The efficacy of inactivated Escherichia coli autogenous vaccines against the E. coli peritonitis syndrome in layers.

Autogenous Escherichia coli vaccines to prevent the E. coli peritonitis syndrome (EPS) in laying hens are often used in the field, although their effectiveness has not been demonstrated yet. Therefore, in this study, which consisted of two experiments, their efficacy was assessed. In the first experiment, the EPS-inducing ability of three E. coli isolates originating from bone marrow of hens that died due to EPS and with different Pulsed-Field Gel Electrophoresis patterns, was examined by intravenous inoculation of the isolates in 17-week-old brown layers. Based on the results one isolate was chosen for the preparation of the vaccines and for homologous challenge and another one for heterologous challenge performed in the second experiment. In the named experiment, groups of laying hens which had been vaccinated intramuscularly at 14 and 18 weeks of age with inactivated vaccine either formulated as aqueous suspension or as water-in-oil emulsion were homologously or heterologously challenged per aerosol at 30 weeks of age. The vaccines contained ≥108.2 formaldehyde-inactivated colony-forming units (cfu) of E. coli per hen dose in 0.5 ml. The estimated E. coli challenge dose uptake ranged from 105.8 to 106.5  cfu per hen. Groups consisted of 18 hens each and were housed in separate isolators from 27 weeks of age. Control groups were included in this experiment, which was ended eight days after challenge. Vaccinations had no effect on body growth and both vaccine types induced (almost) complete protection against homologous challenge, while protection against heterologous challenge was inconclusive.