Stat consult: Lyme disease

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The Lyme disease spirochete, Borrelia burgdorferi, is an obligate parasite.
The Lyme disease spirochete, Borrelia burgdorferi, is an obligate parasite.


  • most common tickborne infection in North America and Europe 

Also called

  • Lyme borreliosis


  • early Lyme disease

    • early localized Lyme disease—single erythema migrans (EM) lesion at site of tick bite
      • round, flat or raised, erythema expanding in diameter over days to weeks

      • may have area of central clearing ("target lesion") 

      • appears about 7 -14 days after tick detaches

      • often in axilla, back, abdomen, groin, and popliteal fossa

      • may also have
        • systemic symptoms (fever, chills, fatigue, arthralgias, or myalgias)

        • regional lymphadenopathy 

    • early disseminated Lyme disease
      • multiple EM lesions

      • early neurologic Lyme disease
        • cranial nerve palsy

        • meningitis

        • acute radiculopathy

        • mononeuropathy multiplex 

      • Lyme carditis - atrioventricular block and/or myopericarditis

    • borrelial lymphocytoma (rare)
      • cutaneous solitary bluish-red swelling < few centimeters in size

      • often due to Borrelia afzelii in Europe

  • late Lyme disease
    • Lyme arthritis
      • monoarticular or oligoarticular

      • affects knee, other large joints or TMJ

    • late neurologic Lyme disease
      • encephalomyelitis

      • encephalopathy

      • peripheral neuropathy

    • acrodermatitis chronica atrophicans

Estimated incidence

  • about 329,000 cases annually in US and 85,000 in Europe 

Associated conditions 

  • co-infection with anaplasmosis or babesiosis 

  • flaviviruses 


  • Borrelia burgdorferi sensu lato spirochete species complex

  • common species 

    • B. burgdorferi (USA)

    • B. afzelii (Europe)

    • B. garinii (Europe)

    • B. spielmanii and B. bavariensis


  • Ixodes ticks 

    • I. scapularis (previously I. dammini) in northeast and upper midwestern US (primarily transmits B. burgdorferi)

    • I. pacificus in western US (B. burgdorferi )

    • I. ricinus in Europe (B. garinii and B. afzelii )

    • I. persulcatus in Asia (B. garinii and B. afzelii )

  • reservoir hosts

    • I. scapularis
      • white-tailed deer 

      • small mammals, especially white-footed mouse

    • I. ricinus
      • large mammals (cattle, deer)

      • small rodents (wood mice, voles)

  • injection of nymphal tick saliva during feeding

    • I. scapularis and I. pacificus need 36-72 hours feeding to transmit enough spirochetes to cause infection 

    • B. afzelii transmission may be more rapid

  • nymphal tick activity most active late May-September

  • average incubation period 7-10 days


  • with EM, empiric diagnosis (compatible history, potential exposure, and exam findings) without testing

  • routine blood tests

    • WBC, hemoglobin, and platelets usually normal unless co-infection with Anaplasma phagocytophilum, Babesia microti, or tick-borne encephalitis virus 

    • LFTs slightly elevated in early disease

    • ESR elevations common, rarely > 80 mm/hour

  • for non-EM presentations, 2-tiered serologic testing recommended 

    • screening immunoassay—if negative, no further testing

    • if positive, supplementary Western blot
      • IgM positive when both
        • ≥ 2 of 3 specific bands present

        • duration of infection < 4 weeks

      • IgG positive when both
        • ≥ 5 of 10 specific bands present

        • duration of infection > 4 weeks

    • if negative in early Lyme disease, consider repeat testing 

  • other testing may include

    • CSF 

    • synovial fluid 

    • skin biopsy (rare)

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