Experimental Salmonella infection in calves. 2. Virulence and the spread of infection.

Calves with a serum ;H' titre of 1/160 developed a chronic form of salmonellosis after infection with S. dublin. Their growth rate was severely retarded by this illness. An aerogenic strain of S. dublin was found to be much more virulent than an anaerogenic strain. Faecal samples were superior to mouth swabs in detecting animals carrying S. dublin.During transport two uninoculated calves became infected and after transport stress, latent carriers of S. dublin with faecal samples negative for Salmonella for 5 weeks, restarted excretion. At slaughter Salmonella were isolated from viscera and organs and from the surface of five of six carcasses.