Research into zoonoses and emerging diseases to protect public health and animal health in Scotland
Project Lead
Challenges
Vector-borne diseases
Over the past decade, the climate has become milder and wetter across Europe, including Scotland and the rest of the UK, increasing zoonotic fluke (trematodes) infections. One of the most important vector-borne diseases (VBD) is Fasciola, commonly known as liver fluke. There are an estimated 2.5 million people infected worldwide. It is considered a re-emerging disease in the UK. There are reports of the first endemic human infections in Britain since the 1940s. Fasciolosis costs the UK agricultural industry £300 million per year. Since 2020, the Scottish government has put forward recommendations to prioritise the development of industry-wide initiatives for the control of liver fluke, improving animal health and inadvertently reducing the risk of infection to people.
Similarly, zoonotic avian blood flukes causing cercarial dermatitis (CD) is a re-emerging and notifiable disease across Europe. CD is caused by contact with infested water, originally presents as a rash and is associated with more serious issues, like lung lesions and neurological issues. The occurrence of CD in European recreational water bodies has led to the closure of holiday resorts and the decline in local economies.
Scotland has had several CD outbreaks, especially in Loch Lochore and Loch Lomond. Water sports in Scotland are an important part of the tourism industry. Identifying the risk of CD and implementing effective control is crucial for a sustainable recovery of the tourism industry, especially after the global COVID pandemic. It is paramount to identify the fluke species which could pose a public health threat.
To date we do not know:
- The full range of snail vectors that are able to transmit fasciolosis or avian blood fluke in the UK
- The distribution of their populations and the risk of contact in Scotland
- The other parasites they are transmitting, which could become an emerging health problem for humans and livestock
Bacterial food-borne diseases
Campylobacter and Salmonella are the leading causes of foodborne illness in Scotland. Both are notifiable and endemic, with exotic strains arriving continuously. In 2019, there were more than 700 human clinical cases of Salmonella infection reported. Campylobacter infections cost Scotland £3 million per year. Poultry meat is an important source of Campylobacter infections yet how these strains cause human disease is unclear. The production of cytolethal distending toxins (CDT) are potentially associated with human disease. For both Campylobacter and Salmonella, more evidence is required to inform future contingency plans, interventions, and surveillance so that threats and drug resistance are detected early.
Questions
- What approaches and strategies can combat zoonoses and emerging diseases to protect public health, animal health and antimicrobial resistance in Scotland?
Solutions
This project is assessing factors affecting the transmission of endemic zoonotic diseases and investigating potentially new and emerging pathogens. This broadly covers two main areas: 1) VBDs and emerging zoonoses, and 2) public health and bacterial food-borne diseases.
VBDs and emerging zoonoses
We are detecting and determining the distribution of snail-borne zoonotic and emerging trematodes of risk to human and animal health in Scotland and assessing novel control solutions. We are providing insights into risk factors leading to trematode infection and address Scotland’s capacity to effectively control these types of infections. We are also identifying zoonotic trematode species and accurately incriminating their aquatic snail vectors in Scotland. We are assessing the correlation between snail distribution, parasite transmission and connectivity between parasite populations. The latter is being measured using molecular population genetics to infer historical movement. We are also developing a cercariae (larval parasite) knockdown assay as an indicator of anthelmintic drug resistance and evaluating the potential of plant compounds as natural alternatives as sustainable, cost-effective, and eco-friendly alternatives to anthelmintics.
Public health and bacterial food-borne diseases
The second part of this project is identifying risk factors associated with Campylobacter detection in zoonotic etiopathogenesis. To do this, we are assessing and quantifying the transmission risk of Campylobacter for those working with poultry. This will help us understand the novel link between Campylobacter viability, virulence genotypes and storage conditions. Lastly, we are evaluating existing Scottish Salmonella whole genome sequence data and metadata. This is informing the development of effective and practical pre-harvest interventions to control the most important foodborne infections in poultry, pork and beef for the Scottish livestock industry.
Overall, we are helping to reduce the burden of disease in Scottish human and animal populations. This should lower health service costs and could save lives, safeguard trade and increase productivity.
Project Partners
Progress
Campylobacter jejuni
Theoretically it could be possible for the bacterium to be transmitted from poultry to food via personnel exposed to contaminated flock. We aim to investigate the likelihood of this risk during a total of two animal studies.
During the first study, we assessed the presence of the bacterium on the hands of farm staff after carrying out normal operations, under health and safety regulations, during the manipulation of birds infected with C. jejuni at day 21 of a simulated 35-day production cycle. Both social and ethical approvals to collect samples from staff (hand swabs) and the use of broiler chickens were obtained. Campylobacter jejuni concentration was not reported for any of the hand-swab samples throughout the study, indicating the absence of a contamination risk under the explored conditions.
For the follow-up study the plan is to compare C. jejuni concentration in the caecal content of chickens at different time-points with the concentration of the pathogen in environmental samples (i.e., drinking water, litter, ventilation-fan swab, door swab) and personnel (i.e., oral swab). We will also compare the expression level of different C. jejuni virulence and antimicrobial resistance genes in the same samples under different storage conditions, simulating and assessing the eventual risk for the consumer.
Evaluating the quality and utility of data from the Scottish Salmonella Reference Laboratory
In this work package we will focus on the genome sequence and epidemiological data from the Scottish Salmonella Reference Laboratory to identify and address key epidemiological questions. This work will be coupled with identifying effective pre-harvest interventions to control food borne zoonoses using RIBMINS (Risk-based meat inspection and integrated meat safety assurance) and the systematic review of literature. We have established a collaborative network with researchers and representatives from SRUC Veterinary Services, Public Health Scotland, BioSS (Biomathematics and Statistics Scotland) and Scottish Salmonella Reference Laboratory and have had several meetings. In doing so we have already identified a list of potential research questions that could be investigated through analysis of available Salmonella genome sequences and associated data from cases across Scotland. Three serovars have been identified to be prioritised at this stage including Salmonella Dublin, Salmonella Bovismorbificans and Salmonella Mbandaka. Publicly available sequence data has been acquired and descriptive analysis is underway. Out of the 815 publications retrieved during the initial stages of the systematic literature review, 170 have been classified as risk factor and prevalence studies. A mapping exercise and summarisation of the contents of these publications will be undertaken.
The results collected during this project will contribute to an increasing understanding of the risk factor (for both farm personnel and consumers) related not only to the presence of viable Campylobacter cells in several sample types, but also the level of danger represented by bacterial virulence and the eventual horizontal transmission of drug resistance.
Key outputs from the project
- The establishment of a multidisciplinary team across Scotland's Rural College including veterinarians, parasitologists, epidemiologists, social scientists and statisticians.
- The formation of a collaboration and data sharing agreement with the University of Alberta.
- Development of reference sequence data for medically important molluscs and the trematodes they transmit.
- Illustration that there is a lack of a link between Campylobacter jejuni transmission from poultry to handlers.
- Development of molecular screening protocols for the identification of virulence genes in these bacteria.
- Formation of collaborative links with the Salmonella Reference Laboratory.
Good practice
- This project worked alongside Rural and Environment Science and Analytical Services (RESAS) projects being conducted at the Moredun Institute so that resources, expertise, sampling efforts and biological materials could be shared.
- The involvement of international collaboration and application of existing resources to provide a local and global perspective of the diseases.
- Running animal trials alongside ongoing trials to reduce the impact on welfare and numbers of animals used in experiments.
- Taking a 'system' approach employing methods from classical microbiology, molecular biology, and animal trials.
- Utilizing a wide range of data sources already available, but which have not yet been analysed.
- The development of expert networks that link in with reference laboratories.
Challenges encountered
- The planning of field work due to delays in access to specific sites due to bird flu.
Recommendations from this project
- To gain the most out of ad hoc analyses of genomic data develop a key question which could be addressed before acquiring the data.
This project is now complete.
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