The effect of vaccination on the course of an experimental Salmonella typhimurium infection in racing pigeons

Two killed adjuvanted vaccines were evaluated for their efficacy against salmonellosis in pigeons. Both vaccines contained whole-cell formaldehyde-inactivated Salmonella typhimurium var. Copenhagen bacteria. Two groups of 10 pigeons were inoculated twice with a 3-week interval with one of the vaccines. Ten weeks after the second vaccination, all vaccinated pigeons as well as 10 non-vaccinated birds were challenged by crop inoculation of 10(9) colony-forming units of a Salmonella serotype Typhimurium var. Copenhagen strain. Ten pigeons that were not vaccinated or challenged served as negative controls. As determined by clinical examination, plasma chemistry and necropsy, neither vaccine induced protection against challenge. The only significant effects observed were a reduction in the level of faecal shedding and a less severe polydipsia in the pigeons treated with one of the two vaccines. Results of this study indicate that vaccination against salmonellosis in pigeons with killed vaccines may not be very useful. However, the ability of certain vaccines to reduce shedding may contribute to the control of salmonellosis in infected pigeon lofts.