Lyme Disease Flashcards
What are the leading tickborne diseases?
Lyme disease (Borrelia burgdorferi) Rocky Mountain Spotted Fever (Rickettsia rickettsii) Ehrlichiosis (Ehrlichia chaffeensis) Anaplasmosis (Anaplasma phagocytophilum) Babesiosis (Babesia microti)
What tick transmits Lyme disease?
Blacklegged tick (or deer tick) (Ixodes scapularis)
What organism causes Lyme Disease?
The spirochete Borrelia burgdorferi
Where does Lyme disease occur?
North America (North East), Europe, Asia
What is erythema migrans (EM)?
The target rash that occurs in 70-80% of cases
Onset: 7-14 days after bite and expands over days
Rarely painful
(Rash will not always have the classic target appearance, so be mindful of that during exam!! May be multiple lesions, disseminated, blistering, blue-red, etc.)
What are early disseminated manifestations of Lyme Disease?
Neurologic: meningitis, cranial nerve palsies, motor/sensory radiculoneuropathy
-Facial palsy (summer months; may be b/l)
Carditis: heart block
Ocular: optic neuropathy or uveitis
What are late disseminated manifestations of Lyme Disease?
May occur months to a few years after onset of infection and not necessarily preceded by early localized or disseminated Lyme disease
Arthritis: intermittent or persistent in few large joints (especially knee)
Neuro: chronic axonal polyneuropathy (spinal radicular pain or distal paresthesias)
What is the two-tiered testing for Lyme Disease?
First Test: Enzyme Immunoassay (EIA) or Immunofluorescence Assay (IFA)
- Quantitative to determine if antibody levels are elevated
- If negative, consider alternative diagnosis OR if pt has s/sx of Lyme disease for <30 days, consider obtaining convalescent serum
Second Tests:
IgM and IgG Western Blot
-If first test positive or equivocal and s/sx for <30 days
IgG Western Blot ONLY
-If first test positive or equivocal and s/sx for >30 days (because IgM is only meaningful during acute illness)
Is the 2-tier testing good at detecting early disease?
NO
In acute EM (early stage of the disease), patients who have been ill less than a few weeks, only 38% will test positive on the testing!
Thus, a negative test does not exclude a diagnosis in early stage
So, in patient with EM and exposure in endemic area, you can skip the test (it will probably be negative)
Is the 2-tier testing good at detecting late disease?
Yes!
In patients who have been ill longer than a few weeks, a negative test strongly suggests against infection
Stats: pts with arthritis (97% test positive) and with late neuro (100% test positive)
What are additional tests for Lyme disease?
- Single-tier Western blot (without EIA)
- Capture assays for antigens
- Lymphocyte transformation tests
- CD57 lymphocyte assays
- Novel culture techniques
[all have questionable utility, very little validation and can lead to misdiagnosis and improper treatment]
What is the prognosis for Lyme disease?
- Most patients treated with ABx recover completely
- May have persistent or recurrent joint swelling…and re-treatment may be necessary
- May have persistent inflammatory sx of fatigue post-treatment: muscle aches, reduced concentration, malaise…BUT extended therapy shows no benefit
- Persistent sx are more common in pts diagnosed in late stage of disease
What is the treatment?
Amoxicillin 500 mg TID
Doxycycline 100 mg BID (not for kids <8yrs)
Cefuroxime axetil 500 mg BID
Alternative:
Selected macrolides, Ceftriaxone 2 g IV QD, Cefotaxime 2 g IV q8hrs, or Penicillin G 18-24 million U/day IV
When would you give antibiotic prophylaxis?
ONLY IF ALL of the criteria are met:
- Highly endemic area
- Attached tick identified as I. scapularis
- Attached for >36 hours
- Treatment can be started within 72hrs of exposure
- No contraindications to treatment
Dose: 200 mg doxyxycling PO x1 (for adults)
