Authors : Todd D. Sink , J. Strange Richard , G. Kattesh Henry and G. Mathew Alan
Abstract: This study examined the effects of stress and pathogen concentration on ESC susceptibility in juvenile catfish. Three stress/disease challenges were conducted at concentrations of 1.4, 0.7 and 0.4 Log colony forming units/L of Edwardsiella ictaluri. Twenty-five fingerling catfish per tank were confined to plastic nets for 30 or 60 min, while unstressed fish remained free swimming. Blood samples were taken for cortisol analysis and the pathogen was administered at the conclusion of the stress period. Mortalities were monitored for 21 d. Cortisol concentrations differed (p<0.05) among stressor treatments in the high challenge. Additionally, increases in mortality occurred in conjunction with increases in cortisol (unstressed: 22.5�4.2, 30 min: 47.5�5.2, 60 min: 81.7�6.8%). The medium concentration challenge exhibited similar results for cortisol concentrations. Mortality rates were similar to the high dose challenge (unstressed: 7.5�4.2, 30 min: 60.8�13.9, 60 min: 94.2�5.8%). While cortisol concentrations were similar for the low dose challenge, mortality rates were lower (unstressed: 4.2�3.8, 30 min: 18.3�8.2, 60 min: 27.5�5.2%) but still significantly different from each other. This study demonstrates (1) both confinement stress and bacterial pathogen concentration affect disease susceptibility of channel catfish and (2) stress and the concurrent physiologically high concentrations of cortisol are more highly correlated with disease susceptibility than bacterial pathogen load.
Todd D. Sink , J. Strange Richard , G. Kattesh Henry and G. Mathew Alan , 2006. Linking Stress to Increased Mortality of Channel Catfish at Varying Concentrations of Edwardsiella ictaluri. Journal of Animal and Veterinary Advances, 5: 208-214.