Chasing Salmonella Typhimurium in free range egg production system

- Shedding of Salmonella was significantly higher in summer.
- There was no direct association between the Salmonella shedding and corticosterone levels in faeces.
- S. Typhimurium MLVA pattern evolved over the period of sample collection.
- Wild birds and foxes appear to play an important role in S. Typhimurium ecology.

Free range production systems are becoming a major source of egg production in Australia and worldwide. This study investigated shedding and ecology of Salmonella Typhimurium and Salmonella species in a free range layer flock, wild birds and foxes in the vicinity of the free range farm in different seasons. Shedding of Salmonella was significantly higher in summer. Within the shed, overall, Salmonella prevalence was highest in dust. Corticosterone level in faeces was highest in spring and lowest in winter. There was no direct association between the Salmonella shedding (MPN/gm) and corticosterone levels in faeces. Salmonella Typhimurium MLVA types isolated from fox and wild birds were similar to MLVA types isolated from layer flock and reported during human food borne illness. Wild birds and foxes appear to play an important role in S. Typhimurium ecology and food safety. Environmental factors could play a role in evolution of S. Typhimurium in free range environment.