The response of New-season Nile tilapia to Aeromonas hydrophila vaccine.

The present study was conducted to recognize the response of new-season Nile tilapia to Aeromonas hydrophila vaccine. Four hundred new-season Nile tilapia were used in this study and divided into two equal groups, the first group served as control and the 2(nd) group was vaccinated with Aeromonas hydrophila vaccine via intraperitoneal injection. The antibody titer, Hematocrit level (HCV), Nitroblue tetrazolium activity (NBT) and lysozyme activity of new-season Nile tilapia was measured at the end of the 1(st), 2(nd), 3(rd), 4(th), 6(th), 8(th) and 10(th) week post vaccination (PV). Challenge with A. hydrophila was carried out at the end of the 6(th), 8(th) and 10(th) week PV. The antibody titer of vaccinated new-season tilapia showed significant higher values than unvaccinated group at all periods. The hematocrit and lysozymes activity values showed, a non significant increased in comparison with unvaccinated group at all periods PV. The NBT was significantly increased in vaccinated tilapia in comparison with unvaccinated group at all periods except one week PV. The relative level of protection of vaccinated tilapia after challenge infection was highest at 6(th) week PV in the new-season tilapia. We conclude that, vaccination against A. hydrophila increase the resistance of tilapia to such infection and consequently improve the survival and economic outcome. Other more applicable routes of vaccination should be investigated to be used on a large scale.