Experimental Salmonella dublin infection in calves.

An experimental model of Salmonella dublin infection in calves for the purpose of evaluating antibacterial compounds was developed. Oral administration of the bacterium produced variable results and subsequently the organism was injected intravenously into one-week-old calves. Symptoms observed were consistent with those described in naturally occurring cases. An analysis of the mortality and clinical signs in both control and treated calves showed that the severity of the disease was exacerbated by the presence of specific antibody. It is argued that some symptoms presented were consistent with anaphylactic or Arthus-type hypersensitivity. Anaphylaxis was associated with antibody probably derived from maternal colostrum whereas Arthus hypersensitivity was probably due to antibody synthesised by the calf itself. There was an inverse relationship between low initial antibody titres and the survival period. Tests of antibacterial efficacy may best be done in colostrum deprived animals in which the symptoms will be dissociated from passively acquired antibody.