Epidemiology of Salmonella typhimurium infection in calves: persistence of salmonellae on calf units.

Salmonella typhimurium DT204C infection is the commonest cause of salmonellosis in calves. On five calf rearing farms a distinct strain, as indicated by plasmid profile analysis, was found to have persisted on the premises for periods ranging from four months to two years, the average being 14 months. The persistence of salmonellae in the environment appears to be an important factor in the epidemiology of calf salmonellosis and clearly indicates the inadequacy of many cleaning and disinfection routines.