In U.S. channel catfish (Ictalurus punctatus ) production, bacterial pathogens such as Edwardsiella ictaluri, Aeromonas hydrophila, and columnaris-causing bacteria (Flavobacterium spp.) are primarily responsible for disease within production ponds . Further, channel catfish virus (CCV) has also played a role in production mortality and mainly impacts fry and fingerling production. In a pond -rearing environment, catfish are simultaneously exposed to multiple aquatic pathogens , and issues with water quality and stress can influence pathogen and host dynamics . Pathogen coinfections may increase the severity of the constituent pathogens and elevate mortality, thus potentiating economic losses for U.S. producers . A recent study assessed and characterized the effects of bacterial and viral coinfection in juvenile channel catfish . Single infections of F. covae (ALG-00-530) and CCV (2013-CCV-DRB) , alongside a mixed treatment group, were incorporated into the experimental design.
With respect to experimental treatment groups , the single virulent F. covae infection (immersed in a final concentration of 3.05 x 105 CFU mL-1; 30 mL of inoculum in 10L of rearing water ) resulted in a total cumulative percent mortality (CPM) of 21.3 ± 6.7 %. T he CCV group (immersed in 10 L of rearing water with 6 mL of a 1.05 x 108 PFU mL-1 viral stock added ) was 77.0 ± 9.2 %. A coinfection half-dose combination (15 mL of F. covae and 3 mL of CCV in 10 L of rearing water) of each pathogen demonstrated pronounced mortality (100.0 ± 0.0 %) over 13 days folloωing the initial challenge.
Trial results indicate changes in both 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 mixed infection exposures. Reducing disease outbreaks in catfish farming is critical to enhancing production yields and quality products , and comprehending infection dynamics of pathogens coinfections will provide more insight into targeted control measures for catfish health.