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

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

Exploiting scanning surveillance data to inform future strategies for the control of endemic diseases: the example of sheep scab

Scanning surveillance facilitates the monitoring of many endemic diseases of livestock in Great Britain, including sheep scab, an ectoparasitic disease of major welfare and economic burden. There is, however, a drive to improve the cost-effectiveness of animal health surveillance, for example by thoroughly exploiting existing data sources. By analysing the Veterinary Investigation Diagnosis Analysis (VIDA) database, this study aimed to enhance the use of existing scanning surveillance data for sheep scab to identify current trends, highlighting geographical “hotspots” for targeted disease control measures, and identifying a denominator to aid the interpretation of the diagnostic count data. Furthermore, this study collated and assessed the impact of past targeted disease control initiatives using a temporal aberration detection algorithm, the Farrington algorithm, to provide an evidence base towards developing cost-effective disease control strategies. A total of 2,401 positive skin scrapes were recorded from 2003 to 2018. A statistically significant decline in the number of positive skin scrapes diagnosed (p < 0.001) occurred across the study period, and significant clustering was observed in Wales, with a maximum of 47 positive scrapes in Ceredigion in 2007. Scheduled ectoparasite tests was also identified as a potential denominator for the interpretation of positive scrapes by stakeholders. Across the study period, 11 national disease control initiatives occurred: four in Wales, three in England, and four in Scotland. The majority (n = 8) offered free diagnostic testing while the remainder involved knowledge transfer either combined with free testing or skills training and the introduction of the Sheep Scab (Scotland) Order 2010. The Farrington algorithm raised 20 alarms of which 11 occurred within a period of free testing in Wales and one following the introduction of the Sheep Scab (Scotland) Order 2010. In summary, our analysis of the VIDA database has greatly enhanced our knowledge of sheep scab in Great Britain, firstly by identifying areas for targeted action and secondly by offering a framework to measure the impact of future disease control initiatives. Importantly this framework could be applied to inform future strategies for the control of other endemic diseases

Exploiting Scanning Surveillance Data to Assess the Impact of Different Initiatives and Inform Future Strategies to Control Sheep Scab

Veterinary surveillance is an essential tool designed to aid decision making and a fundamental concept in food security, public health and international trade (Hoinville et al., 2013). This study aimed to investigate the use of existing scanning surveillance data for sheep scab to assess the impact of different initiatives and inform future control strategies. The data analysed were submissions with a positive sheep scab diagnosis confirmed through identification of Psoroptes ovis mites in skin scraping in Great Britain for 2003-2018. Information were also collected on all known knowledge transfer, skills training, free testing and legislative actions (initiatives) designed to improve surveillance or decrease disease within the study period for sheep scab. First, a spatial analysis to highlight areas of concern was carried out, followed by an analysis of the effect of past initiatives on temporal patterns (Tongue et al., 2019). A total of 2,401 positive skin scrapes were recorded within the study period. The yearly distribution showed a significant downward trend in positive cases, from a peak of 277 in 2004, to 55 cases in 2015. In the study period nine initiatives occurred. Three of these initiatives had a significant effect on the number of positive cases diagnosed and this type of scheme did evoke the intended response. In conclusion, the analysis of an existing scanning surveillance source enhanced our knowledge of sheep scab by identification of areas for targeted control and offered a framework to measure the impact of future initiatives

Investigating the perceived versus actual gastrointestinal nematode challenge on extensive sheep farms

Extensive farming systems form an integral part of sheep production systems across Europe. However, with innate production handicaps, declining sheep numbers and narrow economic margins, production is becoming increasingly challenging threatening the future sustainability of the industry. Gastrointestinal nematodes (GINs) are a significant cause of production losses to the global sheep industry, with well-established resistance to the major anthelmintic groups. Traditionally, extensive farming systems are not thought to have a significant parasite challenge compared with intensive farms, but there is a need to identify the scale and importance of GINs on extensive farms to inform the need for sustainable control strategies. In this study, a questionnaire of extensive farmers (n=34) was conducted and parasitological data were collected from nine study farms to investigate the perceived versus actual GIN and anthelmintic resistance challenge faced by extensive farms. The results showed a production-limiting challenge on most farms, with a higher GIN challenge observed on improved pastures. Furthermore, over half of the extensive farmers perceived anthelmintic resistance to be a greater problem for intensive farmers, with only 20% of respondents reporting known anthelmintic resistance. However, all study farms had evidence of resistance to at least one group of anthelmintics. Consequently, this study has demonstrated that despite the traditional perception of parasitism on extensive farms, there is a need to increasingly consider its impact and take a proactive approach to sustainable control, with solutions tailored to their unique management

A study into the identity, patterns of infection and potential pathological effects of rumen fluke and the prevalence of co-infections with liver fluke in cattle and sheep

Rumen fluke (RF) are trematode parasites that have increased in prevalence within European ruminant livestock since the 1990s. Morbidity and mortality can result from the development of juvenile flukes in the duodenum, however, evidence for significant impacts of adult fluke in the rumen of the final host is equivocal. The presence of rumen fluke in Scotland had not previously been quantified, so the purpose of this study was to use historical coprological data collected between 2008 and 2018 at the School of Veterinary Medicine in Glasgow to evaluate the frequency of rumen fluke infection and to compare this with the presence of liver fluke. This analysis showed evidence of adult rumen fluke in 6.6% of samples submitted, with a substantial and significant increase in positive diagnoses from 2016, following which positive rumen fluke diagnoses equaled or slightly outnumbered those of liver fluke. A prospective post-mortem examination study was also carried out to determine the presence of rumen and liver fluke in cattle and sheep, to quantify adult rumen fluke burdens and to assess any pathological changes in the reticulorumen and proximal duodenum associated with infection. The presence of rumen fluke in post-mortem cases was 26.9% (n = 18/67), the majority (66.7%, n = 12/18) with burdens of less than 100 adult rumen flukes. There was no significant difference in mean ruminal papillar density and length in animals with and without adult rumen fluke and no significant gross pathology was observed in the rumen or reticulum. Examination of animals with adult rumen fluke provided no evidence of any consistent associations with acute or chronic inflammatory changes in the duodenum. All rumen fluke collected at necropsy were identified by PCR and sequencing as Calicophoron daubneyi

A Study into the Identity, Patterns of Infection and Potential Pathological Effects of Rumen Fluke and the Frequency of Co-Infections with Liver Fluke in Cattle and Sheep

Rumen fluke (RF) are trematode parasites that have increased in prevalence within European ruminant livestock since the 1990s. Morbidity and mortality can result from the development of juvenile flukes in the duodenum, however, evidence for significant impacts of adult fluke in the rumen of the final host is equivocal. The presence of rumen fluke in Scotland had not previously been quantified, so the purpose of this study was to use historical coprological data collected between 2008 and 2018 at the School of Veterinary Medicine in Glasgow to evaluate the frequency of rumen fluke infection and to compare this with the presence of liver fluke. This analysis showed evidence of adult rumen fluke in 6.6% of samples submitted, with a substantial and significant increase in positive diagnoses from 2016, following which positive rumen fluke diagnoses equaled or slightly outnumbered those of liver fluke. A prospective post-mortem examination study was also carried out to determine the presence of rumen and liver fluke in cattle and sheep, to quantify adult rumen fluke burdens and to assess any pathological changes in the reticulorumen and proximal duodenum associated with infection. The presence of rumen fluke in post-mortem cases was 26.9% (n = 18/67), the majority (66.7%, n = 12/18) with burdens of less than 100 adult rumen flukes. There was no significant difference in mean ruminal papillar density and length in animals with and without adult rumen fluke and no significant gross pathology was observed in the rumen or reticulum. Examination of animals with adult rumen fluke provided no evidence of any consistent associations with acute or chronic inflammatory changes in the duodenum. All rumen fluke collected at necropsy were identified by PCR and sequencing as Calicophoron daubneyi.</jats:p

The Identity, Prevalence and Associated Pathology of Adult Rumen Fluke in South West Scotland

No abstract available

Exploiting Scanning Surveillance Data to Assess the Impact of Disease Control Initiatives and Inform Future Strategies to Control Endemic Diseases. The Example of Sheep Scab

Scanning surveillance allows us to monitor the occurrence of many endemic diseases in Great Britain (GB), including sheep scab, an ectoparasitic disease of major economic and welfare burden. The Veterinary Investigation Diagnosis Analysis (VIDA) database records diagnoses made by disease surveillance centres in GB and contributes to the scanning surveillance of sheep scab. This study aimed to investigate the use of the VIDA database to assess the impact of disease control initiatives to inform control strategies using a temporal alarm detection algorithm (TADA). A total of 2,401 positive skin scrapes were recorded from 2003-2018. Significant clustering was observed in Wales, with a maximum of 47 positive scrapes in Ceredigion in 2007. Across the study period 11 national disease control initiatives, organised by stakeholders, industry and government occurred: 4 in Wales, 3 in England and 4 in Scotland. The majority (8) offered free diagnostic testing, and the remaining offered knowledge transfer and free testing, skills training and knowledge transfer, and the introduction of the Sheep Scab (Scotland) Order. The TADA raised 20 alarms, of which 11 occurred within a period of free testing in Wales, and 1 at the introduction of the sheep scab order. In summary, this study shows that further use of the VIDA database enhances our knowledge of sheep scab by identifying areas for targeted action and offers a framework to measure the impact of future disease control initiatives. Additionally, this framework could be applied to inform cost-effective and sustainable strategies for the control of other endemic diseases