Study of changes in serum antibody after intra-peritoneal and intra-muscular injection of killed Aeromonas hydrophila on common carp (Cyprinus carpio)

Aeromonas hydrophila is one of the most important pathogenic bacteria in fishes that cause bacterial septicemia. In this study, 120 pieces of common carp (Cyprinus carpio) weighting 30-70g, were divided in to five different groups (two groups of 30 pieces and three groups of 20 pieces in each). Formalin killed Aeromonas hydrophila were injected intramuscularly and intra-peritonealy to two groups (each group 30 fish). As a control, normal saline were injected intra-muscularly and intra-peritonealy to two groups (each group 20 fish) and one group (20 fish) was not received injection. Blood samples were collected from all fishes 2 weeks after injection and titer of anti-Aeromonas antibody determined by tube agglutination test. Antibody titer in intra-muscular injected group was significantly higher than normal saline injected group. Antibody titer in intra-peritoneal injected group was also significantly higher than normal saline injected group (P< 0.05). The result showed that there was a significant difference between titer of killed bacteria received groups in comparison with control groups (P<0.05), but there was not significant difference (P>0.05) between titer of intra-muscular and intra-peritoneal becterin received groups. According to our results, injection of killed bacteria in both methods of injection, significantly elevated the serum antibody level.