Lyme disease is caused by the spirochaete

Borrelia burgdorferi

and is spread by ticks.

Early features (within 30 days)

• erythema migrans (see: Erythema to compare with other lesions)
  • 'bulls-eye' rash is typically at the site of the tick bite
  • typically develops 1-4 weeks after the initial bite but may present sooner
  • usually painless, more than 5 cm in diameter and slowlly increases in size
  • present in around 80% of patients.
• systemic features
  • headache
  • lethargy
  • fever
  • arthralgia

Erythema migrans: Bulls-eye rash typically seen at the site of the tick bite

Later features (after 30 days)

• cardiovascular
  • heart block
  • peri/myocarditis
• neurological
  • facial nerve palsy
  • radicular pain
  • meningitis

ECG from a patient with Lyme disease showing 3rd degree heart block with LBBB indicating that the escape rhythm is from the right bundle - e Image used on license from Dr Smith, University of Minnesota

Investigation

• NICE recommend that Lyme disease can be diagnosed clinically if erythema migrans is present
  • erythema migrans is therefore an indication to start antibiotics
• enzyme-linked immunosorbent assay (ELISA) antibodies to Borrelia burgdorferi are the first-line test
  • if negative and Lyme disease is still suspected in people tested within 4 weeks from symptom onset, repeat the ELISA 4-6 weeks after the first ELISA test. If still suspected in people who have had symptoms for 12 weeks or more then an immunoblot test should be done
  • if positive or equivocal then an immunoblot test for Lyme disease should be done

Management of asymptomatic tick bites

• tick bites can be a relatively common presentation to GP practices, and can cause significant anxiety
• if the tick is still present, the best way to remove it is using fine-tipped tweezers, grasping the tick as close to the skin as possible and pulling upwards firmly. The area should be washed following.