| Summary: | Little is known about the epidemiology of infection in wild birds. However, such infections can be zoonotic, transmitted to domestic livestock or both. Previous studies have resulted in conflicting evidence and views as to the role played by wild birds in the epidemiology of infectious diseases. This study aimed to determine the prevalence of a range of bacterial and viral pathogens in wild birds, over appropriate temporal and spatial scales, in order to begin to understand the (potential) role that birds play in the ecology of infectious diseases; in particular, to determine if wild birds act as sources and/or reservoirs of infection for human beings and/or domestic animals. This was achieved by carrying out a series of cross-sectional studies of wild bird populations in north-west England over a two year period. Samples collected from wild birds were examined for bacterial and viral agents including Campylobacter spp., verocytotoxigenic Escherichia coli, Salmonella spp., influenza A virus, avian paramyxovirus type-I, avian metapneumovirus, coronavirus and West Nile virus. Microorganisms were characterised using an array of microbiological and molecular techniques. Phylogenetic and epidemiological analyses were carried out to investigate host-pathogen ecology and evolution and to determine risk factors for the carriage of these agents by wild birds. Salmonellosis in wild passerines was found to be caused by a narrow range of possibly host-adapted S. Typhimurium strains, which were capable of invading and persisting in avian cells, susceptible to antimicrobials and contained a range of virulence genes, but lacked a gene that has been associated with some epidemic strains of S. Typhimurium in humans and livestock. It is suggested that S. Typhimurium infection in wild passerines is maintained within wild bird populations and it is unlikely that these strains represent a large zoonotic risk.
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