Effects of Aeromonas sobria on physiology and fillet quality of market-sized Channel Catfish Ictalurus punctatus

Abstract

Channel Catfish Ictalurus punctatus fillets are rejected by processing plants because of diffuse red discoloration, but the cause of the red discoloration is currently unknown. Previous studies have shown a correlation between Aeromonas sobria and the occurrence of red fillet, although causation has not been established and little is known of the effects of A. sobria on catfish. Therefore, the present study inoculated Channel Catfish with A. sobria to determine whether inoculation induced red discoloration in fillets. Visual examination of the muscle of fish inoculated with A. sobria showed diffuse red blotches around the inoculation area and muscle histology showed increased presence of leukocytes and red blood cells, edema, and necrosis. Inoculation with A. sobria also resulted in necrosis of hematopoietic tissue, interstitial hemorrhage and melanomacrophage aggregates in the posterior kidney, and inflammation in the anterior kidney and spleen. These findings demonstrate intramuscular inoculation of A. sobria can result in red fillets and impact hematopoietic and erythrocytic tissues. Further research will be necessary to assess red fillet prevention and control for both catfish farmers and processors.