Tick Species in Missouri: Which Ones Bite and Which Carry Disease

Missouri has more tick species than most northern states — the state's position at the convergence of several ecological zones means residents encounter a variety of ticks, some of which carry serious diseases. Identifying which tick bit you is relevant medical information, particularly when deciding whether to monitor for symptoms or seek preventive treatment. Here is a guide to Missouri's most important tick species.

American Dog Tick (Dermacentor variabilis)

The American dog tick is Missouri's most commonly encountered tick on humans and dogs. Adults are medium-large — females can reach 15mm when engorged — and are reddish-brown with distinctive white or silver mottling on the back (scutum). They are most active spring through early summer and are found in grassy, shrubby areas along trails, roadsides, and field edges.

Disease Risk

• Rocky Mountain Spotted Fever (RMSF): The most serious disease carried by this tick in Missouri. Despite the name, RMSF is common in the southeastern and south-central United States, and Missouri reports cases annually. RMSF can be fatal if not treated promptly with antibiotics. Early symptoms include fever, headache, and rash.
• Tularemia: A bacterial infection transmissible through tick bites; also contracted through contact with infected animals.

Lone Star Tick (Amblyomma americanum)

The lone star tick is extremely common in Missouri and is an aggressive biter — all three life stages (larva, nymph, adult) readily bite humans. Adults are reddish-brown; females are identified by a single white spot (the "lone star") on the center of their back. Larvae, called "seed ticks," are tiny and can attach in large numbers, causing intense itching.

Disease Risk

• Ehrlichiosis: Missouri is one of the highest-reporting states for ehrlichiosis, which is primarily transmitted by lone star ticks. Symptoms include fever, headache, muscle aches, and fatigue, typically beginning 1 to 2 weeks after a bite.
• Heartland virus: A relatively recently identified viral illness transmitted primarily by lone star ticks in Missouri and nearby states. Cases have been reported in Missouri.
• STARI (Southern Tick-Associated Rash Illness): A Lyme-like illness associated with lone star tick bites; produces a bull's-eye rash but is caused by a different organism than Lyme disease.
• Alpha-gal syndrome: Lone star tick bites have been associated with development of an allergy to red meat (alpha-gal). This is a permanent immune response that causes allergic reactions when red meat is consumed.

Blacklegged Tick / Deer Tick (Ixodes scapularis)

The blacklegged tick is smaller than the other species — adults are about 3–5mm unfed — with an orange-brown body and darker (black) legs. It is the primary vector of Lyme disease in the eastern United States. It is present in Missouri but less abundant than the lone star or American dog tick, being more common in the forested northern and eastern portions of the state.

Disease Risk

• Lyme disease: Missouri is on the western edge of the established Lyme disease range. Cases are reported but at lower rates than in northeastern states. The risk is real, particularly in wooded areas with abundant white-tailed deer and white-footed mice (the primary reservoir hosts).
• Anaplasmosis: A bacterial infection with symptoms similar to ehrlichiosis.

Brown Dog Tick (Rhipicephalus sanguineus)

The brown dog tick is unique in being able to complete its entire life cycle indoors — it can establish infestations inside homes and kennels, particularly in areas used by dogs. It is reddish-brown and narrow compared to other species. It rarely bites humans but can transmit RMSF when it does. Infestations in homes associated with dogs may require professional treatment of the interior.

The Importance of Prompt Tick Removal

Many tick-borne diseases require extended attachment time for transmission — Lyme disease typically requires 24 to 48 hours of attachment before the bacteria can be transmitted. Prompt, proper removal reduces disease risk significantly. See our article on what to do after a tick bite for removal guidance and when to seek medical care.