As climate change warms the planet, a new study led by 91亚色 postdoctoral fellow Marco Tosato examines the risks and potential solutions associated with a growing consequence: the spread of disease-carrying ticks into new regions.
鈥淐limate change is rapidly expanding habitats for ticks and mosquitoes across Canada, driving up rates of Lyme disease and introducing newer threats like anaplasmosis into regions where they weren't previously seen,鈥 says Tosato, who works through the Faculty of Science's Laboratory of Industrial and Applied Mathematics (LIAM).
As a result, researchers and public health officials are increasingly looking for ways to reduce tick populations and the diseases they spread.
One approach is the use of prescribed burns, also known as controlled fires. Previous research has shown they can reduce tick numbers, but whether those reductions translate into lower disease risk remains less clear. Researchers know less about how different fire regimes affect disease spread when accounting for the complex interactions between ticks, wildlife hosts and the pathogens they carry.
鈥淚f we want to predict disease risks down the line, we really need to understand how all these moving parts interact,鈥 says Tosato, whose previous work has evaluated different tick-control strategies such as acaricides and repellents.
Tosato and collaborator Kyeongah Nah, from the National Institute for Mathematical Sciences in South Korea, sought to address those questions. They wanted to better understand how controlled burns affect the spread of tick-borne diseases while accounting for factors that have received less attention in previous models, including the role of rodents and whether fire affects young and adult ticks differently.
, the study was supervised by Professor Jianhong Wu through the LIAM lab and used a mathematical model representing ticks, rodents and the diseases that can spread between them. The model simulated how tick populations change over time, how they interact with rodents and how infections move through those populations. It also distinguished between infected and uninfected ticks and rodents, allowing the team to track transmission under different conditions.
The researchers then introduced fire as a variable, simulating prescribed burns with different frequencies and effectiveness levels. This allowed them to test a wide range of hypothetical scenarios, including how disease spread might change if burns occurred more or less frequently, or removed larger or smaller proportions of tick and rodent populations. By running thousands of simulations, the team could compare different fire-management approaches and their potential effect on disease risk.
Before evaluating the effectiveness of controlled burns, the simulation revealed several factors that play an outsized role in disease spread.
One practical finding was that not all ticks contribute equally to transmission. The researchers found that adult ticks and rodents played especially important roles in driving disease transmission. That suggests control strategies targeting those populations may have the greatest impact on limiting transmission.
The model also highlighted the importance of a lesser-understood transmission pathway known as co-feeding. This occurs when infected and uninfected ticks feed close together on the same animal, allowing disease to spread directly between the ticks even if the host itself is not infected. When the researchers incorporated this process into their modelling approach, disease became considerably harder to control. Infections persisted under conditions where they otherwise would have disappeared.
With those transmission dynamics established, the researchers examined how prescribed burns influence disease risk.
The simulations suggested that prescribed fire can substantially reduce the spread of tick-borne diseases, particularly when carried out regularly. The modelling also highlighted the importance of burn frequency. Relatively modest reductions in tick populations achieved through annual burns produced effects comparable to much more aggressive interventions carried out less often.
At the same time, the model suggested that completely eliminating tick populations would be difficult. Doing so would require highly effective burns at frequent intervals, conditions that may be impractical or potentially harmful to natural ecosystems. Instead, reducing disease risk may be a more realistic goal.
The researchers conclude that prescribed fire could serve as a flexible management tool that supports both ecosystem stewardship and public health goals. However, they caution that its effectiveness depends on factors such as local ecological conditions, the characteristics of the disease being targeted and how frequently burns are conducted.
The team also recommends further research examining how prescribed burns compare with other tick-control strategies, including repellents and acaricides, as well as how longer-term environmental changes caused by burning, such as shifts in vegetation cover and humidity, affect tick survival and disease transmission.
For Tosato, the study demonstrates the importance of understanding the connection between environmental change and disease risk.
鈥淚 hope it highlights how fire dynamics and land management can influence these systems, encouraging a broader perspective on how environmental changes and disease transmission connect,鈥 he says.
The work also underscores the role mathematics can play in addressing emerging public-health challenges. By simulating complex ecological interactions that are difficult to study directly, mathematical models can help researchers anticipate future risks and evaluate potential responses.
鈥淎s changing environmental conditions allow ticks and new pathogens to establish themselves in regions where they previously couldn't survive, a close collaboration between mathematics and public health is essential to generate actionable insights that allow us to stay ahead of emerging threats,鈥 Tosato says.