vectorborne diseases Flashcards
what is the most common vector-borne dz in the US?
lyme dz
how is lyme dz transmitted?
Borrelia burgdorferi via Ixodides, a small tick
how long must the tick feed to transmit the spirochete?
24-36 hours
what is the first stage of a lyme dz infection?
early localized infection that occurs 7-10 days after the original bite
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describe stage 1 of lyme dz
- erythema migrans: flat or slightly raised red lesion that expands over several days, typically with central clearing (bull’s eye) -about 25% of pts done have this
- common sites are the groin, thigh, axilla, and it typically resolves in 3-4 weeks w/o tx
- 50% of pts experience flu like sx
stage 2 of lyme dz?
early disseminated infection that occurs days to weeks later
what are the clinical manifestations of lyme dz
- involve the skin, CNS, MSK system
- HA, stiff neck, fatigue, malaise, intermittent musculoskeletal sx
- cardiac: pericarditis, arrhythmias, heart bock
- neurologic: aseptic meningitis, bell palsy, encephalitis
what is stage 3 of lyme dz?
late persistent infection that occurs months to years later
what occurs in stage 3 of lyme dz?
- MSK dz, CNS and PNS,
- skin manifestations
what are MSk dz sx of late persistent lyme dz?
joint pain w/o objective findings, frank arthritis, chronic synovitis
most likely immunologic cause
what are CNS adn PNS sx of late persistent lyme dz?
- subacute encephalopathy (memory loss, mood change)
- axonal polyneruopathy (paresthesias, encephalopathy)
- leukoencphalitis (cognitive change, paraparesis, ataxia, bladder dysfxn)
what are skin manifestations of stage 3 lyme dz?
acrodermatitis chronicum atropicans: bluish-red discoloration of distal extremities w/ atropy (seen in europe, not in US)
dx studies for lyme dz
antibody testing via immunofluorescent assay or ELISA techniques
western as confirmatory test
when will IgM go away in lyme dz? IgG?
after 6-8 weeks; will last indefinitely
problems with diagnostic testing in lyme dz
-tests lack sensitivity: the probability of a false-positive test may be greater than that of a true-positive test
what dz may cause fals-positive tests for lyme dz?
RA, SLE, mono, endocarditis
what should early lyme dz dx be based on?
clinical presentation
how is late dz dx lyme
by objective evidence of clinical manifestations and laboratory evidence of dz
what are other lab tests that can be done for lyme
-CSF, synovial fluid analysis, aspirations, or bx
how is lyme dz treated (early dz)
- doxy
- alternatives: amoxicillin, cefuroxime, ceftriaxone, cefotaxime