almostadoctor app banner for android and iOS almostadoctor iPhone, iPad and android apps almostadoctor iOS app almostadoctor android app


Borrelia Burgdorferi (spirochaete)
Incubation: 7-14 days


Animal hosts=deer/rodents


Commonest vector borne illness in USA
Focally endemic in woodland of north America – infections mostly occur in summer.


  • Tick bite
  • B. burgdorferi¬†is injected into the skin in tick saliva
  • This contains substances that disrupt the immune response at the bite site
  • Allows infection establish
  • The bacteria multiply in the¬†dermis
  • Host inflammatory response causes circular EM lesion
  • Spirochaetes spread via the bloodstream.

The spirochetes may avoid the immune response by a form of molecular mimicry, causing a pathogen-induced auto-immune disease by causing inflammatory substances such as cytokines.

Clinical features

  • Early localized:
  • Skin reaction around bite site (erythema migrans)
  • Regional lymphadenopathy
  • Fever
  • Headache

Early disseminated

  • Arthralgia
  • Malaise
  • Pronounced systemic reaction
  • Carditis (sometimes with AV conduction defects)
  • Neurological involvement


  • Polyneuritis
  • Arthritis
  • Encephalopathy
  • Acrodematitis chronic atropicans


Primarily clinical diagnosis, confirmed by antibody detection.
Culture from biopsy


Doxycycline/amoxicillin (14 days, longer if disseminated)
IV cefotaxime in neurological disease


  • Protective clothing/insect repellants
  • Special care in handling and allowing outdoor pets inside homes
  • Prompt remova of attatched ticks
  • Reduction in the number of primary hosts for the tick(i.e. rodents, other small mammals, and deer)


Read more about our sources

Related Articles