Persistence of Salmonella Enteritidis Phage Type 4 in the environment and arthropod vectors on an empty free-range chicken farm

The persistence of S. Enteritidis PT4 was studied on a free-range breeding chicken farm which had been depopulated following identification of the organism in breeding birds. The site was sampled periodically for 26 months after depopulation and the organism was found to persist in litter, dried faeces and feed, but not in dust within empty poultry houses, for the whole of that period. Salmonella Enteritidis PT4 was also found in soil samples after 8 months but not 13 months and in faeces from wild mice, foxes and cats but not wild birds or badgers. The organism was also found in adult and larval forms of ground beetles and centipedes. Addition of pullets to a contaminated pen or inclusion of contaminated litter, feed or beetles/larvae to feed did not result in acquisition of infection by birds.