Caseload of a farm animal veterinary teaching hospital as a form of passive surveillance with particular reference to bovine viral diarrhoea virus.

Bruguera Sala, Anna (2017) Caseload of a farm animal veterinary teaching hospital as a form of passive surveillance with particular reference to bovine viral diarrhoea virus. MVM(R) thesis, University of Glasgow.

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The provision of animal health surveillance in Scotland has recently been reviewed, identifying the need to optimise surveillance delivery by making use of existing animal health data sources and more cost-efficient approaches. The Scottish Centre for Production Animal Health and Food Safety (SCPAHFS) receives uneconomic farm animal cases referred by first opinion veterinary practitioners who confirm the fitness of each animal for transport. Animals are used for teaching and receive full diagnostic work-ups, including gross post-mortem examinations; they are a potentially important source of animal health data that is already being used for teaching and research, though not yet for surveillance purposes.

With the aim to evaluate the usefulness of the SCPAHFS caseload as a source of surveillance data four studies are presented. The first study analyses and presents the demographics and referral reasons of the animals admitted to the SCPAHFS between January 2006 and December 2015. The second study focuses on the 2015 caseload and compares the diagnoses reached at the SCPAHFS with the 2014 Veterinary Investigation Diagnosis Analysis (VIDA) report. The third study collates additional information from the case files of 51 BVD persistently infected (PI) animals, with the aim to evaluate any changes in their clinical presentation that may have occurred as a consequence of the launch of the Scottish BVD eradication scheme. Finally, the fourth study presents a case study of a BVD outbreak and analyses the impact that the eradication scheme had on this particular farm.

Results of the first study show that the SCPAHFS caseload originated from Central and South-West Scotland and Northern England and is mainly represented by cattle (64%) and sheep (31%), with 5% of pigs, goats and alpacas. These proportions differ from the Scottish livestock population and the samples submitted to VIDA. The main reasons for referral of cases included digestive (31%), systemic (19%) and respiratory diseases (15%) and a proportion of cases were referred without clinical problems (8%). The second study found a clear difference between the diagnoses reached at the SCPAHFS and those included in the VIDA report. Digestive and respiratory diseases were the most common diagnoses at the SCPAHFS, both in cattle and sheep; whereas ‘diagnosis not reached’ and reproductive disease were the main categories in VIDA, followed by digestive conditions in third place. Results of the third study showed that more farmers mentioned BVD in the history of cases admitted after the start of the scheme. Animals PI with BVD virus (BVDV) admitted after the start of the scheme tended to be younger and presented with less clinical disease. In those that presented clinical signs, respiratory disease was the most common finding. In addition, no cases of mucosal disease (MD) have been diagnosed at the SCPAHFS since 2010.

Any source of passive surveillance is exposed to a degree of bias. At the SCPAHFS cases are biased towards chronic, uneconomic conditions. However, results of the presented studies indicate that the SCPAHFS caseload represents a portion of the cattle and sheep population that are not captured by the VIDA system. This could potentially act as a complimentary source of surveillance data. Additionally, the SCPAHFS caseload could also contribute with information on endemic conditions. Results of the third and fourth study confirm the success of the Scottish BVD eradication scheme, as BVD PI cattle appear to be identified and removed at earlier ages, before clinical disease, reducing their contribution to transmission of disease and the chances to develop clinical disease.

Item Type: Thesis (MVM(R))
Qualification Level: Masters
Keywords: surveillance, Scotland, bovine viral diarrhoea, farm animal.
Subjects: S Agriculture > SF Animal culture > SF600 Veterinary Medicine
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine > Pathology Public Health & Disease Investigation
Supervisor's Name: Mellor, Mr. Dominic J., Murdoch, Mr. Fraser R. and Orr, Ms. Jayne
Date of Award: 2017
Depositing User: Ms Anna Bruguera Sala
Unique ID: glathesis:2017-8000
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 07 Mar 2017 08:41
Last Modified: 12 Apr 2017 10:34

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