Histopathological study and training centers of melano macrophages during chronic inflammatory reaction of Nile Tilapia, treated with dexamethasone, vaccinated and challenged with Streptococcus agalactiae

Abstract

This study aims to evaluate the histopathological changes and the formation of centers melanomacrophages during chronic inflammatory response of Nile tilapia, Oreochromis niloticus, dexamethasone-treated, vaccinated and challenged with Streptococcus agalactiae. To this end, we used 96 young tilapia, weighing about 150g each, packed in 12 tanks, capacity of 1000 L, supplied with running water devoid of chlorine, forming four treatments: GV = glucocorticoid and vaccinated; glucocorticoid and GN = Not Vaccinated; NV = No glucocorticoids and vaccinated; NN = Not glucocorticoid and unvaccinated. Vaccination and challenge with Streptococcus agalactiae bacterin, inactivated by formalin was done 15 days before and at day zero with 1.0 x 108 CFU inocula applied intramuscularly (Treatments GV and NV) and on a round glass coverslips (9 mm diameter) to be implanted subcutaneously, respectively. Upon implantation treatments were performed with the glucocorticoid dexamethasone and GV groups NG dose of 2mg/kg at a concentration of 0.2%, intramuscularly. Two, four and eight DPI, harvests were made of fragments of the kidney, spleen and liver for histopathological study and training centers melano macrophages. As well as fragments of skeletal striated muscles in the implant site of the coverslip were collected for histopathology at the site of inflammation. The correlation of histopathological findings to those observed in studies erythrocyte, leukocyte, biochemical and somatic, conducted in the first phase of this research (FAPESP Process: 2011/08864-9), provide important information for understanding the effect of glucocorticoids in the pathophysiology of chronic inflammatory response tilapia vaccinated and challenged against S. agalactiae. (AU)