COMPARATIVE STUDY ON COMMERCIAL VACCINES AGAINST E.COLI IN BROILER CHICKENS

E. coli infections in avian species have become an economic threat to the poultry industry worldwide. The objective of this study is to determine whether the immunization using commercially available living Escherichia coli vaccines as Nisseiken Avian Colibacillosis Vaccine (Nisseiken Co., Ltd., Ome, Tokyo, Japan) and O78 aroA deleted vaccine (Poulvac ® E.coli, Zoetis) are protective against APEC challenges or not. Ninety eight chicks (Arbor, Acres) of both sexes were divided into seven groups (14 birds/each); two groups were vaccinated at day 1 of age by spray route using Nisseiken Avian colibacillosis Vaccine, then one of them challenged intratracheally with homologous E.coli O78 and the other with heterologus O1 at day 14, the other two groups were vaccinated at day 1 of age by eye drop route using Poulvac ® E.coli, Zoetis vaccine then one of them challenged intratracheally with homologus E.coli O78 and the other with heterologus O1 at day 14. The other two groups were positive control (challenged, unvaccinated); one challenged with O78 and the other with O1 at day 14 using intratracheal route. The last group served as environmental control (non vaccinated, non challenged). At day 28, birds were necropised and examined to evaluate the efficacy of both of the two different vaccines. The best obtained results were recorded to the vaccinated challenged groups with the homologous and heterologous strains and vaccinated by spraying and eye drop methods which showed a decrease in organ lesion scores in comparison to the other groups (non-vaccinated, challenged broilers). These results suggest that the two different vaccines used in our study are efficient in reducing lesion scores against homologous and heterologous challenge using spray and eye drop methods that could lead to minimizing the time for treatment and cases of condemnation in processing plants.