Immune responses in different fullsib families of Indian major carp, Labeo rohita, exhibiting differential resistance to Aeromonas hydrophila infection

Abstract

Selection of fish disease resistance may be performed directly via survival and challenge data or indirectly via the identification of the underlying resistance markers responsible for the differential survival. In a preliminary study, the potential correlation of a variety of specific and nonspecific immune parameters with aeromoniasis resistance was investigated in 13 different fullsib families of rohu ( Labeo rohita), one of the important Indian major carp species known to exhibit differential susceptibilities to aeromoniasis in laboratory conditions. The experimental infection of fish through the intraperitoneal route to Aeromonas hydrophila produced mortality ranging from 0 to 100%. The specific immune response as measured through haemagglutination (HA) titre against sheep red blood cells (SRBC) and nonspecific immunity levels (lysozyme activity and natural haemolysin titre) were not found to be significantly different between resistant and susceptible groups. Serum bactericidal activity was found to be higher in groups of rohu resistant to A. hydrophila infection. Nevertheless, significant ( P<0.05) positive correlation between serum bactericidal activity and aeromoniasis was observed. Based on the observations, bactericidal activity appears to play a role in resistance against A. hydrophila infection.