title: Enhancing the use of data for the scanning surveillance of sheep scab as a model for endemic diseases
Creators: name: Geddes, Eilidh
Publisher: name: University of Glasgow
Year: 2021
Subjects: subject: sheep scab, surveillance, scanning surveillance, data analysis, endemic diseases, temporal aberration detection, disease control.

description: Scanning surveillance facilitates the monitoring of many endemic diseases in Great Britain, including sheep scab, an ectoparasitic disease of major economic and welfare burden. With emerging antiparasitic resistance making the development of control strategies particularly timely, this thesis aimed to enhance the use of data for the scanning surveillance of sheep scab, specifically to guide future control strategies. In Chapter 2 an existing source of scanning surveillance, positive skin scrape diagnoses ('positive scrapes') reported in the Veterinary Investigation Diagnosis Analysis (VIDA) database, were analysed to identify "hotspots" of disease for targeted control and evaluate a potential denominator to improve the interpretation of the count of positive scrapes. The details of all past targeted disease control initiatives were also collated and a temporal aberration detection algorithm (TADA) was applied to investigate their impact on positive scrape diagnoses. Then, in Chapter 3, data from a recently commercialised diagnostic test, the sheep scab ELISA, were collected and analysed, to explore its current use and uptake since commercialisation, identify risk factors for infestation and to consider its value as a complementary source of scanning surveillance. The results of this study showed a decline in positive scrapes, however, the positive scrapes as a proportion of submissions had remained stable. A strong seasonal pattern with high counts in winter was also observed. Wales was identified as a particular "hotspot", with the highest count of positive scrapes. Furthermore, two potential denominators 'scheduled scrapes' and 'skin submissions' were identified to provide further interpretation of positive scrapes. Finally, 11 disease control initiatives were identified and collated, and the TADA offered a framework to objectively measure the impact of these, showing 'free testing' initiatives had the most impact on positive scrape diagnoses. The sheep scab ELISA demonstrated a steady uptake since the beginning of testing, an established seasonal pattern and broad spatial uptake across England and Wales, with few submissions originating from Scotland. The recommended 12-sample submissions for monitoring were most frequently submitted; however, the majority of submissions originated from itchy sheep, showing this test is also widely used to diagnose sheep with clinical or subclinical signs. For the first time, double fencing was shown to significantly decrease the likelihood of a positive serostatus submission; however, common grazing was not identified as a risk factor. Ultimately, this project resulted in the creation of a new data source that could enhance the scanning surveillance of sheep scab. Using sheep scab as a model, the methods used here offer a framework to improve the use of existing and new data sources for the scanning surveillance of other endemic diseases.