Evaluation of Different Vaccination Strategies for Control of (mas) in Nile Tilapia (o. Niloticus) in Egypt

A highly pathogenic isolate of Aeromonas hydrophila, isolate No1, was identified through evaluation of the Crude extra-cellular product and estimation of LD50. Three types of formalized whole culture Aeromonas hydrophila vaccine (FWC) were prepared, FWC vaccine alone, FWC vaccine mixed with Freund's complete adjuvant (FCA), and FWC vaccine mixed with Freund's incomplete adjuvant (FIA), tested for sterility and administered to female Nile tilapia (Oreochromis niloticus) using two methods of delivery. Microagglutination and the double immuno-diffusion tests were performed on serum, mucus and eggs to evaluate maternal immunity. The relative level of protection (RLP) was calculated after challenge infection. Vaccine safety showed that fish vaccinated with FWC vaccine +FCA expressed severe skin lesions and died. RLP of formalininactivated whole culture vaccine alone (S/C or I /M) or incorporated with FIA (I/M) protected 100, 88.8 and 91.1 percent of vaccinated fish, respectively. Subcutaneous administration of the vaccine incorporated with the adjuvants provided partial protection, 66.6%. Serum and mucus showed increased agglutinins four and six weeks post initial vaccination and up to the 8 week in FWC vaccinated fish and fish subcutaneously vaccinated with FWC+FIA. The agglutinating antibodies from eggs of vaccinated females had an agglutinating titer of 160 compared to 10 in the control. Double immuno-diffusion revealed that antibodies were traced three and four weeks post initial vaccination with WFC vaccine alone and on the 5th week after vaccination with FWC vaccine +FIA. Antibodies were detected on the 4th week in mucus after subcutaneous vaccination. Total protein in mucus increased in the vaccinated fish. Total protein was 3 and 2.1 g/dL in eggs of vaccinated fish and the control, respectively. We concluded that the prepared monovalent formalized whole culture vaccine alone or incorporated with FIA adequately protected tilapia against the homologous virulent isolate. Presence of antibodies in egg samples increased the possibility of maternal transfer of immunity. EVALUATION OF DIFFERENT VACCINATION STRATEGIES FOR CONTROL OF (MAS) IN NILE TILAPIA (O. NILOTICUS) IN EGYPT 1158