>ED Rounds – Lyme Disease – Dr Paul Frankish

Lyme Disease: Update and recent controversies

Presented by Dr Paul Frankish

 

 


 Link to NB Health Lyme Disease Information


Transmission

  • Borrelia burgdorferi
  • Tick-borne spirochetal bacteria
  • Ixodes scapularis and Ixodes pacificus
  • Field mice, birds and white-tailed deer

Discovered in Lyme, Connecticut  by Dr. Burgdorfer, investigating an abnormal cluster of juvenile RA. Other common tick-borne illnesses are transmitted through the lone star tick (Amblyomma americanum) and the American dog tick (Dermacentor variabilis) that transmit ehrlichiosis and Rocky Mountain spotted fever, respectively.  The ticks serve as the vector between the animal population and humans.  Deer are the preferred host for ticks, and the tick population is highest when deer are present, but the actually pick up the Borrelia from small mammals mostly.


Identification

A) is an Argasid (soft tick, Ornithodoros turicata)

B) has a scutum, long body butshort mouth parts (dog tick, Dermacentor variabilis)

C) is Ixodes scapularis(!)

D) has a scutum, but has a short and stout body – it also has a “lone star” on its body (lone star tick, Amblyomma americanum)


Erythema Migrans Pearls

  • Often just a macule with no central clearing (20-30%)
  • Classically 1-2 weeks from time of tick bite, but anywhere from 3-30 days
  • Some patients may either not have it or notice it
  • May have multiple lesions
  • Rashes within 2 days are usually an immune reaction to tick saliva


Clinical Pearls

  • Always take clinical context into consideration
  • If IgM positive and IgG negative greater than 4 weeks since infection, likely false positive
  • Do not use the test in the setting of EM rash
  • Consider testing if all satisfied:
    • Lyme endemic area
    • Risks for exposure
    • Any features of disseminated or late disease

Testing


Prophylaxis

  • Common ED presentation
  • If attached less than 36 hrs or not Ixodes scapularis, then risk is very low
  • Criteria for prophylaxis (need all)3:
    • Ixodes scapularis
    • Attached longer than 36 hrs
    • Prophylaxis within 72 hrs of removal
    • Greater than 20% local tick infection rate
  • Single dose of Doxycycline 200 mg or 4mg/kg for children greater than 8 years old
  • Children < 8yrs
    • Not sufficient evidence to recommend any other regimes
    • A “watch and wait” approach is recommended in these cases

Full Presentation with Notes

Download (PDF, 4.33MB)


NB Health Lyme Disease Update Jan 2017

Download (PDF, 190KB)

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