Lyme disease (LD) is a bacterial infection caused by the spirochete Borrelia burgdorferi, transmitted to humans through the bite of infected ticks. It is the most commonly reported vector-borne disease in the United States, though its prevalence varies dramatically across regions. Initial symptoms often include a characteristic skin rash, along with non-specific flu-like complaints such as fever and fatigue. If untreated, the infection can spread to cause complications affecting the joints, heart, and nervous system. Understanding the local risk of tick-borne illnesses is important for public health.
Lyme Disease Presence and Vector Ticks in Missouri
Lyme disease is present in Missouri, but the state is officially classified as a low-incidence area compared to highly endemic states in the Northeast and Upper Midwest. The primary vector is the Blacklegged tick (Ixodes scapularis), also known as the deer tick. These ticks are present throughout Missouri, particularly in wooded and brushy areas, though their populations are not as dense as in higher-incidence regions. The low incidence is partly due to a low rate of the pathogen found within the local Blacklegged tick population. The Missouri Department of Health and Senior Services reports cases that meet the surveillance criteria established by the Centers for Disease Control and Prevention (CDC).
Common Tick-Borne Diseases in Missouri
Ehrlichiosis
The risk of contracting other tick-borne illnesses is significantly higher in Missouri than that of Lyme disease. The most prevalent diseases include Ehrlichiosis and Rocky Mountain Spotted Fever (RMSF), which are transmitted by different tick species. Ehrlichiosis is the most commonly reported tick-borne disease in Missouri, vectored by the aggressive Lone Star Tick (Amblyomma americanum). Symptoms often include fever, headache, and muscle aches, but typically lack the characteristic bullseye rash seen in Lyme disease.
Rocky Mountain Spotted Fever and STARI
RMSF is transmitted by the American Dog Tick (Dermacentor variabilis). While RMSF shares general flu-like symptoms with other tick-borne diseases, it can present with a non-itchy rash that typically begins on the wrists and ankles. The Lone Star tick is also associated with Southern Tick-Associated Rash Illness (STARI). STARI produces a bullseye-like rash and symptoms similar to early Lyme disease, but it does not cause the same long-term neurological or arthritic complications.
Recognizing Infection and Seeking Diagnosis
The most recognizable early sign of Lyme disease is the Erythema Migrans (EM) rash, a localized skin lesion that expands to create a characteristic “bullseye” appearance. This rash occurs at the site of the tick bite in 60 to 80% of infected individuals, typically appearing within three to 30 days. General systemic symptoms can accompany the rash, including fever, headache, fatigue, stiff neck, and muscle or joint pain.
If a tick bite is followed by these symptoms, immediate medical evaluation is warranted. Diagnosis commonly follows the CDC’s two-tiered testing protocol: an initial screening (EIA or IFA), followed by a confirmation Western blot if the first test is positive or indeterminate.
Diagnosing Lyme disease in Missouri is challenging, as many local bullseye-like rashes are ultimately diagnosed as STARI. Physicians must carefully evaluate symptoms, exposure history, and laboratory results against strict CDC case definitions. The prevalence of other tick-borne diseases also requires a broad differential diagnosis.
Practical Tick Prevention and Removal
Preventing tick bites is the most effective way to avoid all tick-borne illnesses. When spending time outdoors, applying chemical repellents containing DEET to exposed skin or treating clothing with permethrin can significantly reduce the risk of attachment. Staying on marked trails and avoiding dense brush and tall grass also minimizes exposure to tick habitats.
After outdoor activity, a thorough check of the body and clothing should be performed immediately, as an infected tick must typically be attached for at least 24 hours to transmit the bacterium. If a tick is found attached, it should be removed quickly and correctly. Use fine-tipped tweezers to grasp the tick close to the skin’s surface and pull upward with steady, even pressure, avoiding twisting or jerking. Following removal, clean the bite area with soap and water or an antiseptic.