE - Mississippi State University; ROSSER, T - Mississippi State University; AARATTUTHODIYIL, SUJA - Mississippi State University; WISE, DAVID - Mississippi State University

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2022
Publication Date: 4/25/2022
Citation: Lopez-Porras, A., Griffin, M.J., Ware, C., Richardson, B.M., Greenway, T.E., Rosser, T.G., Aarattuthodiyil, S., Wise, D.J. 2022. Cross-protection efficacy of a live-attenuated Edwarsiella ictaluri vaccine against heterologous Edwardsiella piscicida isolates in channel and channel x blue hybrid catfish. Journal of Fish Diseases. https://doi.org/10.1111/jfd.13623.
DOI: https://doi.org/10.1111/jfd.13623

Interpretive Summary: The bacterium Edwardsiella piscicida is an increasingly detrimental issue for catfish aquaculture, particularly in hybrid catfish. Research has shown an attenuated E. ictaluri vaccine to be effect in protecting against at least one strain of E. piscicida; however, no it is unknown whether this protection extends to other E. piscicida strains collected from commercial catfish farms. Scientists at the USDA, ARS, Warmwater Aquaculture Research Unit and Mississippi State University in Stoneville investigated the cross-protective effects of the E. ictaluri vaccine against strains representing the five distinct genetic groups E. piscicida. The function significance of the genetic variability is currently unknown. The E. ictaluri vaccine resulted in greater than 80% survival against all E. piscicida strains in channel catfish, and greater than 55% survival against all strains in hybrid catfish. While survival was lower in hybrid catfish, the results of the study suggest shared virulent DNA between E. piscicida and E. ictaluri which could be exploited in future vaccine development.

Technical Abstract: Edwardsiella piscicida is a growing problem for catfish aquaculture in the southeastern United States, particularly in channel (Ictalurus punctatus) x blue (I. furcatus) catfish hybrids. Research has shown E. piscicida isolates recovered from farmed catfish in Mississippi form at least five discrete phyletic groups, with no apparent differences in virulence in channel and hybrid catfish. Laboratory trials have shown a live-attenuated E. ictaluri vaccine cross-protects against at least one E. piscicida isolate (S11-285) in channel and hybrid catfish, although it is unknown if this protection exists for other E. piscicida variants. To this end, channel and hybrid catfish were immunized by immersion with a live-attenuated E. ictaluri vaccine (340X2). Thirty days later, fish were challenged by intracoelomic injection with representative E. piscicida variants from each phyletic group. Relative percent survival (RPS) for hybrids ranged from 54.7-77.8%, while RPS in channels ranged from 80.5-100%. A second study investigated the inverse, with channel and hybrid catfish exposed by immersion with heterologous E. piscicida isolates representing each phyletic group. Thirty days later, fish were challenged by immersion with wild-type E. ictaluri isolate S97-773. Regardless of variant, previous exposure to heterologous E. piscicida isolates significantly improved survival during E. ictaluri challenge which is consistent with previous work. These findings indicate the presence of shared and conserved antigens among E. piscicida and E. ictaluri that could be exploited by polyvalent or cross-protective vaccines.