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The Epidemiologic Aspects of Salmonella Shedding in Wild Birds of TExas
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Wildlife have become increasingly important as vectors for zoonotic disease. As reservoirs, wild birds have some of the greatest potential to disseminate pathogens across a large area. Due to its broad host range and public health importance, the transmission of Salmonella in birds can carry significant risks to human and animal health. The objectives of this dissertation is to determine the prevalence of Salmonella shedding in birds in various settings, to identify potential risks to human and animal health, and to evaluate ecological factors that may affect Salmonella prevalence. Wild birds were sampled in three settings: passerines in an urban environment in eastern Texas, waterfowl in wildlife management areas along the Texas coast, and passerines at a feedlot in central Texas. Demographic and environmental data was collected for each sampled bird. Standard bacteriologic culture methods were used to isolate Salmonella and, in most cases, isolates were characterized by serotype and antimicrobial susceptibility. Overall, the apparent prevalence of Salmonella shedding was very low compared to domestic species such as cattle and domestic poultry. In urban bird species, 1.8% (2/114) were found to be shedding Salmonella. This suggests that the threat these birds pose to public health is limited. However, the large numbers in which these birds congregate in urban areas, especially near grocery and retail stores, makes even the low prevalence of Salmonella shedding still a concern. Similarly, in waterfowl the prevalence of Salmonella shedding was very low (0.5%, 2/375). While the tendency of waterfowl to utilize agricultural fields and surface waters may potentially lead to contamination, the risk to public health appears minimal compared to the risk posed by Salmonella shedding in domestic poultry. Prevalence of Salmonella shedding was dramatically different in wild birds congregating in feedlots with 29.2% (28/96). This contrast is interesting considering that many of the same species as sampled in an urban setting were also sampled at the feedlot. The prevalence of Salmonella shedding in birds was not significantly associated with the prevalence of Salmonella shedding in cattle. This dissertation shows that prevalence of Salmonella shedding among wild birds in Texas can vary dramatically and suggests that environmental factors may affect the prevalence. More research will need to be done to determine how these factors influence the prevalence in birds and what the prevalence of shedding is in other bird groups in Texas.
Grigar, Mary Katherine (2018). The Epidemiologic Aspects of Salmonella Shedding in Wild Birds of TExas. Doctoral dissertation, Texas A & M University. Available electronically from