Molecular fingerprinting evidence of the contribution of wildlife vectors in the maintenance of Salmonella Enteritidis infection in layer farms

AIMS: To provide molecular fingerprinting evidence of the contribution of wildlife vectors in the on-farm epidemiology of Salmonella Enteritidis infections. METHODS AND RESULTS: Salmonella Enteritidis strains were isolated from wildlife and from farm environment samples collected in 10 egg layer farms. Isolates were typed using plasmid profiling, XbaI-pulsed field gel electrophoresis and PstI-SphI ribotyping. In all 10 farms we were able to identify the same S. Enteritidis clones in wildlife vectors and farm environment. On several occasions the same clones were found before and after cleansing and disinfecting the farm premises. Also in some instances the same clones were present in mice samples, egg contents and spent hens. CONCLUSIONS: Definitive molecular evidence for the involvement of several wildlife species (mice, rats, flies, litter beetles and foxes) in the maintenance of S. Enteritidis infection on farms has been presented. Failures in biosecurity seriously compromise the control of this pathogen on laying farms. SIGNIFICANCE AND IMPACT OF THE STUDY: This paper reports on the use of molecular tools for the study of the epidemiology of S. Enteritidis. It gives useful information to be considered in control programmes for this organism on poultry farms.