Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

ASSESSMENT OF COINFECTION WITH Flavobacterium covae AND CHANNEL CATFISH VIRUS IN CHANNEL CATFISH Ictalurus punctatus FINGERLINGS

Timothy J. Bruce*,  Amber  E. Johnsto n, Allison L. Wise,  Courtney E. Harrison,  Brent M. Vuglar , Jason W. Abernathy ,  and Benjamin R. LaFrentz

 

School of Fisheries, Aquaculture, and Aquatic Sciences

203 Swingle Hall

Auburn University

Auburn, AL 36849

tjb0089@auburn.edu

 



 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.