Lyme disease

Overview

•Most common vector-borne infection in the UK - caused by Borrelia burgdorferi, transmitted by Ixodes ricinus tick bites

•Tick must be attached ≥24-36 hours for transmission - prompt removal is highly effective

•Peak incidence April-October; high-risk areas include Scottish Highlands, New Forest, South Downs, Lake District

Presentation

•Erythema migrans (EM) - expanding flat/slightly raised red rash at bite site, appearing 3-30 days after bite; >5 cm diameter, often with central clearing ('bullseye'); usually painless and non-itchy - clinical diagnosis, no investigations needed

•Flu-like symptoms - fatigue, myalgia, arthralgia, headache, fever in early localised disease

•Facial nerve palsy - unilateral or bilateral LMN pattern; classic early disseminated feature

•Lyme neuroborreliosis - meningitis, radiculopathy (Bannwarth syndrome), encephalitis

•Lyme carditis - AV heart block (first to third degree), palpitations, syncope

•Lyme arthritis - mono/oligoarthritis of large joints (knee most common), late disease

•Acrodermatitis chronica atrophicans - late skin manifestation; bluish-red discolouration and atrophy on extremities (B. afzelii)

⚠️

A simple tick bite hypersensitivity reaction appears within hours, is <5 cm, and fades within 1-2 days. Erythema migrans appears days to weeks later, expands over time, and persists. This distinction drives the decision to treat.

Investigations

•EM present - no investigations required; treat clinically

•EM absent but Lyme suspected - two-tier serology:

•First-line: ELISA (IgM and IgG antibodies to Borrelia) - low sensitivity in first 4 weeks

•Confirmatory (gold standard): immunoblot (Western blot) - used only to confirm positive/equivocal ELISA, not standalone

•Repeat ELISA 4-6 weeks after first negative if still suspected and initial test was within 4 weeks of symptom onset

🎯

A negative ELISA within the first 4 weeks does NOT exclude Lyme disease - seroconversion may not yet have occurred. Repeat serology 4-6 weeks later if suspicion remains.

Management

•Early localised disease (EM) - treat in primary care with oral antibiotics:

•First-line: doxycycline 100 mg twice daily for 21 days

•Disseminated/neurological/cardiac/arthritic disease - specialist referral; IV ceftriaxone used for neuroborreliosis in secondary care

•Lyme carditis - may require temporary pacing; managed in cardiology

Prevention

•No licensed UK vaccine; prophylactic antibiotics after tick bite NOT routinely recommended in UK practice

•Wear long sleeves/trousers, tuck into socks; use DEET repellent on skin, permethrin on clothing

•Check whole body after outdoor exposure; pay attention to hairline, armpits, groin, behind knees

•Remove tick with fine-tipped tweezers close to skin, steady upward pull - do NOT crush, burn, or apply petroleum jelly

•Monitor for EM or flu-like symptoms for up to 30 days post-removal

Complications

•Post-treatment Lyme disease syndrome (PTLDS) - persistent fatigue, pain, cognitive symptoms >6 months after adequate treatment; prolonged further antibiotics are NOT recommended (no proven benefit, carry risks)