Investigation of the efficacy of a genetically-stabile live Salmonella Typhimurium vaccine for use in swine

Hybrid swine (Landrace X Pietrain) aged 3-4 weeks were immunized twice at a n interval of 3 weeks solely by the oral route and by the oral/parenteral r oute to evaluate the efficacy of a live S. Typhimurium vaccine. In each exp eriment a control group was run without vaccination. The animals were chall enged at the age of 8-10 weeks by oral test infection with a labelled S. Ty phimurium DT 104 strain. An ELISA was used to establish the presence of ant ibodies to S. Typhimurium in serum samples, coupled with clinical investiga tion. The presence of the challenge strain in the ileal and caecal mucosa a nd in the ileocolic lymph nodes was investigated quantitatively using the K och plating method to determine the degree of colonization of those organs at the time of slaughter. The clinical course of disease was used to assess the success of vaccination. However, it was not possible to trigger, in a reproducible manner, clinical signs of disease in unvaccinated animals thro ugh infection. The vaccinated animals had a significantly lower (p < 0.05) colonization of the ileal and caecal mucosa than the unvaccinated animals. This was also seen to a lesser degree for the ileocolic lymph nodes.