Coinfection dynamics of experimentally challenged channel catfish (Ictalurus punctatus)

Abstract

Catfish farming is the largest sector of the U.S. aquaculture industry and is of paramount economic importance for Southern U.S. agriculture. Maintaining and improving catfish health is a primary concern for producers, and bacterial pathogens can cause large-scale losses in production ponds. Edwardsiella ictaluri, Aeromonas hydrophila, and Flavobacterium columnare are the most predominant bacterial pathogens causing mortality within catfish production facilities. Interestingly, disease outbreaks resulting in high mortalities may also be coupled with multiple pathogens. Bacterial coinfections may often go unreported or misdiagnosed, resulting in a lack of proper mitigation for the coinfective effectors. Bacterial coinfections may increase the severity of the constituent pathogens along with grossly increasing mortality, thus creating economic losses. To assess and characterize the effects of bacterial coinfections, two pathogen challenge trials were conducted to compare in vivo virulence and fish immune responses resulting from exposure to single and coinfective bacteria. Trial results emphasize the importance of evaluating co-infections and demonstrate dramatic increases in mortality when two pathogens are combined, even at half-doses. The synthesis of these mortality and health metrics will aid fish health diagnosticians and channel catfish producers in developing therapeutants and prevention methods to control bacterial co-infections better.