Immunogenicity evaluation of Aeromonas hydrophila biofilm vaccine on the fingerling Common carp (Cyprinus carpio)

Despite the many advantage of oral vaccines, this kind of vaccines have a low efficiency and little application in aquaculture due to their antigens destruction in digestive system of fish. Chitin is a natural polymer, while Aeromonas bacteria produce a biofilm of it that cause to bacteria resist to gastric acid and intestinal enzyme systems. At first vaccine of Aeromonas hydrophilia biofilmproduced and then its oral and injection administration was evaluated in common carp. Therefore, 700 carp (46 ± 14) grams, 9 equal treatments and three replications as the first to fourth treatment with Biofilm Vaccine, inactivation Bacteria, Chitin + Culture media and Chitin were oral administered safely, the fifth to eighth treatments were immunized with the injection method safely, the ninth treatment without any vaccine was considered as control group. The fish were injected with concentration of LD50 of Aeromonas hydrophilia bacteria (Mc Farland 8= 2.4×109) on the 60th day. The mortality rate was recorded within 10 days and the relative percent survival (RPS) of each treatment was determined. The results showed that the RPS levels highest were related to injection biofilms, oral biofilm and inactivation Bacteria injection, which was significantly higher than of the other treatments (P <0.05).The efficacy of the injection vaccine was not affected by Biofilm (P = 0.098), although the oral vaccine was influenced significantly by Biofilm (P <0.05).