Elimination of Salmonella typhimurium infection by the strategic movement of pigs.

Three field investigations were carried out to assess the feasibility of raising salmonella-free finishers from pigs born in infected herds, by moving the pigs to clean and disinfected facilities before their expected exposure to the bacteria from the environment. Three herds with persistently high levels of subclinical infection with S typhimurium in the finishing pigs were used. They practised all-in all-out management in the nurseries and in the grower units. A total of 844 pigs were moved, either at weaning, from the nursery, or from the grower unit to newly built or rigorously cleaned and disinfected finishing units with no known history of salmonella infection. No detectable infection was observed at slaughter either serologically or bacteriologically by random testing of the pigs which had been moved, whereas a proportion of the pigs raised at the same time in the continuous systems on the farms were found to be infected.