Immuno-pathological changes in Indian catfish Clarias magur (Hamilton, 1822) upon experimental challenge with Aeromonas hydropila

Motile Aeromonas septicaemia (MAS), caused by Aeromonas hydrophila, is one of the most significant problem among the bacterial diseases responsible for causing mortality in catfishes. The objective this study was to understand the modulation of innate immune parameters and histopathological alteration in Indian catfish Clarias magur (Hamilton, 1822), following intraperitoneal injection with A. hydrophila. At 3 to 8 h post-infection (hpi), respiratory burst activity, myeloperoxidase, protease, total anti-protease and α2 macroglobulin increased significantly (p<0.05) indicating immune response of host against pathogen invasion at an early stage of infection. The total protein, albumin, albumin/globulin ratio and bactericidal activity were significantly decreased indicating the response of pathogen to suppress host immune response to establish infection. Serum bactericidal activity, bacterial agglutination titre and lysozyme activity increased significantly at 24 hpi. Histopathological examination of infected fish revealed the accumulation of melanomacrophage centres, congestion, hepatocyte degeneration and vacuolated hepatocytes of liver; hyaline droplet accumulation, lymphocytes infiltration and diffuse necrosis of renal tubule in kidney; unilateral fusion of secondary gill lamellae, leukocytic infiltration as well as dilated central venous sinus in gills. Knowledge regarding the immune response in magur could be useful for developing strategies for improving disease resistance against A. hydrophila infection. Keywords: Aeromonas hydrophila, Histopathological alterations, Indian catfish, Innate immune parameters, Intraperitoneal challenge