Could global warming cause a range expansion or shift of Lyme disease in the U.S. state of Maryland? A mathematical modeling approach

Lyme disease, transmitted by ticks, is endemic in several regions of the United States (including the Northeast), and the lifecycle of ticks is significantly affected by changes in local climatic variables. In this study, we modeled the dynamics of Lyme disease across the U.S. state of Maryland. We used a mechanistic model, calibrated using case and temperature data, to assess the impact of temperature fluctuations on the geospatial distribution and burden of Lyme disease across Maryland. Our results demonstrate that tick activity and Lyme disease intensity peak when temperature reaches 17.0°C—20.5°C. We estimate that moderate projected global warming will cause a range expansion of Lyme disease, increasing burden in Central Maryland and extending risk into Western counties, while reducing the disease burden in Southern and most Eastern counties. High projected warming will cause a westward shift, with new Lyme disease hotspots emerging in Western counties, and reduction of burden in Central, Southern and Eastern regions. Maryland will experience reductions in overall Lyme disease burden under both projected global warming scenarios (with more reductions under the high warming scenario). Disease elimination is feasible using a hybrid strategy, which combines rodents baiting, habitat clearance, and personal protection against tick bites, with moderate coverages.