Evaluation of haemato-biochemical changes, oxidative stress response and stress related gene expressions in juvenile Labeo rohita (Hamilton, 1822) in response to Mycobacterium fortuitum infection

Abstract

Non-tuberculous mycobacteria present in aquaculture systems can infect and influence the physio-chemical blood parameters of captive fish. The aim of this study was to examine the changes in haematological and biochemical parameters along with expression of stress related genes in response to Mycobacterium fortuitum infection in the Indian major carp, rohu Labeo rohita (Hamilton, 1822). Juveniles of L. rohita were experimentally infected with M. fortuitum strain ATCC 6841, by immersion challenge at three different dosages of 5x105 cfu fish-1 (group T2 ), 5x106 cfu fish-1 (group T3 ) and 5x107 cfu fish-1 (group T4 ) along with a control group. After 60 days post-infection, fishes in groups T2 , T3 and T4 were observed with necrotic lesions in skin and M. fortuitum was recovered from moribund fishes. Heat shock protein (hsp) gene expression analysis was performed in liver tissues by RT-PCR and hsps were analysed by Western Blotting in fishes of all treatment groups and control. Significant changes (p<0.05) were found in haemato-biochemical parameters including glucose, cortisol, blood parameters, liver enzymes, serum proteins and catalase and superoxidase dismutase activity along with mRNA expression of hsp genes viz, hsp60, hsp70, hsp78, hsp90 and hsp47 within groups T3 and T4 in comparison to control. The results suggest the pathogenicity of M. fortuitum (ATCC 6841) to L. rohita by promoting stress parameters and the transcription level of stress related genes. Keywords: Fish tuberculosis, Heat shock protein, Mycobacterium fortuitum, Mycobacteriosis, Rohu