Efficacy of inactivated whole-cell vaccines against streptococcosis in pigeons

Two experimental vaccines were developed and evaluated for their efficacy against Streptococcus gallolyticus septicaemia in pigeons. Both vaccines contained whole-cell formaldehyde-inactivated S. gallolyticus serotype 1 bacteria and a mineral oil adjuvant. The supernatant of a S. gallolyticus broth culture was also added to one of the vaccines. Four groups of 10 pigeons were inoculated either once, or twice, with a 4-week interval, with one of the vaccines. Four weeks after the last vaccination, pigeons were challenged by intravenous inoculation with S. gallolyticus serotype 1. Morbidity after infection was not significantly different between groups of pigeons vaccinated with the two vaccines. In groups of pigeons vaccinated once, morbidity after infection ranged from 50 to 70%; in pigeons vaccinated twice, morbidity was 10 to 30%. In a non-vaccinated inoculated control group, the morbidity was 80%. It was concluded that double vaccination can result in some clinical protection against streptococcosis in pigeons.