Enhancing the use of data for the scanning surveillance of sheep scab as a model for endemic diseases

Geddes, Eilidh (2021) Enhancing the use of data for the scanning surveillance of sheep scab as a model for endemic diseases. MVM(R) thesis, University of Glasgow.

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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
time , 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.

Item Type: Thesis (MVM(R))
Qualification Level: Masters
Keywords: sheep scab, surveillance, scanning surveillance, data analysis, endemic diseases, temporal aberration detection, disease control.
Subjects: S Agriculture > S Agriculture (General)
S Agriculture > SF Animal culture > SF600 Veterinary Medicine
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
Funder's Name: Department for Environment, Food and Rural Affairs (DEFRA)
Supervisor's Name: Busin, Dr. Valentina and Mohr, Dr. Sibylle
Date of Award: 2021
Depositing User: Miss Eilidh Geddes
Unique ID: glathesis:2021-81975
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 09 Mar 2021 16:57
Last Modified: 09 Mar 2021 17:21
Thesis DOI: 10.5525/gla.thesis.81975
URI: http://theses.gla.ac.uk/id/eprint/81975

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