Abstract
Columnaris disease, caused by Flavobacterium columnare, is a serious bacterial disease responsible for causing devastating rates of mortality in numerous species of freshwater fish. This disease can cause mortalities of up to 100% within 24 h, leading to severe economic losses in the aquaculture industry. Notwithstanding the enormous impacts this disease can have, very little is known regarding the interaction between the host and bacterium. To gain a better understanding of the host immune response, an attempt has been made to study the sequential changes in innate immunity parameters of Catla catla, following bath challenge with F. columnare. The clinical signs in challenged fish included lethargy, respiratory distress, swimming near the water surface and accelerated opercular movements. Histopathological examination of the gills from infected fish revealed the presence of bacterial masses in the gills, fusion of secondary filaments and sloughing of epithelial cells with a consequential disruption to the gill architecture within 24–48 h. Importantly, some innate immunity parameters, namely the production of reactive oxygen species and nitric oxide as well as serum myeloperoxidase activity showed significant increases (p < .05) during the initial stages of infection i.e. up to 12 h post infection (hpi). The other measured parameters, such as alternative complement activity (ACH50) and total anti-protease activity were significantly decreased (p < .05) in the experimental group up to 12 and 24 hpi, respectively. Further, significant increases (p < .05) in lysozyme and ACH50 activity were observed from 12 and 48 hpi, respectively. Total serum protein and globulin level declined significantly (p < .05) in the later stages of infection, whereas the α-2 macroglobulin activity and serum albumin level were unchanged throughout the experiment. This study indicates that the immune response in catla is modulated following infection with F. columnare. Knowledge regarding changes in the immune response will help in developing strategies for improving resistance against columnaris disease.
Published Version
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