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Lyme Disease

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Overview

Also known as Lyme borreliosis, Lyme disease is an infection caused by the spirochaete (spiral-shaped bacterium) Borrelia burgdorferi, which is mainly transmitted by tick bites.

It is characterised by early and late features involving the skin, nervous system, heart, eye, and joints and was discovered in Old Lyme, Connecticut.

Pathophysiology

Once Borrelia burgdorferi enters the body, it may be cleared by the immune system, resulting in a person being asymptomatic but seropositive.

Borrelia burgdorferi does not produce toxins and it is thought that the manifestations seen are due to the immune response. In some cases, it can spread and trigger immune responses, giving rise to the symptoms seen, such as erythema migrans, which is thought to be due to inflammation in response to it. It can spread to distal sites including the nervous system, heart, and joints, leading to disseminated disease.

Epidemiology

  • Very few ticks in the UK are infected with Borrelia burgdorferi, so most tick bites do not cause Lyme disease
  • Its incidence may be around 2 per 100,000 per year

Risk Factors

  • Exposure to ticks – such as occupation/recreational exposure to woodlands and fields
  • Longer tick bite duration – transmission of Borrelia burgdorferi from ticks can require longer than 48 hours

Presentation

The features of Lyme disease can be seen in three stages. The first stage is early localised (<36 days):

  • Erythema migrans – a bulls-eye rash seen at the site of the tick bite:
    • The most common first manifestation (~80%)
    • Usually visible from 1-2 weeks
    • Usually painless, expands over days-weeks, and is not usually itchy
  • Non-specific symptoms (~1/3 of people) – often similar to a viral infection including:

Early disseminated (after weeks/months):

Late persistent (after months-years):

  • Features include arthritis (may be migratory), acrodermatitis chronica atrophicans (blue-red discolouration of the extensor surfaces), encephalomyelitis, psychosis, and vertigo.

Investigations and Diagnosis

Overview

Lyme disease is diagnosed clinically if erythema migrans is present. If not an enzyme-linked immunosorbent assay (ELISA) for Borrelia burgdorferi antibodies is first-line:

  • If positive or equivocal, arrange an immunoblot test
  • If negative but clinical suspicion is high, retest ELISA4-6 weeks later:
    • If still negative but suspected in someone with symptoms >12 weeks, arrange immunoblot testing

Management

Suspected or confirmed Lyme disease

In patients with confirmed or highly suspected Lyme disease:

  • Early disease:
    • 1st-line: doxycycline
    • Alternative options include amoxicillin and if this is unsuitable, azithromycin
  • Disseminated disease (e.g. central nervous system/cardiac/joint involvement etc.):
    • 1st-line: IV ceftriaxone

A Jarisch-Herxheimer reaction may occur in up to 15% of people during the first 24 hours of treatment. This occurs due to the release of cytokines when antibiotics kill large numbers of bacteria and is characterised by fever, rash, and tachycardia 1-12 hours after antibiotics. It is also seen in Syphilis and usually resolves within 24-48 hours.

Tick bites

Ticks should be removed as soon as possible using the following:

  • Grasp the tick as close to the skin as possible with fine-tipped tweezers
  • Pull upwards and firmly without twisting to avoid mouthparts remaining in the skin
  • Clean the skin with water and antibacterial soap

Antibiotic prophylaxis for tick bites is not routinely recommended.

Complications

  • Neurological complications – meningitis, encephalitis, radiculitis, peripheral neuropathy, facial nerve palsy
  • Cardiac complications – heart block, myocarditis
  • Acrodermatitis chronic atrophicans – blue-red discolouration and swelling of the skin, which can be come atrophic over time and be associated with neuropathy and arthritis
  • Lyme arthritis – usually mono-/oligoarticular and often large joints such as the knee or hip
  • Persisting non-specific symptoms – fatigue, malaise, myalgia. This is sometimes known as post-treatment Lyme disease or chronic Lyme disease, but this is controversial

Prognosis

  • Antibiotics are highly effective, reduce the risk of further symptoms developing, and increase recovery. Most people recover completely if treated appropriately.
  • Complete response rates may be as high as 90% in people with erythema migrans

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