evaluation of the efficacy of humoral immunity response of killed oil adjuvant escherichia coli vaccine in layer chicken against avian e. coli serotype o78 infection

Colibacillosis is one of the most important bacterial diseases of chickens and turkeys which caused by avian pathogenic escherichia coli (apec). mortality, low body weight, and high fcr in colibacillosis affected poultry farms and higher carcass condemnation at slaughterhouse caused great economic impacts on the poultry industry. in recent years, production of homologous and heterologous apec vaccines has been evaluated. in this study, mineral oil as an adjuvant for inactivated e. coli used and inoculated via injection route to laying chicken. at 28 days of age, 60 birds were subsequently divided into six experimental groups of 10 chickens per group. chickens in group control did not receive e. coli vaccines; whereas five treatment groups were vaccinated subcutaneously with a formalin inactivated, mineral-oil adjuvant e. coli vaccine containing isolate of e. coli serotype o78; t1, t2, t3, t4, and t5 groups were vaccinated at 28 days of age with 0.2 ml (8 x106, 16 x106, 33 x106, 66 x106, and 133 x106 cfu/ml) per dose of e. coli o78 respectively. igg antibody titers against e. coli was evaluated 10 weeks after inoculation with elisa method. results showed the significant titer in igg antibodies in the immunized birds compared to the unimmunized control group (p <0.05), anti igg antibodies increased weekly after injection of produced compounds in most vaccinated groups up to week four. overall, prepared e. coli vaccine in razi institute, shiraz branch induced high levels of immune responses in the vaccinated laying hens as revealed by elisa. although, to considerable immunological stimulus it is suggested that all the chickens in the experimental group receive a booster dose four weeks after the first immunization.