Lyme disease

Definition
Lyme disease is a multisystem infectious disease caused by the spirochete Borrelia burgdorferi sensu lato complex, transmitted to humans primarily through the bite of infected Ixodes ticks (commonly known as deer ticks or black-legged ticks). It typically manifests in stages, ranging from localized skin involvement to disseminated systemic disease affecting joints, the nervous system, and the heart.

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Epidemiology

• Most common vector-borne illness in North America and Europe.

• In the United States, highest incidence is reported in the Northeast, upper Midwest, and Pacific Northwest.

• Transmission occurs mainly during late spring and summer, coinciding with nymphal tick activity.

• Risk is higher in wooded, grassy, and rural areas.

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Etiology and Pathogen

• Caused by spirochete bacteria in the Borrelia burgdorferi sensu lato group:

  • B. burgdorferi sensu stricto (most common in North America).

  • B. afzelii and B. garinii (predominant in Europe and Asia).

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Transmission

• Spread through the bite of infected Ixodes species ticks.

• Transmission risk increases if tick is attached for ≥36 hours.

• No person-to-person transmission documented.

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Pathophysiology

After tick inoculation, the spirochete multiplies locally in the skin and can spread hematogenously to multiple organs. Immune response and bacterial persistence contribute to inflammation and tissue damage in joints, nervous tissue, and myocardium.

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Clinical Stages

1. Early Localized Disease (Days to Weeks after Tick Bite)

• Erythema migrans (EM): Expanding, erythematous rash with central clearing (“bull’s-eye” appearance) at the site of the tick bite; not always present.

• Flu-like symptoms: Fever, chills, malaise, headache, myalgia, arthralgia.

2. Early Disseminated Disease (Weeks to Months after Infection)

• Multiple EM lesions.

• Neurological involvement: Facial nerve palsy (bilateral possible), meningitis, radiculoneuritis.

• Cardiac manifestations: Atrioventricular block, myocarditis, pericarditis.

3. Late Disseminated Disease (Months to Years after Infection)

• Intermittent or persistent arthritis, especially in large joints (knee most common).

• Chronic neurological symptoms: Polyneuropathy, encephalopathy.

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Complications

• Chronic arthritis.

• Persistent neuropathic pain.

• Post-treatment Lyme disease syndrome (PTLDS) with fatigue, pain, and cognitive difficulties despite antibiotic therapy.

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Diagnosis

Clinical Diagnosis

• In early localized stage with typical EM, diagnosis is clinical — lab confirmation not required.

Laboratory Confirmation (in later stages or atypical presentations)

• Two-tiered serologic testing:

  • Enzyme immunoassay (EIA) or immunofluorescence assay (IFA) → if positive or equivocal → Western blot.

• CSF analysis for neuroborreliosis: Lymphocytic pleocytosis, elevated protein, intrathecal antibody production.

• ECG for suspected cardiac involvement.

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Management

1. Early Localized Disease

• Doxycycline: Adults – 100 mg orally twice daily for 10–14 days; children ≥8 years – 4 mg/kg/day in 2 divided doses (max 100 mg/dose) for 10–14 days.

• Amoxicillin: Adults – 500 mg orally three times daily for 14 days; children – 50 mg/kg/day in 3 divided doses (max 500 mg/dose) for 14 days.

• Cefuroxime axetil: Adults – 500 mg orally twice daily for 14 days; children – 30 mg/kg/day in 2 divided doses (max 500 mg/dose) for 14 days.

2. Early Disseminated Disease

• Neurological (meningitis, cranial neuropathy): IV ceftriaxone 2 g once daily for 14–21 days (children: 50–75 mg/kg/day up to 2 g).

• Carditis: Oral doxycycline or IV ceftriaxone depending on severity; treat for 14–21 days.

3. Late Disseminated Disease

• Arthritis: Oral doxycycline 100 mg twice daily for 28 days; if inadequate response, IV ceftriaxone 2 g daily for 14–28 days.

• Chronic neuroborreliosis: IV ceftriaxone for 2–4 weeks.

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Post-Exposure Prophylaxis

• Doxycycline 200 mg orally as a single dose (children ≥8 years: 4 mg/kg up to 200 mg) within 72 hours of tick removal, if:

  • Tick identified as Ixodes species.

  • Estimated attachment ≥36 hours.

  • Prophylaxis can start within 72 hours.

  • Local infection rate of ticks with Borrelia ≥20%.

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Supportive Care

• Analgesics: Paracetamol 500–1000 mg every 4–6 hours (max 4 g/day) or ibuprofen 400–600 mg every 6–8 hours (max 2.4 g/day) for pain and fever.

• Physical therapy for joint recovery in late-stage arthritis.

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Prevention

• Protective clothing in tick-endemic areas.

• Use of DEET-containing repellents.

• Tick checks and prompt removal with fine-tipped tweezers.

• Landscape modifications to reduce tick habitats.