This study proposes to evaluate the effect of glucocorticoid dexamethasone on the chronic inflammatory response of tilapia (Oerochromis niloticus), vaccinated and challenged with Aeromonas hydrophila. This will be used 96 young tilapia, weighing about 150g each, packed in 12 tanks, 100 L capacity, supplied with water devoid of chlorine, creating four treatments: T1 = vaccinated and treated with glucocorticoids, T2 = not vaccinated treated with glucocorticoids, T3 = Non-vaccinated and treated with glucocorticoids and T4 = not vaccinated and not treated with glucocorticoids. Will be evaluated eight animals per treatment in three periods, two, four and eight days post-challenge (HPD) with inocula of A. hydrophila. The vaccination with the bacterin of A. hydrophila,inactivated with formalin, will be held 15 days before the bacterial challenge, after anesthetizing the fish in an aqueous solution of benzocaine (1:500). In the same anesthetic protocol will be challenged with 1.0 x 108 CFU of A. hydrophila applied on a round glass coverslip (9 mm diameter) to be implanted in the subcutaneous tissue, as well as the treatments are performed with the glucocorticoid dexamethasone in groups T1 and T2, a dose of 2 mg / kg at a concentration of 0.2% , intramuscularly. Therefore, two, four and eight days HPD, the tilapia will be submitted to deep anesthesia for blood collection and determination of complete blood count, as well as to harvest coverslips to be stained with HE for reading on light microscopy. However, the correlation between the hematology and cellular recruitment on the coverslip will provide important support in understanding and characterization of events occurring in the pathophysiology of chronic inflammatory response of tilapia, when previously sensitized and challenged with A. hydrophila.
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