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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #425309
Research Project: Maximizing Profitability and Fish Health in Catfish Aquaculture

Location: Warmwater Aquaculture Research Unit

Title: Coinfection of channel catfish (Ictalurus punctatus) with virulent Aeromonas hydrophila and Flavobacterium covae exacerbates mortality

Author
item WISE, ALLISON - Auburn University
item LAFRENTZ, BENJAMIN - USDA-ARS Sino-american Biological Control Laboratory
item KELLY, ANITA - Auburn University
item LILES, MARK - Auburn University
item GRIFFIN, MATT - Mississippi State University
item BECK, BENNJAMIN - USDA-ARS Sino-american Biological Control Laboratory
item BRUCE, TIMOTHY - Auburn University

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2023
Publication Date: 1/12/2024
Citation: Wise, A.L., Lafrentz, B.R., Kelly, A.M., Liles, M.R., Griffin, M.J., Beck, B.H., Bruce, T.J. 2024. Coinfection of channel catfish (Ictalurus punctatus) with virulent Aeromonas hydrophila and Flavobacterium covae exacerbates mortality. Journal of Fish Diseases. https://doi.org/10.1111/jfd.13912.
DOI: https://doi.org/10.1111/jfd.13912

Interpretive Summary: This study evaluates the impact of co-infection with Flavobacterium covae and virulent Aeromonas hydrophila in juvenile channel catfish, revealing significantly increased mortality rates when both pathogens are present together. Immune gene expression analysis showed heightened inflammatory responses, highlighting the severity of co-infection. These findings contribute to catfish health research by improving the understanding of bacterial co-infections, aiding in the development of targeted prevention and treatment strategies for disease management in aquaculture.

Technical Abstract: Flavobacterium covae and virulent Aeromonas hydrophila are prevalent bacterial patho-gens within the US catfish industry that can cause high mortality in production ponds. An assessment of in vivo bacterial coinfection with virulent A. hydrophila (ML09-119)and F. covae (ALG- 00-530) was conducted in juvenile channel catfish (Ictalurus punctatus). Catfish were divided into seven treatments: (1) mock control; (2) and (3) high and low doses of virulent A. hydrophila; (4) and (5) high and low doses of F. covae; (6)and (7) simultaneous challenge with high and low doses of virulent A. hydrophila and F. covae. In addition to the mortality assessment, anterior kidney and spleen were collected to evaluate immune gene expression, as well as quantify bacterial load by qPCR. At 96 h post-challenge (hpc), the high dose of virulent A. hydrophila infection (immersed in 2.3 × 10e7 CFU mL-1 ) resulted in cumulative percent mortality (CPM) of 28.3 ± 9.5%, while the high dose of F. covae (immersed in 5.2 × 10e6 CFU mL-1 ) yielded CPM of 23.3 ± 12.9%. When these pathogens were delivered in combination, CPM significantly increased for both the high- (98.3 ± 1.36%) and low-dose combinations(76.7 ± 17.05%) (p < .001). Lysozyme activity was found to be different at 24 and 48 hpc, with the high-dose vAh group demonstrating greater levels than unexposed control fish at each time point. Three proinflammatory cytokines (tnfa, il8, il1b) demonstrated increased expression levels at 48 hpc. These results demonstrate the additive effects on mortality when these two pathogens are combined. The synthesis of these mortality and health metrics advances our understanding of coinfections of these two important catfish pathogens and will aid fish health diagnosticians and channel catfish producers in developing therapeutants and prevention methods to control bacterial coinfections.