Temporal and spatial drivers of Lyme disease hazard differ between urban and rural environments

Abstract

Our ability to predict how urban planning may influence public health and wellbeing is limited, because our understanding of the ecological drivers of key human diseases transmitted by wildlife vectors is poor in urban compared to rural environments. Here we examined how temporal and spatial ecological factors shape the environmental hazards of ticks and Lyme disease in urban greenspaces compared to rural environments. Deer space-use, Ixodes ricinus tick density and Lyme disease hazard were estimated at 60 urban greenspaces and 48 rural woodlands across 12 cities in the United Kingdom. Spatial and temporal metrics of urbanisation (built-up cover surrounding sites, extent of recent urbanisation, age of adjacent built-up area), woodland (tree cover) and connectivity, that were hypothesised to influence tick densities and Lyme disease hazard, were generated and their effects were tested using structural equation modelling. Nymphal ticks were detected in 73% of urban and 98% of rural sites, with nymph density and Lyme disease hazard were 3.6 and 5 times lower respectively in urban than rural woodlands. In cities, nymph density and Lyme disease hazard were positively correlated with tree cover within sites, connectivity to larger woodlands and negatively correlated with built-up cover surrounding sites and age of adjacent built-up cover. Conversely, in rural woodlands, woodland age was the strongest predictor of nymph density and Lyme disease hazard. These differences highlight the additional urbanisation-related pressures shaping urban tick and Lyme disease ecology, and the importance of the history of a site and its surroundings, which has strong implication for urban planning.

Dr Sara Gandy

Research Associate

My research primarily focuses on understanding the ecological drivers of tick-borne diseases to provide insights on the mechanisms involved in transmission cycles, especially on the interactions between ticks, hosts and pathogens. My research includes investigating the impacts of environmental changes (woodland restoration, rewilding) and host community composition (deer, rodent and birds) on tick-borne diseases risks in the UK. Some of my findings uncovered an opposing effect of deer densities on Lyme disease hazard through their positive effects on tick density and negative effects on infection prevalence. I also published work looking at spatiotemporal changes in tick distribution using passive surveillance data and I have been leading the National Tick Survey, which involves collaborating with stakeholders in thirty National Parks and recreational areas to collect ticks and test them for various tick-transmitted pathogens between 2021 and 2024. The goal is to understand disease hazard and temporal variation in areas visited by members of the public and deliver tick awareness messages.