Assessment of coinfection with Flavobacterium covae and channel catfish virus In channel catfish Ictalurus punctatus fingerlings

Authors: BRUCE, TIMOTHY - Auburn University; Johnston, Amber; Abernathy, Jason; Wise, Allison; HARRISON, COURTNEY - Auburn University; VUGLAR, BRENT - Auburn University; Lafrentz, Benjamin

Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/2024
Publication Date: 3/4/2024
Citation: Bruce, T.J., Johnston, A.E., Abernathy, J.W., Wise, A.L., Harrison, C.E., Vuglar, B.M., Lafrentz, B.R. 2024. Assessment of coinfection with Flavobacterium covae and channel catfish virus In channel catfish Ictalurus punctatus fingerlings. Annual Eastern Fish Health Workshop [absract]. 62.

Interpretive Summary:

Technical Abstract: In the U.S. channel catfish (Ictalurus punctatus) production pond environment, catfish are simultaneously exposed to multiple aquatic pathogens, and issues with water quality and stress can influence pathogen and host dynamics. Bacterial pathogens such as Flavobacterium covae, Aeromonas hydrophila, and Edwardsiella ictaluri are leading causes of disease within the industry. Further, channel catfish virus (CCV) has also played a role in production mortality and can impact fry and fingerling production. Pathogen coinfections may increase the severity of the constituent pathogens and elevate mortality, thus potentiating economic losses for U.S. catfish producers. In this research, the effects of bacterial and viral coinfection in juvenile channel catfish were assessed and characterized. Single infections of F. covae (ALG-00-530) and CCV (2013-CCV-DRB), alongside a coinfection treatment group, were incorporated into the experimental design. The single F. covae infection (immersed in a final concentration of 3.05 x 10^5 CFU/mL; 30 mL of inoculum in 10 L of rearing water), resulted in cumulative percent mortality (CPM) of 21.3 +/- 6.7%. The single CCV infection (immersed with 6 mL of 1.05 x 10^8 PFU/mL viral stock in 10 L of rearing water), reached 77.0 +/- 9.2% CPM. For the coinfection, half-doses of each pathogen (15 mL of F. covae and 3 mL of CCV in 10 L of rearing water) were administered together and resulted in pronounced mortality (100%) over 13 days following challenge. Trial results indicate changes in channel catfish mortality levels and trends from simultaneous exposure to multiple pathogens. A further understanding of the channel catfish immune response via transcriptomic analyses may also elucidate host factors involved in coinfection exposures. Reducing disease outbreaks in catfish farming is critical to enhancing production yields and quality products, and an increased understanding of coinfection dynamics will provide more insight into targeted control measures for catfish health.