Susceptibility of delta select and delta control channel catfish lines to experimental Edwardsiella ictaluri and Edwardsiella piscicida infection

Authors: Bosworth, Brian; KOSHY, MANOJ CHANDY - Mississippi State University; WARE, CYNTHIA - Mississippi State University; YAMAMOTO, FERNANDO - Mississippi State University; BYARS, TODD - Mississippi State University; GRIFFIN, MATT - Mississippi State University; WISE, DAVID - Mississippi State University

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2024
Publication Date: 4/11/2024
Citation: Bosworth, B.G., Koshy, M., Ware, C., Yamamoto, F., Byars, T., Griffin, M., Wise, D. 2024. Susceptibility of delta select and delta control channel catfish lines to experimental Edwardsiella ictaluri and Edwardsiella piscicida infection. North American Journal of Aquaculture. https://doi.org/10.1002/naaq.10338.
DOI: https://doi.org/10.1002/naaq.10338

Interpretive Summary: The mission of the Warmwater Aquaculture Research Unit (WARU), USDA-ARS is to develop genetically improved catfish lines for release to U.S. catfish producers. The Delta Select channel catfish line has been selected for increased growth rate and meat yield and has been released to the industry. Selection continues for improved growth and meat yield in the Delta Select line, but WARU researchers are interested if selection for growth and carcass yield has altered performance for other important traits, including disease resistance. The bacterial pathogens Edwardsiella ictaluri and Edwardsiella piscicida cause significant mortalities in farmed-raised catfish. The Delta Select line was compared with the Delta Control line (an unselected line of catfish from the same base population as the Delta Selects) for survival following exposure to these two pathogens to determine if selection for increased growth and carcass yield had affected disease resistance in the Delta Select line. Delta Select and Delta Control line catfish had similar levels of mortalities following expousre to E. ictaluri, while the Delta Select line had about 15% higher survival than the Delta Controls following exposure to E. piscicida. The results of this study show that selection for increased growth and carcass yield in did not negatively impact resistance to E. ictaluri, and appears to have increased resistance to E. piscicida in the Delta Select line of channel catfish.

Technical Abstract: The Delta Select line of channel catfish (Ictalurus punctatus) was established in 2006 and has undergone five generations of genetic selection, specifically targeting increased growth rate and carcass yield and was released to U.S. catfish farmers in 2020. While improvements in growth rate and carcass yield have been confirmed, performance for other important production traits have yet to be evaluated. Infectious disease, particularly bacterial infections caused by Edwardsiella spp., cause significant economic losses to catfish producers in the southeastern United States. Given the economic consequences of these bacterial pathogens, experimental infectivity trials were conducted, comparing susceptibility to Edwardsiella spp. between the Delta Select line and a randomly bred line of channel catfish originating from the same base population (Delta Control line). Twenty-six full-sib families from each line were used in infectivity trials consisting of a high and a low dose of E. ictaluri (Immersion challenge; High dose: 1.6×107 CFU/ml; Low dose: 8.0×106 CFU/ml) and E. piscicida (Intracoelomic challenge; High dose: 6.3×105 CFU/fish; Low dose: 1.9×105 CFU/fish). The highest challenge dose resulted in the highest mortality for both pathogens, regardless of selection line. There was no significant difference in cumulative percent mortality between the Delta Select and Delta Control lines following the E. ictaluri challenge at either the high (p = 0.23) or low dose (p = 0.38). Delta Selects had reduced mortality (p <0.01) in response to E. piscicida challenge compared to the Delta Controls, regardless of dose. These results indicate selection for increased growth rate and carcass yield in the Delta Select channel catfish line did not negatively impact resistance to E. ictaluri, while potentially improving resistance to E. piscicida.