The effect of ascogen on the immune response of Tilapia fish to Aeromonas hydrophila vaccine

Abstract

The effects of feeding ascogen (5 g kg-1 feed) on the humoral and cell-mediate immune response after immunization of tilapia by intramuscular injection (IM) and direct immersion (DI) with formalin killed Aeromonas hydrophila vaccine (FKAHV) were studied. The results showed that ascogen had a marked immunopotentiating effect after IM as well as after DI vaccination. The immunopotentiating effect of ascogen covered both the humoral and cell-mediated immune response. It was manifested by a marked rise in the geometric mean of antibody titres (haemagglutinating units, HAU) at day 70 after vaccination which reached 409·6 ± 62·71 (after IM) and 48.0 ± 10·.12 (after DI) compared to the vaccinated control groups (57·6 ± 6·40 and 11·2 ± 1·96), respectively. In addition, the mitogenic response of lymphocytes obtained from fish fed with ration containing ascogen was significantly stronger than that of lymphocytes isolated from the control group. Supplementation of ascogen before and after vaccination increased the macrophage migration inhibition percent from 14 to 84 days after vaccination. The relative percent survival of challenged fish after IM and DI vaccination was 89·80% and 40·82% in ascogen supplemented groups compared to the vaccinated nontreated control groups where it was 75·51% and 10·20%, respectively.