AUGMENTATION OF SPECIFIC AND NON-SPECIFIC PROTECTION IN OREOCHROMIS NILOTICUS TREATED WITH SOME PREBIOTICS AND / OR BACTERIN

Abstract

We experimentally infected Oreochromis niloticus (O.niloticus) fish with Hafnia alvei (H.alvei), the causative agent of fish haemorrhagic septicemia in order to compare the immunological responses to differ-ent treatments with glucan, alginate and / or in combination with H.alvei bacterin. Elevations in the non-specific defence mechanisms were noted after O. niloticus were bathed in glucan, alginate, and bacterin solutions or in solutions containing the glucan or alginate combined with a bacterin. Blood samples were collected in several times showed an elevation in neutrophil activity through the ability of the cells to stick to glass and produce oxidative radicals where detected by the nitroblue tetrazolium (NBT) assay which increased after treatments in all groups within 48 hours. The numbers of circulatory glass-adherent cells from fish given the alginate, glucan and / or bacterin by bath was significantly higher than at the begining of the experiments or the control levels. Elevated phagocytosis, assessed by increased uptake of glutaraldhyde-treated sheep red blood cells, also confirmed these kinetics. It is obvious that fish given alginate and glucan in combination with bacterin, the kinetics of the non-specific and specific immune responses were significantly remarkable. The most promising group of immunostimulant are the alginate and the glucan and they could play an important role as imm-unomodulators in fish farming and in the prevention of diseases in fish cultures. This paper will present data on such effects with reference mainly to prebiotics and how can induce a systemic effect.