Borrelia (spirochaete) infection, spread by ticks (Ixodes), common in localized areas of Europe and North America (forest environments).

Differential includes possible co-infection from other tick born organisms viz anaplasmosis, or babesiosis.

Vaccine available if likely to be at risk.

Clinical

Skin – Erythema migrans is the classic skin lesion, a spreading ring usually at the site of the bite but can be multiple and at different sites.  Develops over a week or two, up to 40 days, can last months.  Looks like erythema multiforme, but time scale different.  Any insect bite hypersensitivity will look similar.  Lyme lymphocytoma is a painless bluish red nodule or plaque, especially on the ear but also reported on the nipple and scrotum.  More common in children.  May persist for months, can precede other features.  Acrodermatitis chronica atrophicans (ACA) is almost exclusively seen in adults, predominantly women, and is an eruption with chronic, progressive red or bluish-red lesions, usually on the extensor surfaces, with later atrophic, fibroid or sclerodermic changes.

Arthritis – uncommon, presents as recurrent inflammation of 1 or more large joints, usually the knee. Swelling can be disproportionate to pain.  Can become more persistent – in a minority, despite treatment, inflammation becomes chronic (presumably immune-mediated).

Carditis occurs rarely, and almost always with other clinical features.  Usually partial heart block, but can be complete, usually resolves within a week.

Neurological – isolated facial palsy, meningitis, other cranial nerve palsies, meningoencophalitis, polyradiculopathy.  There is a small proportion of children who can present with non-specific headache, fatigue, neck pain without clear neurological signs (and also the rare case of raised intracranial pressure).

Other rare disease manifestations include uveitis, iridocyclitis and keratitis.

Diagnosis

For erythema migrans, clinical diagnosis is adequate, and antibodies only positive in 30-70% anyway!  If atypical, do acute and convalescent serology.  Current tests have reasonable  sensitivity and specificity, if done acutely with high probability cases.  However, false negatives possible in early disease, especially in EM and early neurological.  Early antibiotic treatment is also believed to potentially block antibody production.

For early neuroborreliosis, antibodies 80% sensitive, rises to virtually 100% for late or ACA.

Antibodies can then persist for months or even years after successful treatment of the infection, so repeat testing is not useful for monitoring treatment success.

First line ELISA test can have false positives for other spirochaetes, glandular fever and autoimmune conditions.

Western blot for IgM is done as a second line test for ambivalent cases to increase specificity, but cut offs for both serology and Western blot can be an issue though, with potential false positives for other acute infections and autoimmune conditions.  Definitely needs to be an approved lab . [European Union Concerted Action on Lyme Borreliosis (EUCALB) initiative criteria, Clin Microbiol Infect 2011; 17: 69–79, DOI: 10.1111/j.1469-0691.2010.03175.x]

The idea that there are seronegative “chronic Lyme” cases has little evidence to support it, with only 2 possible cases reported (ACA and arthritis, not neuro).

Consider PCR on skin biopsy, synovial fluid/tissue. Not great for CSF.  Culture is difficult.  CSF antibodies for neuroborreliosis; consider for isolated facial palsy.

Treatment

The most commonly recommended first-line treatments for different stages of Lyme borreliosis in Europe are:

• Erythema migrans/borrelial lymphocytoma:  10-14 days Doxycycline if 9yr+ (initially 5 mg/kg in 2 divided doses on day 1, then 2.5 mg/kg daily in 1–2 divided doses, max dose 200mg, for a total of 21 days, option for higher dosing) – 10 days courses of doxy effective in US trials.  Else Amoxicillin 50mg/kg/d, max 500mg TDS (10-14 days)[BNFc says 30mg/kg/d, max 1g, TDS for 21 days].  Don’t delay treatment pending test results.  Scandinavia use 10 days Pen V (100mg/kg/d, max 1000mg TDS). BNFc says Azithromycin as alternative.
• Isolated facial palsy: 14 days Oral doxycycline  – else as above.  Doesn’t probably help resolution but may prevent later complications.
• Meningitis/radiculopathy: PO Doxycycline or IV Ceftriaxone  50-100mg/kg/d, max 2g daily (14-21 days). [BNFc talks about CNS disease separate from cranial/peripheral nerves]
• Encephalitis, myelitis: Ceftriaxone (14 days)
• Lyme arthritis: Doxycycline (28 days) else Amoxicllin (21-28 days)
• Carditis: Ceftriaxone during pacing, else PO doxycycline (14 days)