Background and Aim: Avian influenza (AI), which is one of the major respiratory diseases of poultry, and Escherichia coli (E. coli) have caused major economic losses around the world, including in Egypt. Therefore, in this study, we aimed to produce a vaccine from E. coli O157 and AI H5N1 formulated with Montanide ISA70 for the protection of poultry against both diseases.

Materials and Methods: We divided one hundred 3-week-old chicks into four groups: Group 1 was vaccinated with prepared inactivated AI H5N1formulated with Montanide ISA70, Group 2 was vaccinated with inactivated E. coli formulated with Montanide ISA70, Group 3 was vaccinated with combined E. coli and AI H5N1 formulated with Montanide ISA70, and Group 4 was an unvaccinated control group. We measured the immune response using the HI (hemagglutination inhibition) test, enzyme-linked immunosorbent assay (ELISA), and the challenge test.

Results: We found the three vaccines to be safe and sterile during all periods of examination and observation. The HI test showed that Group 1 exhibited specific antibody titers of 2.3 log₂, 4.3 log₂, 7.5 log₂, 7.8 log₂, 8 log₂, and 8.1 log₂ from week 2 to week 7, respectively, post-vaccination. Group 3 exhibited antibody titers of 3.3 log₂, 5.8 log₂, 7.8 log₂, 8 log₂, 8.3 log₂, and 8.3 log₂ from week 2 to week 7, respectively, post-vaccination. The immune response in both groups reached a high titer at week 6. The combined inactivated E. coli and AI H5N1 vaccine generated a higher immune response than the inactivated AI H5N1 vaccine, and a significant difference exists between the two groups. For Groups 2 and 3, the ELISA antibody titer exhibited its lowest value, 1996.5 and 2036.7, respectively, at week 1 post-vaccination; whereas, both groups exhibited the highest titers, 2227.7 (for Group 2) and 2287.3 (for Group 3), in week 3 post-booster. The ELISA for the combined inactivated E. coli and AI H5N1 vaccine had a higher titer than did the inactivated E. coli vaccine, and a significant difference exists between the two groups. Moreover, the protection rate was higher in Group 3, with 100% for E. coli and 90% for the AI H5N1 vaccine.

Conclusion: Our findings demonstrate that producing a combined vaccine using E. coli and AI H5N1 formulated with Montanide ISA70 is recommended for protection against both diseases.

Keywords: avian influenza (H5N1), Escherichia coli O157, enzyme-linked immunosorbent assay, hemagglutination inhibition test, Montanide ISA70.