8. Lyme Disease Flashcards
What is this a picture of? What is it classic for?
Classic target lesion of ECM (erythema chronicum migrans). Classic for Lyme disease
Lyme disease: what are symptoms? what is the causative spirochete? carried by what animal?
Begins with characteristic expanding skin lesion, ECM, followed by neurologic, cardiac or joint abnormalities.
The caustive spirochete is Borrelia burgdorferi, carried by deer ticks.
Lyme dz: epidemiology?
What geographic areas?
What months of the year?
Geography:
- Northeast (MA to Georgia)
- Midwest, Wisconsin, Minnesota
- CA/Oregon
Peak occurs in June and July (when tick nymphs feed on animals and humans)
Lyme: what are the preferred animal hosts for the larval and nymphal stages of the deer tick? preferred host for the adult stage?
Larval/nymphal: white footed mouse (reservoir)
Adult: white tailed deer (not reservoir, does not get sick)
How long does the tick have to remain on the person to transmit Lyme?
24 h before transmitting spirochete. has to become engorged with blood.
Sx of early Lyme?
ECM (target rash) around site of tick bite.
Bacteremia with fever, chills, malaise, fatigue, arthralgia.
ECM lesions usually fade after 3-4 weeks even if untreated.
Sx of late Lyme disease?
Disseminated -> secondary annular skin lesions in half of patients, diffuse erythroderma or urticaria.
Neuro involvement in 20%, including aseptic meningitis, Bells palsy, peripheral neuropathy
(incidentally, my aunt had Late Lyme - she got numbness and tingling over one whole arm. Took about 5 docs at DHMC to figure out what was going on).
May have cardiac involvement.
May also have arthritis (another card)
If Late Lyme presents with arthritis in a patient, what will the arthritis look like?
Transitory/migratory in joints, tendons, bursa, muscle, bone.
Lasts only hours to days in a given location.
May have longer-lasting true arthritis in a few joints.
These lesions are classic for what stage of Lyme dz?
How would you describe?
Late Lyme (Stage II). Secondary annular lesions, resemble the primary target lesion, but smaller and migrate less.
what are sx of Chronic Lyme dz (Stage III)?
these sx will evolve over what time frame?
evolve over 6-12 m.
Sx: -chronic arthritis in a few large joints
- acrodermatitis chronica atrophicans
- subacute endephalopathy
- peripheral neuropathy
what kind of tick is this? what characteristics tell you that it is the kind that carries Lyme?
Deer tick (larva on right, nymph on left, adult in center)
black legs and smooth-edged body shell
the NYMPH is the one that transmits dz
what is this a pic of?
engorged deer tick
has to be engorged to transmit dz
what is this a pic of?
Spirochetes from the gut of a deer tick.
This is what causes Lyme dz
Why would spirochetes cause relapsing/remitting disease?
Stealthy organism: once your body makes antibodies to its outer lipoproteins, it can create a new lipoprotein coat
In Stage II (Late) Lyme dz, what % of patients get arthritis?
60% get transitory arthritis
Lyme disease tends to present in the same few months that viral meningitis is prevalent. How to tell them apart? (think about fever, duration of illness, CSF contents)
Lyme:
afebrile, Illness > 7 d, CSF has < 10% polys, ECM, may have cranial palsy, papilledema
Viral meningitis:
febrile, lasts < 3d, CSF has 50% polys
Why is a dx for Lyme disease so tricky?
- tick bite recalled in only 30% of cases
- only 50% present with classic ECM rash
- cultures may not yield orgs
- ELISA for the spirochete has delayed reacivity
- PCR may give false negatives
what is the best diagnostic test for Lyme?
serologic testing for immune response via ELISA.
- but immune response may be delayed -> neg result
- if pt was treated with abx, may not develop antibodies
- frequent false positives and cross-reactivity
what test can help back up ELISA results?
Western blot for evidence of the spirochete. must be positive for 5 of possible 10 bands.
The bottom line. Does Early Lyme require testing for dx? what about Late Lyme?
Early: in a patient with classic ECM, from an area with endemic Lyme, does not require lab confirmation
Late: requires objective evidence of clinical dz + lab evidence of infection (ELISA, serology). Symptoms would include Bell’s palsy, arthritis, aseptic meningitis, heart block
Lyme: treatment.
what stage is treatment most effective?
Treatment for acute?
treatment for chronic?
Most effective if initiated during Early (stage I)
Acute: abx such as doxycycline.
Chronic: 4 week course of oral abx (doxy), or parenteral course of ceftriaxone. Less effective.
Prevention of Lyme disease?
Control of deer/mice in endemic areas
tick removal (make sure to get the whole thing) within 24h
Long pants, insect repellent, wash clothes with repellent.
differential Ddx of Lyme?
babesiosis
Erlichiosis
anaplasmosis
rocky mountain spotted fever
tularemia
It’s important to not order Lyme serology too early: why?
It will be negative for a while even after the pt has gotten Lyme.
