Lyme Disease
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Lyme Disease is a multi-system bacterial infection caused by the spirochaete Borrelia burgdorferi. It is the most common tick-borne disease in the Northern Hemisphere.
The "Great Imitator"
Like Syphilis (another spirochaete), Lyme Disease has distinct stages and can mimic many other conditions (from Fibromyalgia to Multiple Sclerosis) in its later stages.
Clinical Scenario: The Hiker's Rash
A 45-year-old man presents with a large red ring on his thigh. He noticed a 'small bug' there 2 weeks ago while hiking in the New Forest. He has a mild headache and feels 'flu-like'.
Key Teaching Points
- The rash is **Erythema Migrans** (Bullseye Rash).
- It is pathognomonic.
- **Action**: Start Doxycycline immediately. **Do NOT wait for blood tests** (antibodies take weeks to develop; testing now will likely be negative/false negative).
Image Integration Plan
| Image Type | Source | Status |
|---|---|---|
| Management Algorithm | AI-generated | PENDING |
| Pathophysiology (Tick Cycle) | AI-generated | PENDING |
| Clinical Photo (Erythema Migrans) | Web Source | PENDING |
| Tick ID (Ixodes Ricinus) | Web Source | PENDING |
[!NOTE] Image Generation Status: Diagrams illustrating the Tick-Mouse-Deer cycle are queued.
Diagnostic Two-Tier System
Only use if Erythema Migrans is absent.
- ELISA (C6): High sensitivity screening test.
- Immunoblot (Western Blot): High specificity confirmatory test. (Only done if ELISA +ve).
- Vector: Ixodes ticks (Sheep tick / Deer tick).
- Nymphs (poppy seed size) are main vectors (spring/summer).
- Need to be attached for > 24 hours to transmit bacteria.
- Geography:
- UK: New Forest, Scottish Highlands, Lake District.
- USA: Northeast and Midwest.
- Europe: Central Europe / Scandinavia.
- Innoculation: Tick saliva injects Borrelia.
- Local Spread: Bacteria migrate centrifugally through skin -> Rash (Erythema Migrans).
- Dissemination: Via blood/lymph to Heart, Joints, Nervous System.
- Immune Evasion: Borrelia can change surface proteins (VlsE) to evade the immune system.
Stage 1: Early Localised (3–30 days)
Stage 2: Early Disseminated (Weeks–Months)
Stage 3: Late Disseminated (Months–Years)
- Skin: Full body check for EM rash (hidden areas: groin, axilla, hairline).
- CN Exam: Facial weakness.
- Joints: Swollen knee?
- Heart: Irregular pulse (block)?
Diagnosis is Clinical if Erythema Migrans is present.
Serology (If no rash)
- Timing: Antibodies take 4-8 weeks to develop. Testing too early causes False Negatives.
- Protocol:
- Test 1: C6 ELISA.
- Test 2: Immunoblot. (If ELISA positive or equivocal).
- If Negative but high suspicion (e.g. < 4 weeks symptoms): Repeat in 4-6 weeks.
Other
- ECG: Essential if palpitations/syncope.
- LP: If meningitis suspected (CSF shows lymphocytosis + intrathecal antibody production).
A. Early Lyme (Skin Rash)
- Doxycycline 100mg BD for 21 days.
- Alternative: Amoxicillin (Pregnancy/Children) or Azithromycin.
- Jarisch-Herxheimer Reaction: Worsening of symptoms in first 24h as bacteria die. (Warn patient).
B. Neuroborreliosis / Carditis
- IV Ceftriaxone 2g OD for 21-28 days.
- (Or high dose oral Doxycycline - evidence suggests equal efficacy for mild-moderate neuro disease).
C. Chronic Lyme?
- "Post-Treatment Lyme Disease Syndrome" (PTLDS) exists (fatigue/pain persisting after cure).
- However, Chronic active infection is controversial and prolonged antibiotics are NOT recommended by guidlines (high risk, no benefit).
- Permanent Joint Damage.
- Facial Palsy: Usually recovers but can take months.
- Heart Block: Might require temporary pacing.
- Excellent if treated early.
- Re-infection is possible (immunity is not lifelong).
- NICE NG95: Lyme disease (2018).
- IDSA Guidelines.
What is Lyme Disease? It is an infection passed on by ticks. Ticks live in long grass and woodland.
What to look for? The classic sign is a Bullseye Rash (a red ring that spreads outwards). It looks like a target. It appears 1-4 weeks after a bite. You might also feel like you have the flu.
Can it be serious? If treated early, it is easily cured. If missed, the bacteria can spread to the nerves (causing a droopy face) or the heart (causing dizzy spells).
How do you treat it? A course of antibiotics (usually Doxycycline) for 3 weeks.
How to remove a tick?
- Use fine-tipped tweezers.
- Grasp the tick as close to the skin as possible (the head).
- Pull upwards with steady pressure.
- Do NOT twist it (the head might break off).
- Do NOT burn it or use vaseline.
- NICE. Lyme disease [NG95]. 2018.
- Steere AC, et al. Lyme borreliosis. Nat Rev Dis Primers. 2016.
- Wormser GP, et al. The clinical assessment, treatment, and prevention of lyme disease (IDSA Guidelines). Clin Infect Dis. 2006.