Field trails with trivalent inactivated vaccine against colibacillosis in poultry.

Escherichia coli septicaemia or colibacillosis is a serious disease which generally occurs in poultry and which is responsible for considerable losses. In Iran the most common serotypes of E.coli associated with colibacillosis in poultry are O1, O2 and O6. Little is known of the virulence factors which play a role in the pathogenesis of the colibacillosis in poultry. Although many different attachments fimbriae or pili have been described in E.coli, F1 and F11 are the most important. Up till now, there exist no vaccines, offering both a good and broad protection against the wide range of pathogenic avian E.coli. Therefore the multivalent vaccine with F1 and F11 fimbriae may provide good protection against colibacillosis in poultry. The main aim of this research project was the field trails with trivalent inactivated vaccine (with F1 and F11 fimbriae) against colibacillosis in poultry. The vaccine including serorypes O1, O2 and O6 with both F1 and F11 fimbriae were provided. All quality control tests including sterility, safety and potency were performed. Two commercial boiler farms in Arak (No=10000) and Hashtgerd (No=30000) were selected for vaccination by the provided vaccine. Chickens were vaccinated once subcutaneously at 12 days of age with dose of approximately 2x109 cells in 0.3 ml. The chickens were analyzed for colibacillosis for 45 days. The mortality of the vaccinated chickens was recorded. The efficacy of the vaccine was evaluated by mortality, challenge and determination of antibody titer by agglutination test. The results indicated that the mortality of the farms in vaccinated chickens was 4.74% and 7.58% in Hashtgerd and Arak farms respectively. The mortality rate in unvaccinated chickens was 13.12% and 18.18% in Hashtgerd and Arak farms respectively. The challenge of vaccinated chickens indicated that there was no any mortality and morbidity in them. The antibody titer in vaccinated chickens in Hashtgerd and Arak farms were 1/244 and 1/165 respectively. Antibody titer was not observed in unvaccinated chickens. The results revealed that this vaccine provided good protection against colibacillosis in poultry. The results suggesting that the trivalent inactivated vaccine (with F1 and F11 fimbriae) may be useful for protection against colibacillosis in poultry. Key words: Escherichia coli, colibacillosis, trivalent inactivated vaccine, F1 and F11 fimbriae.