- Clinical science
Lyme disease (or borreliosis) is a tick-borne infection caused by certain species of the Borrelia genus (B. burgdorferi in the US), a genus of facultative intracellular bacteria. There are three stages of Lyme disease. Stage I (early localized disease) is characterized by erythema migrans (EM), an expanding circular red rash at the site of the tick bite, and may be associated with flu‑like symptoms. In stage II (early disseminated disease), patients may present with neurological symptoms (e.g., facial palsy), migratory arthralgia, and cardiac manifestations (e.g., myocarditis). Stage III (late disease) is characterized by chronic arthritis and CNS involvement (late neuroborreliosis) with possible progressive encephalomyelitis. Lyme disease is a clinical diagnosis in patients presenting with EM. Serological tests (e.g., Western blot; enzyme-linked immunosorbent assay) can help support the clinical diagnosis, especially if the presence of EM is not known or questionable. Lyme disease is treated with antibiotics; the drugs of choice are doxycycline for localized disease and ceftriaxone for disseminated disease.
- Incidence: most commonly reported vector-borne disease in the US
- Geographical distribution: primarily the Northeast and upper Midwest
Epidemiological data refers to the US, unless otherwise specified.
- Various tick species: mainly Ixodes scapularis (deer or black-legged tick); in the northeastern and upper midwestern US
- Typically found in forests or fields on tall brush or grass
- The incidence of Lyme disease is highest between April and October (especially from June to August).
- Peromyscus leucopus, the white‑footed mouse, is the primary reservoir of B. burgdorferi in the US.
Increased risk of disease for:
- Outdoor workers (landscapers, farmers, etc.)
- Outdoor enthusiasts (i.e., hikers, hunters, etc.)
Stage I (early localized Lyme disease)
- Symptoms develop within 7–14 days after a tick bite.
Erythema chronicum migrans (EM)
- Occurs in 80% of infected individuals
- Usually a circular, slowly expanding red ring around the bite site with central clearing
- Typically warm, painless
- EM is often the only symptom.
- Self-limiting (typically subsides within 3–4 weeks)
- Flu‑like symptoms
Stage II (early disseminated Lyme disease)
- Symptoms develop 3–10 weeks after a tick bite
- Migratory arthralgia that can progress to Lyme arthritis
- Early neuroborreliosis
- Risk of cardiac arrhythmias (e.g., AV Block) and rarely myopericarditis
- Multiple erythema migrans lesions
- Ocular manifestations: including conjunctivitis, retinal vasculitis, optic neuropathy, and uveitis
Stage III (late Lyme disease)
- Symptoms develop months to years after the initial infection
- Chronic (10% of cases)
- Late neuroborreliosis manifestations include:
- In Europe and Asia: acrodermatitis chronica atrophicans (ACA, also called Herxheimer's disease)
- Chronically progressive dermatological disease due to infection with Borrelia afzelii that occurs only in Europe and Asia and most commonly affects among women > 40 years of age
- Manifestation on the extensor side of extremities
- Stages in the course of the disease:
- After a tick bite, observe for erythema chronicum migrans. Suspicious rashes may be monitored over several days.
- If the patient history and clinical presentation indicate Stage I Lyme disease, empiric antibiotics may be started without further testing.
- If symptoms of Lyme disease arise in a patient with possible exposure (especially if a history of recent travel to an area with high vector density) → conduct two-step serological testing
- If signs of neuroborreliosis are present and other tests are inconclusive, consider additional procedures, such as a lumbar puncture for cerebrospinal fluid testing.
Two‑step serological testing
- Initial test: enzyme‑linked immunosorbent assay (ELISA)
- Confirmatory test: Western blot
- Detect IgG and IgM antibodies against Borrelia
- Results are only significant with corresponding clinical symptoms because:
- Positive results only demonstrate exposure to Borrelia (not necessarily current infection).
- False negative results are possible if seroconversion has not yet occurred (may take up to 8 weeks).
- Various diseases can lead to a false positive serology as a result of cross-reactions, including:
- Cerebrospinal fluid testing
- Commonly conducted if signs of arthritis are present, but results do not allow differentiation from septic arthritis without PCR
- Synovial fluid findings
- For erythema migrans
- For Lyme carditis
- For Lyme arthritis
- For neuroborreliosis
The differential diagnoses listed here are not exhaustive.
|Tick-borne diseases (endemic to US) ||Pathophysiology / Epidemiology|| |
|Lyme disease|| |
|Tick paralysis|| |
|Rocky Mountain spotted fever (RMSF)|| |
|Tick-borne relapsing fever |
|Stages||Presentation||General therapy||Therapy in pregnant/nursing patients|
|Localized Lyme disease|
|Disseminated Lyme disease|| |
If infection is likely (e.g., EM is present) → start antibiotic treatment!
- There is no approved vaccine on the market.
- Avoid areas known for Lyme disease.
- Prevent and properly manage tick bites to avoid exposure.
- Wear protective clothing: e.g., long-sleeved shirts, long pants, and light colors.
- Use tick repellent and pesticides.
- Check body for tick bites.
- Remove ticks immediately!
- Grasp the tick with tweezers directly above the skin's surface.
- Carefully pull upward with even pressure.
- Do not use nail polish remover, adhesives, oils, or similar substances to remove the tick. The tick should be removed quickly rather than waiting for it to detach slowly.
- Disinfect the site of the bite and dispose of the tick
- Observe the bite site for early detection of EM.