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TLets802516
The use of milk for the surveillance of foot-and-mouth disease
[Thesis]
Armson, Bryony Louise
University of Glasgow
2020
Thesis (Ph.D.)
2020
Effective surveillance of foot-and-mouth disease (FMD) is of the utmost importance in order to understand the disease risks and implement effective control strategies. Epidemiological data obtained for FMD is mostly obtained through recognition and reporting of clinical cases by farmers which has several limitations. For example, under-reporting of disease is common, due to deficiencies in veterinary infrastructure, the effort involved for sample collection, or the repercussions of control measures for farmers. Diagnostic sample types, usually vesicular epithelium and fluid, are invasive and labour intensive to obtain, and can only be collected from acutely infected animals. Therefore, animals with sub-clinical FMD infection (particularly those in vaccinated herds) may not be identified but may still contribute to disease transmission. It is likely, therefore, that the true prevalence of FMD is not accurately known in parts of the world where the disease is endemic. Consequently, the requirement exists for a simple approach for FMD surveillance that does not rely on farmer reporting. Milk is a non-invasive sample type routinely collected from dairy farms and has been utilised for the surveillance of a number of other diseases. Despite numerous publications suggesting the potential of milk as a valuable sample type for foot-and-mouth disease (FMD) surveillance, empirical studies have mainly focused on the risk of transmission via milk, or the detection of FMD virus (FMDV) in milk from individual animals. This thesis aimed to expand on previous studies to determine the utility of milk and its limitations for the surveillance of FMD at the individual and herd level, using data collected from experimental and field studies. A highly sensitive and specific high-throughput RNA extraction and real-time rRT-PCR was optimised and utilised for FMDV RNA genome identification throughout the project. Using this method, it was demonstrated that FMDV RNA genome could be detected up to 28 days post infection using milk samples collected from individual cows. Further analysis using serotyping or lineage-specific rRT-PCR assays and VP1 sequencing of milk samples collected from individual cows in northern Tanzania highlighted the use of milk as a suitable alternative to more invasive sample types such as epithelium. Additionally, storage and shipment condition simulations performed demonstrated good stability of FMDV RNA genome within milk samples. Following these experiments, the potential use of pooled milk for herd-level FMD surveillance was investigated. Two proof-of-concept pilot studies were performed comparing the rRT-PCR results of pooled milk samples collected from both a large-scale dairy farm in Saudi Arabia and milk pooling facilities supplied by smallholder dairy farms in Kenya, with farmer reports of clinical disease. Results supported laboratory limit of detection studies, demonstrating that FMDV could be detected from milk pools of up 10,000 litres, even when there were low numbers of clinical cases. Furthermore, both studies suggested the detection of subclinical infection in milk samples, where disease was not reported. Data from pilot studies performed in this thesis therefore support the use of milk as a simple, non-invasive approach for herd-level FMD surveillance. Further field studies are required to determine the full utility of this method before it may be implemented for targeted/risk-based surveillance alongside existing surveillance systems to facilitate improved knowledge of FMD epidemiology, or for use in FMD contingency plans.
QR Microbiology ; QR355 Virology
Armson, Bryony Louise
University of Glasgow
مطالعه متن کتاب p
[Thesis]
276903
a
Y
