Common species in Illinois
Illinois follows the shared source pattern. The species below are drawn from the state-authority sources listed in the sidebar Data Row.
- Brown dog tick
- Winter tick
- Gulf Coast tick (where IDPH or INHS document local establishment or expansion)
- Asian longhorned tick (animal/livestock context)
When ticks are most active
Blacklegged tick: nymph activity May through July and adult activity in spring and fall. American dog tick: most active spring through mid-summer, with May to early July as the practical peak. Lone star tick: April through late August where established, particularly in central and southern Illinois. Broad prevention caution spring through fall.
Where you're most likely to encounter ticks
Northern Illinois oak woodlands and forest-edge habitats, central and southern Illinois mixed hardwood forests and grassland-forest edges, Shawnee National Forest, prairie restoration sites, wooded and grassy trail edges, dog walking, hunting/camping, and yard work along wooded property edges.
Disease context
Each disease named below carries an evidence tag per the Data Row policy. Pills indicate the strength of state-specific evidence, not the severity of the disease. Symptoms should always be routed to a clinician; this is orientation, not diagnosis.
- Lyme diseasestate surveillance confirmed
- Rocky Mountain spotted feverstate surveillance confirmed
- Ehrlichiosisstate surveillance confirmed
- Anaplasmosisstate surveillance confirmed
- Tularemiastate surveillance confirmed
- Babesiosisregional pattern
- STARIregional pattern
- Alpha-gal syndromeregional pattern
- Heartland virus diseaseregional pattern
- Powassan virus diseasenon diagnostic mention only
If you find a tick — what to do
Map resolution notes
mixed resolution.IDPH, INHS, University of Illinois Extension, and CDC sources support state-level, regional (northern/central/southern Illinois), and some county-level statements, but not all species, disease, density, or expansion claims are county-supported. Use county-level claims only where an official county-level source supports that exact field; keep general species/range claims at state or regional level when the source resolution is broader.
State sources
- Primary species source
- Illinois Department of Public Health (IDPH) tick and tickborne disease pages for state species framing; Illinois Natural History Survey (INHS) Medical Entomology Laboratory and University of Illinois Extension for seasonal, habitat, and expansion nuance.
- Primary health source
- IDPH tickborne disease pages and clinician reference materials for disease and clinician-routing context; CDC tickborne disease pages for national context.
- Primary extension source
- University of Illinois Extension tick fact sheets and yard/landscape guidance, and INHS Medical Entomology tick resources, for species activity, habitat, prevention, and removal detail.
- Surveillance
- IDPH tickborne disease surveillance summaries, INHS tick surveillance data, CDC NNDSS for Lyme/RMSF/ehrlichiosis/anaplasmosis/tularemia counts, CDC Where Ticks Live, and University of Illinois Extension resources where map or surveillance context is used.