Escherichia coli infection is a common production disease in poultry production. In egg-laying hens oviduct infections are the primary manifestation. Oviduct infections contribute significantly to both outbreak related colibacillosis and normal mortality in adult layer flocks. In broilers and pullets vaccination with live vaccine (Poulvac® E. coli) can decrease the losses due to colibacillosis. Despite, not marketed nor documented and validated for effect on oviduct infections the vaccine is widely used in Danish layers.
The aim of the present study was to investigate the effect of vaccination against E. coli salpingitis (Poulvac® E. coli, 2 and 14 weeks old) in a salpingitis model. In total six groups of vaccinated and unvaccinated layers were surgically inoculated with either a highly virulent E. coli strain (outbreak simulation, ST95), a moderately virulent E. coli strain (simulation of non-outbreak related salpingitis, ST429), or sterile media. Two days post infection (dpi) the vaccinated group receiving ST95 contracted severe clinical symptoms and were for animal welfare reasons euthanized. In the ST95 unvaccinated group the clinical symptoms were slightly less severe and 60% of the hens were euthanized due to clinical diseases, resulting in a significantly lower mortality rate compared to the vaccinated group. Ten dpi all remaining hens were necropsied and bacteriological investigation were performed. No significant difference in the lesions was observed between vaccinated and unvaccinated birds. However, significant strain dependent differences were observed in lesions resulting in severe lesions in the vaccinated birds infected with ST95. Similar strain differences were observed regarding bacteriological re-isolation.
In conclusion, vaccination with live attenuated E. coli does not protect against salpingitis in egg-laying hens under experimental conditions with both regards to outbreak associated E. coli salpingitis and non-outbreak related salpingitis. However long-term unspecific vaccination effects on causes of normal mortality and production parameters remain to be addressed.