An Investigation of Epidemiological Approaches for Syndromic Surveillance of Cattle Health using Ontario Condemnation Data
This thesis is an investigation of quantitative methods for food animal syndromic surveillance utilizing bovine abattoir condemnation data as a case study to illustrate approaches to using Ontario provincial abattoir data. There has been little investigation into the suitability of bovine abattoir condemnation data in Ontario for its use in a food animal syndromic surveillance system and the quantitative methods necessary for this type of system. Overall, it was found bovine condemnation data from provincially inspected abattoirs to be useful for food animal syndromic surveillance since they provided a more regionally detailed picture of emerging diseases in Ontario than data from federal abattoirs. Disease-related and non-disease factors such as season and sales price were shown to have an impact on condemnation rates, and accounting for relevant predictable factors considerably affects the results of quantitative cluster detection methods. This was demonstrated by comparison of various space-time scan statistics with distinct options to control for covariate information. The results from this study found that model-adjusted approaches for controlling for covariates in scan statistics appeared to perform best in terms of ability to include all important covariates and suitability for use with bovine abattoir condemnation data. Furthermore, the efficiency of syndromic surveillance was investigated by comparing various sentinel abattoir selection approaches to reduce the number of sample sites while still maintaining the overall trends in the full dataset. The most effective sentinel selection approach utilized data from abattoirs in operation all weeks of the year, and this approach shows promise for the integration of sentinel sites into a sentinel syndromic surveillance system. While these findings suggest that bovine abattoir condemnation data would be suitable for integration into a food animal syndromic surveillance system, there are some limitations including data quality issues and current methodological approaches. Future research is recommended to focus on the following before formalizing a food animal syndromic surveillance system in Ontario: (i) developing an improved meat inspector training program; (ii) finding ways to harmonize the condemnation process by standardizing definitions for reasons for condemnation; and (iii) validating methodological findings from this thesis by studying simulated and/or documented historical outbreak data.