02-21 Lyme Disease

Question 1

Ecological hypothesis for increasing rate of Lyme disease?

Answer 1

New England had been historically deforested —New, less thick forest → ↑ light to forest floor → ↑ ground cover → ↑ deer → ↑ ticks → ↑ Lyme

Question 2

OBJECTIVE: epidem of lyme

Answer 2

Peak is June and July (nymphs are feeding)

Most common vector-borne disease in the U.S., but most cases occur in these areas [see map]

• N.E./eastern sea board (MA to GA) I. scapularis
• Midwest, WI and MN Ixodes scapularis
• West, CA and OR Ixodes pacificus

Question 3

OBJECTIVE: clinical features of lyme

• Localized Stage 1
• Disseminated Stage 2

Answer 3

Incubation period of 3-32 days

• Localized Stage 1:
  
  • erythema chronica migrans (indurated center)
  • f/c, malaise, fatigue, arthralgias, & adenopathy
• Disseminated Stage 2: The great imitation
  
  • MSK: 60% migrating arthritis
  • CNS: 10% triad
    
    • aseptic meningitis
    • cranial neuritis (Bell’s palsy)
    • peripheral neuropathy (assymetric, motor & sensory)
  • derm: 2° annular lesion, smaller than 1
  • Cor: heart block

Question 4

OBJECTIVE: What systems are involved in late Lyme dz?

Answer 4

Chronic/Stage 3 Lyme

Begins after 6-12 monts

• Derm: Acrodermatitis chornic migrans [seen here; eMedicine] morphea
• CSN: subacute encephalopathy, peripheral neuropathy
• MSK: chronic arthritis in a few large jts

Question 5

OBJECTIVE: prevention of Lyme

Answer 5

PREVENTION

• wear long pants
• control pets
• DEET
• permetherin-coated clothing
• do tick checks/shower w/ a wash cloth w/in 24 hours
  
  • tick has to feed on your for > 24 hrs before transmitting the spirochete
• vaccine wasn’t 100% effective, ?allergic rxns and didn’t cover other tick-borne dzs
• remove ticks from the base (don’t squeeze belly → contents into wound)

Question 6

OBJECTIVE: tx of Lyme

Answer 6

EARLY

doxycycline, amoxicillin, or cefuroxime

LATE

doxy, penicillin G, ceftriaxone

Question 7

OBJECTIVE: What is the differential Dx of disease following a tick bite?

Answer 7

• Babesiosis
• Ehrlichiosis
• Anaplasmosis
• Rocky Mountain Spotted Fever
• Tularemia

Question 8

Genus of deer tick?

Answer 8

Ixodes

Question 9

What’s a quick trick to determine if tick is a deer tick (Ixodes scapularis)?

Answer 9

look for black legs/feet

Question 10

Causative organism of Lyme (in North America)?

Answer 10

Borrelia bergdorferi, a spirochete

Question 11

Name this Season 3 winning queen.

Answer 11

Raja!

Question 12

Sources of false positive and false negatives Lyme tests

Answer 12

Lyme is a clinical diagnosis

False Negatives

• negative in early disease
• early antibiotic persistent negativity
• post antibiotic relapse may be seronegative

False positives

• cross reacts with other spirochetes
• positive from past exposures
• sera with high titer of autoantibodies

All that is seropositive is not Lyme Disease