Disease-carrying ticks are predicted to spread, globally

Ticks carry serious diseases such as Lyme, anaplasmosis, babesiosis and encephalitis, which are predicted to pose a mounting threat to human and animal health, due to shifting ecosystems and species ranges.

Chinese researchers have developed the most comprehensive modelling yet of where harmful disease-carrying ticks are likely to thrive in the future. Until now, there has been insufficient information on their distribution. The research underscores the need for coordinated, climate-informed surveillance and control strategies.

The new modelling revealed the biggest current risks to be concentrated in warm-temperate regions of the Northern Hemisphere – most notably China, the United States and parts of Europe. The highest risk regions for future expanding tick colonisation in Europe were France (with an area of nearly 620,000 km² suitable for ticks) and Spain (506,000km² suitable), followed by Ukraine, Germany, Italy, Poland, Romania and the UK. Between 50% (UK) and 95% (Spain) of land in these countries offers habitat classed as being of medium-high suitability for ticks.

The team modelled current and future habitat suitability for 28 key pathogen-carrying tick species, and their diseases. They combined ecological, climate and socio-economic data. The study projected changes in tick distribution and disease risk under multiple environmental change scenarios up to the year 2100. They compiled over 70,000 tick records from China, database searches and literature reviews. 

They projected future tick habitat suitability based on 11 environmental variables, including sunlight, temperature and precipitation. Future models also factored in plausible alternative socioeconomic futures and their effects on climate change, and combined this information with land use and human population density data, to assess tick risk in different regions.

Current tick distribution is linked with temperature and precipitation patterns, with the amount of sunlight in January emerging as the most influential environmental factor. For example, the brown dog tick Rhipicephalus sanguineus, found in Europe, spreads Rocky Mountain spotted fever and typhus to humans. It needs significant amounts of January sunshine to thrive. 

In the Northern Hemisphere, more winter sunshine helps ticks to overwinter, however too much strong sunshine in summer is not ideal for them. Across Africa, a few tick species are adapted to higher temperatures. The tick Hyalomma lusitanicum is abundant in Algeria and Tunisia, while R. microplus and R. sanguineus are widely distributed in Ghana and Nigeria.

The findings suggest that monitoring and prevention strategies should concentrate on areas that provide suitable conditions for ticks in January, as well as in summer.

The researchers used a ‘Maxent’ model[1] to make future projections of habitat suitability for ticks, under different emissions scenarios. Suitable habitat is likely to be lower under lower greenhouse gas emission scenarios, but could increase significantly under higher greenhouse gas emissions. Crucially, each tick species responds differently to climate variables, indicating that local and species-specific monitoring will be necessary.

The findings have clear implications for global public health and environmental governance. If tick ranges continue to expand, so too will the risk of tick-borne diseases.

This trend necessitates proactive policy responses including enhanced disease surveillance and region-specific approaches to ticks and disease management, such as educational outreach and habitat management aimed at controlling tick populations. Specifically, France, the UK, Germany, and Spain have substantial areas of medium and high suitability that warrant further attention in the future, say the researchers.

This work addresses the critical need for cross-sector strategies linking health, climate and biodiversity policies that are responsive to changing socio-economic factors such as population density and land use. 

The modelling framework could by applied in other research topics too – such as understanding human population and land use change dynamics, and in other zoonotic and climate-sensitive disease management, such as COVID-19 and monkeypox.

The research presents one of the most robust forecasts of tick range expansion to date, identifying where and how public health threats from tick-borne diseases will intensify. The researchers acknowledge, however, that future land uses are uncertain, and current datasets may not fully capture the spectrum of ecological interactions. For example, changes in host availability. Integrating tick suitability predictions with anticipated land use change would be useful, they noted, as would considering human population dynamics, and areas of increased human-tick interaction, in risk assessments.

Reference:

Cao, B., Bai, C., Wu, K., La, T., Chen, W., Liu, L., Zhou, X., Chen, C., Li, X., Su, Y., Che, L. and Li, G. (2025) Ticks jump in a warmer world: Global distribution shifts of main pathogenic ticks are associated with future climate change. Journal of Environmental Management 374 (2025): 124129. https://doi.org/10.1016/j.jenvman.2025.124129

[1] Maxent, short for Maximum Entropy, is a software application that utilizes a maximum entropy approach to model species niches and distributions