Physiological and immune response of Litopenaeus vannamei undergoing the acute phase of the necrotizing hepatopancreatitis disease and after being treated with oxytetracycline and FF

Abstract

The physiological and immune responses of adult shrimp (Litopenaeus vannamei) undergoing the acute phase of the necrotizing hepatopancreatitis (NHP) disease and the efficiency of oxytetracycline (OXI) and florfenicol (FF) to eliminate the pathogen were evaluated. Four shrimp groups were considered: three groups infected with necrotizing hepatopancreatitis bacteria (NHP-B) (two treated with antibiotics and a positive control) and one group non-infected (negative control). Hemolymph concentration of glucose, lactate, acylglycerides, cholesterol, total protein, aminotransferases, superoxide dismutase, and the transcriptional expression of several immune related genes were monitored at the acute phase of the disease, and at 15 and 20 days after administration of antibiotics (daa). Shrimp from the positive control registered a mortality of 100%. NHP-B infection affected the immu-nophysiological response of shrimp; herein, most of the parameters were significantly up regulated in infected shrimp before the use of antibiotics, compared to the negative control. Increased transcriptional levels of clotting protein, lipopolysaccharide and β-1-3-glucan binding protein (LGBP), serine protease, peroxinectin, lysozyme, heat shock proteins (HSP) 60 and 70 were detected in shrimp treated with OXI. At 20 daa NHP-B was still detected in FF-treated shrimp, but not in OXI-treated shrimp. It is hypothesized that despite none of the antibiotics per se eliminated the bacterium, both had a negative effect on its virulence. OXI seems to have a greater effect, allowing shrimp to integrate a better immune response at 15 daa.