Deer tick
Ixodes scapularis
Established in Pennsylvania
- Size:
- Small, a sesame seed (nymph: a poppy seed)
- Look for:
- Reddish-orange body, solid dark shield, black legs, no pattern
- Carries:
- Lyme, babesiosis, anaplasmosis, Powassan
Tick Identification in Pennsylvania
The ticks you are most likely to find in Pennsylvania, with photos and the size, color, and markings that tell them apart. Only the deer tick carries Lyme disease. Below the chart, see which types live in your county.
Carries Lyme
American dog tick
Dermacentor variabilis
Established in Pennsylvania
- Size:
- Larger, an apple seed
- Look for:
- Brown with an ornate off-white mottled shield
- Carries:
- Rocky Mountain spotted fever, tularemia (rare)
Lone star tick
Amblyomma americanum
Established in Pennsylvania
- Size:
- Medium, rounded
- Look for:
- Reddish-brown; female has a single white dot on the back
- Carries:
- Ehrlichiosis, STARI, alpha-gal syndrome
Brown dog tick
Rhipicephalus sanguineus
Found nationwide, the one tick that infests homes and kennels indoors
- Size:
- Medium, narrow body that tapers toward the head
- Look for:
- Uniform reddish-brown, no ornate markings
- Carries:
- Rocky Mountain spotted fever, canine diseases
Gulf Coast tick
Amblyomma maculatum
A southern tick spreading north into the mid-Atlantic
- Size:
- Large, bigger than a lone star
- Look for:
- Silvery ornate markings on the shield, no single dot
- Carries:
- Rickettsia parkeri spotted fever
Asian longhorned tick
Haemaphysalis longicornis
A newer arrival, established in the mid-Atlantic and spreading north
- Size:
- Small and plain, often found in large numbers
- Look for:
- Reddish-brown with no markings
- Carries:
- Mainly a livestock threat; human disease risk under study
Rocky Mountain wood tick
Dermacentor andersoni
Not established in Pennsylvania
- Size:
- Larger, an apple seed
- Look for:
- Brown with an ornate off-white and gray marbled shield
- Carries:
- Rocky Mountain spotted fever, Colorado tick fever, tularemia
Pacific Coast tick
Dermacentor occidentalis
Not established in Pennsylvania
- Size:
- Larger, an apple seed
- Look for:
- Brown with a marbled silvery-gray ornate shield
- Carries:
- Pacific Coast tick fever, tularemia
Pennsylvania establishment is shown for the three ticks CDC tracks by county; the others carry a regional range note. Source: CDC tick surveillance (ArboNET Tick Module), 2025. County surveillance is coarse: “not established” is a lack of records, not proof a tick is absent.
Deer, dog and lone star ticks by Pennsylvania county
These are the three ticks CDC maps county by county, not the only ticks in Pennsylvania: the brown dog, Gulf Coast, and Asian longhorned ticks are in the chart above. Tap a county for its daily tick-risk detail.
| County | Deer tick | American dog tick | Lone star tick |
|---|---|---|---|
| Adams County | Established | Established | Reported |
| Allegheny County | Established | Reported | Reported |
| Armstrong County | Established | Reported | Not established |
| Beaver County | Established | Established | Not established |
| Bedford County | Established | Established | Reported |
| Berks County | Established | Established | Not established |
| Blair County | Established | Reported | Not established |
| Bradford County | Established | Reported | Not established |
| Bucks County | Established | Established | Established |
| Butler County | Established | Reported | Not established |
| Cambria County | Established | Reported | Reported |
| Cameron County | Established | Not established | Not established |
| Carbon County | Established | Established | Not established |
| Centre County | Established | Reported | Not established |
| Chester County | Established | Established | Established |
| Clarion County | Established | Reported | Not established |
| Clearfield County | Established | Reported | Not established |
| Clinton County | Established | Reported | Not established |
| Columbia County | Established | Established | Not established |
| Crawford County | Established | Reported | Not established |
| Cumberland County | Established | Established | Reported |
| Dauphin County | Established | Established | Established |
| Delaware County | Established | Established | Established |
| Elk County | Established | Not established | Not established |
| Erie County | Established | Established | Established |
| Fayette County | Established | Established | Not established |
| Forest County | Established | Reported | Not established |
| Franklin County | Established | Established | Established |
| Fulton County | Established | Reported | Not established |
| Greene County | Established | Established | Not established |
| Huntingdon County | Established | Established | Not established |
| Indiana County | Established | Reported | Reported |
| Jefferson County | Established | Reported | Not established |
| Juniata County | Established | Established | Not established |
| Lackawanna County | Established | Established | Not established |
| Lancaster County | Established | Established | Not established |
| Lawrence County | Established | Reported | Not established |
| Lebanon County | Established | Established | Established |
| Lehigh County | Established | Established | Reported |
| Luzerne County | Established | Reported | Not established |
| Lycoming County | Established | Established | Not established |
| McKean County | Established | Reported | Not established |
| Mercer County | Established | Reported | Not established |
| Mifflin County | Established | Reported | Not established |
| Monroe County | Established | Established | Not established |
| Montgomery County | Established | Established | Reported |
| Montour County | Established | Established | Not established |
| Northampton County | Established | Established | Not established |
| Northumberland County | Established | Established | Not established |
| Perry County | Established | Established | Not established |
| Philadelphia County | Established | Established | Established |
| Pike County | Established | Established | Reported |
| Potter County | Established | Reported | Not established |
| Schuylkill County | Established | Established | Not established |
| Snyder County | Established | Established | Reported |
| Somerset County | Established | Reported | Not established |
| Sullivan County | Established | Established | Not established |
| Susquehanna County | Established | Established | Not established |
| Tioga County | Established | Not established | Not established |
| Union County | Established | Established | Not established |
| Venango County | Established | Reported | Not established |
| Warren County | Established | Reported | Not established |
| Washington County | Established | Established | Not established |
| Wayne County | Established | Established | Not established |
| Westmoreland County | Established | Reported | Not established |
| Wyoming County | Established | Reported | Not established |
| York County | Established | Established | Reported |
Lone star ticks and alpha-gal syndrome
The lone star tick is established in Pennsylvania in 8 of 67 counties (see the table above). Its bite can cause alpha-gal syndrome, an allergy to red meat.
Do not overlook the tiny ones
Nymph deer ticks are the size of a poppy seed and cause most Lyme cases in Pennsylvania because they are so easy to miss. When you check for ticks, look for the small ones too, especially in June and July.
Frequently asked questions
- What types of ticks live in Pennsylvania?
- Pennsylvania has the deer tick (blacklegged tick), which carries Lyme disease and is established across the state; the American dog tick, which is established; and the lone star tick, which is established and causes alpha-gal syndrome. County-level presence is shown in the table above.
- Which Pennsylvania tick carries Lyme disease?
- The deer tick, also called the blacklegged tick, is the tick that spreads Lyme disease in Pennsylvania. The American dog tick and lone star tick do not carry Lyme, though they can transmit other illnesses.
- Are there lone star ticks in Pennsylvania?
- Yes. The lone star tick is established in Pennsylvania, in 8 of the state's 67 counties (Bucks County, Chester County, Dauphin County and more, listed in the table above). It causes alpha-gal syndrome, a red-meat allergy.
- How can I tell these ticks apart?
- Use size, color, and legs. The deer tick is small with a reddish-orange body, a solid dark shield, and black legs. The American dog tick is larger and brown with an ornate off-white mottled shield. The female lone star tick has a single white dot on her back. The chart above shows each one.