Ticks and zoonotic tick-borne pathogens in Scotland: evaluating risks for humans and livestock
Project Lead
Challenges
Tick populations and tick-borne disease (TBD) incidence have been increasing in recent times due to changes in climate, land, and behaviours. Globally, ticks are the second most important vector (i.e., organisms that transmit infectious pathogens) after mosquitoes. In the UK, ticks transmit tick-borne pathogens (TBPs), such as Lyme disease and the louping-ill virus. Environmental factors influence the risk of TBPs for livestock and humans. However, it is apparent that livestock and humans themselves are instrumental in changing tick and TBPs distribution.
The Covid-19 pandemic highlighted the need for further research into emerging and zoonotic pathogens, especially with alterations in land use and contact with farmed livestock and wildlife. Previous tick-related research has revealed important gaps in knowledge, especially concerning how humans and livestock interact with the environment to impact their own TBD risk. For example, by modifying habitats, management practices, and inducing fear of humans or competition with livestock.
We require more accurate and up-to-date models and risk maps. We have developed early risk maps which have been useful for identifying gaps in data, invalid assumptions, and methodological weaknesses. However, developing new state-of-the-art models and risk maps can overcome the shortfalls of previous models and better estimate tick abundance.
Questions
Solutions
This project adopts a One Health approach, focusing on how both humans and livestock interact with the environment to increase their interactions with ticks and TBP risk. Humans and livestock are crucial drivers of tick and pathogen-host distribution and abundance, and it may be more viable to focus on them for mitigating disease risk than the wider environment.
Our aim is to generate data by which to gain a further understanding of how humans and livestock interact with, and change, environmental factors to shape the risk of livestock and human zoonotic TBDs. This involves combining existing and new data to analyse how humans and livestock interact with environmental factors to shape their own exposure to zoonotic vector-borne pathogen risk.
Next, we are developing improved risk maps through spatial modelling. Our models enable us to assess the abundance and risk of ticks, and the zoonotic pathogens they transmit, across Scotland. We have benefitted from previous work which has highlighted shortcomings in predictive risk models, and the need to identify exactly where the strengths and weaknesses lie. Our new risk models are novel, improved and incorporate a wealth of new data. We are also providing additional capabilities for vector-borne pathogen molecular research to analyse further tick samples.
Project Partners
Progress
2023 / 2024
Key findings and outputs
Analysis of the meta database identified gaps in the understanding of ecological risk factors for Anaplasma phagocytophilum (AP) and enabled the testing of the augmentation and dilution hypothesis on its distribution in ticks, based on the presence of different hosts. Whereas deer were shown to be augmentation hosts, birds were proven to be dilution hosts which reduce AP prevalence in ticks. We were unable to show a significant effect of sheep presence/absence on AP prevalence in ticks (insufficient data). No significant effect of rodents on AP prevalence was found.
The analysis of existing Borrelia datasets allowed the testing of the landscape of fear hypothesis. A novel application of structural equation models was developed and using the collected data, we showed a very strong increase in deer space use further away from busy human trails, although more control sites with higher deer densities are needed to complete the model. The effect of proximity to humans in terms of number of nymphs is less strong and would benefit from additional data.
The third substantial output is the creation of additional VBD testing capacity at RAVIC.
Other outputs include 6 project-linked publications, 6 collaborations (including data sharing agreements), 17 engagement activities, participation in a Scottish Health Protection Network advisory committee, with a PhD project in progress.
Project insights
The gap analysis conducted in the first year was only possible as a result of the consent provided by other researchers to share their data. Thanks in part to the connections of one of the principal investigators on this project, data sharing agreements were implemented early in the project and the analyses could be carried out. Without these agreements, the start of the project would have been delayed. Data access and sharing agreements did not impact this project but could have repercussions for similar projects.
This project has been completed.
2022 / 2023
We have sourced nine large existing data sets on ticks, deer and ecological parameters, and these are now being checked, standardised and combined. This initial work, mainly carried out by a PhD student appointed within the project, will next aim to produce a complete large meta-database including tick and spatial environmental information from across Scotland, spanning 15 years. This will form the basis for the mathematical models which will be developed in the following years. Some of these models will combine human and livestock spatial information to explore human and livestock associations with ticks and pathogens. Other models will produce distribution maps of TBPs and their relationship with different environments and hosts. Additionally, the maps will highlight areas of overlap between ticks, wildlife, livestock and humans, to identify potential areas of higher risk for human and livestock exposure to ticks and TBDs. The accessibility of some of the spatial data required for the distribution map models has already been confirmed.
The COVID epidemic has exposed how important it is not to be dependent on limited or unique infrastructure. The research on ticks and their associated pathogens is currently carried out in a single research facility in Scotland. Therefore, to increase capacity and to allow for future-proofing, a second facility (housed at the Rural and Veterinar Innovation Centre (RAVIC), Scotland's Rural College) has been created, this facility is capable of investigating not only ticks but also other disease vectors (midges/mosquitoes/snails). This required refurbishing and setting up a laboratory, sourcing equipment and preparing test protocols. Most of the initial protocols were shared with the new facility by the current laboratory. The new facility has begun testing ticks and the presence of TBPs.
Impact resulting from this project
We already have established links with Lyme disease policy practitioners through membership of the Scottish Health Protection Network's Lyme Borreliosis group. Discussion with Public Health Scotland representatives on possible risk of exposure to tick-borne encephalitis virus and louping-ill virus in Scotland have also taken place.
Previous Projects
Related Projects
Disease mechanisms
Disease mechanisms: The aim of this work is to provide increased understanding of how pathogens (viruses, bacteria and parasites) interact with their host to cause disease. This new knowledge will underpin the development of next-generation control strategies for a range of infectious diseases of importance to livestock production both nationally and internationally.
Novel Vaccines
The aim of this RD is to develop safe, highly effective, optimised, novel vaccines for the control of the most production- and welfare-limiting endemic diseases of Scottish livestock. The key drivers for this research are: