Deer tick
Ixodes scapularis
Not established in Montana
- 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 Montana
The ticks you are most likely to find in Montana, 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
Reported in Montana
- 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
Not established in Montana
- 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
Established in Montana
- 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 Montana
- Size:
- Larger, an apple seed
- Look for:
- Brown with a marbled silvery-gray ornate shield
- Carries:
- Pacific Coast tick fever, tularemia
Montana 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 Montana county
These are the three ticks CDC maps county by county, not the only ticks in Montana: 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 |
|---|---|---|---|
| Beaverhead County | Not established | Reported | Not established |
| Big Horn County | Not established | Reported | Not established |
| Blaine County | Not established | Reported | Not established |
| Broadwater County | Not established | Reported | Not established |
| Carbon County | Not established | Reported | Not established |
| Carter County | Not established | Reported | Not established |
| Cascade County | Not established | Reported | Not established |
| Chouteau County | Not established | Reported | Not established |
| Custer County | Not established | Reported | Not established |
| Daniels County | Not established | Reported | Not established |
| Dawson County | Not established | Reported | Not established |
| Deer Lodge County | Not established | Reported | Not established |
| Fallon County | Not established | Reported | Not established |
| Fergus County | Not established | Reported | Not established |
| Flathead County | Not established | Reported | Not established |
| Gallatin County | Not established | Reported | Not established |
| Garfield County | Not established | Reported | Not established |
| Glacier County | Not established | Reported | Not established |
| Golden Valley County | Not established | Reported | Not established |
| Granite County | Not established | Reported | Not established |
| Hill County | Not established | Reported | Not established |
| Jefferson County | Not established | Reported | Not established |
| Judith Basin County | Not established | Reported | Not established |
| Lake County | Not established | Reported | Not established |
| Lewis and Clark County | Not established | Reported | Not established |
| Liberty County | Not established | Reported | Not established |
| Lincoln County | Not established | Reported | Not established |
| Madison County | Not established | Reported | Not established |
| McCone County | Not established | Reported | Not established |
| Meagher County | Not established | Reported | Not established |
| Mineral County | Not established | Reported | Not established |
| Missoula County | Not established | Reported | Not established |
| Musselshell County | Not established | Reported | Not established |
| Park County | Not established | Reported | Not established |
| Petroleum County | Not established | Reported | Not established |
| Phillips County | Not established | Reported | Not established |
| Pondera County | Not established | Reported | Not established |
| Powder River County | Not established | Reported | Not established |
| Powell County | Not established | Reported | Not established |
| Prairie County | Not established | Reported | Not established |
| Ravalli County | Not established | Reported | Not established |
| Richland County | Not established | Reported | Not established |
| Roosevelt County | Not established | Reported | Not established |
| Rosebud County | Not established | Reported | Not established |
| Sanders County | Not established | Reported | Not established |
| Sheridan County | Not established | Reported | Not established |
| Silver Bow County | Not established | Reported | Not established |
| Stillwater County | Not established | Reported | Not established |
| Sweet Grass County | Not established | Reported | Not established |
| Teton County | Not established | Reported | Not established |
| Toole County | Not established | Reported | Not established |
| Treasure County | Not established | Reported | Not established |
| Valley County | Not established | Reported | Not established |
| Wheatland County | Not established | Reported | Not established |
| Wibaux County | Not established | Reported | Not established |
| Yellowstone County | Not established | Reported | Not established |
Do not overlook the tiny ones
Nymph deer ticks are the size of a poppy seed and cause most Lyme cases in Montana 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 Montana?
- Montana has the deer tick (blacklegged tick), which carries Lyme disease and is not established across the state; the American dog tick, which is reported; and the lone star tick, which is not established and causes alpha-gal syndrome. County-level presence is shown in the table above.
- Which Montana tick carries Lyme disease?
- The deer tick, also called the blacklegged tick, is the tick that spreads Lyme disease in Montana. The American dog tick and lone star tick do not carry Lyme, though they can transmit other illnesses.
- Are there lone star ticks in Montana?
- The lone star tick is not established in Montana in current CDC county surveillance, but ranges are expanding northward, so this can change. 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.