Overview

• Researchers analyzed records from 2018–2022 and mapped three tick species across Illinois, publishing the findings in Ticks and Tick-borne Diseases.
• Ten southern counties—Union, Johnson, Hardin, Jackson, Williamson, Saline, Franklin, Hamilton, Jefferson, and Perry—formed lone star tick clusters that match Illinois Department of Public Health high-ehrlichiosis designations.
• Deer tick clusters were identified in Macon, Piatt, Champaign, and Douglas counties in central Illinois and in Cook, DuPage, and Kendall in the northeast, alongside 1,728 Lyme, 81 anaplasmosis, and 23 babesiosis cases recorded statewide from 2018–2022.
• Dog tick hotspots included Pope and Hardin in the south and Piatt and Moultrie in the center, with southern Illinois recording 350 Rocky Mountain spotted fever group rickettsiosis cases.
• Active surveillance collected 1,414 ticks from 80 of 102 counties, and researchers warn that data gaps in 22 counties complicate risk targeting despite guidance emphasizing clothing barriers, permethrin-treated gear, and post-hike tick checks.