Effects of Stress on Susceptibility of Naive Channel Catfish in Immersion Challenge with<i>Edwardsiella ictaluri</i>

Abstract

The effects of stress on the susceptibility of fingerlings of channel catfish Ictalurus punctatus to Edwardsiella ictaluri during immersion challenges were evaluated. Channel catfish fingerlings were exposed to a standardized confinement stressor for 30 min. Infections were established in stressed and nonstressed channel catfish fingerlings by exposure to E. ictaluri under aerated static conditions for 24 or 48 h. Stress and increased time of static bacterial exposure significantly decreased the survival of channel catfish fingerlings after immersion challenge. This study established a relationship between a behavioral stressor (confinement) and increased susceptibility of channel catfish to E. ictaluri infection. From estimates ofexperimental error, a relationship between the precision of the challenge system and the number of replicate aquaria per treatment was established. This analysis indicated that the immersion challenge is associated with a high degree of variability, which limits the effectiveness of the challenge system to detecting only large differences in treatment effects.