Immune response and histopathological alterations in vital organs of Labeo rohita (Hamilton, 1822) challenged with pathogenic Aeromonas veronii

Abstract

Aeromonas veronii is one of the principal bacterial pathogens of freshwater fishes. The present study has examined immunological and histopathological alterations induced by A. veronii in Labeo rohita one of the most important Indian major carps. The healthy Labeo rohita fingerlings were challenged with pathogenic A. veronii suspension of 104,105, 106, 107 and 108 CFU mL-1. The study demonstrated that the lethal dose (LD50-96h) of A. veronii for L. rohita is 7.5 × 106 CFU mL-1. The infected fish showed abnormal swimming behaviour, erratic swimming, hemorrhages, lethargy and reducing feeding frequency during the initial phase of infection. Within 24 h of infection 86.6% and 100% mortality were recorded the bacterial concentration 108 and 109 CFU mL-1, respectively. Within 24 h of challenge, the respiratory burst, myeloperoxidase activity, bactericidal activity, and lysozyme activity increased significantly (