Research into zoonoses and emerging diseases to protect public health and animal health in Scotland

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 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

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 distributing 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.