| • | main reservoir = rodents (the hosts of larva and nymphs) |
| • | deer may play a role in feeding adult ticks |
| • | concurrent infection with other tick-transmitted agents, such as Babesia or Ehrlichia, has been described |
Erythema Chronicum Migrans
| • | more than half have extra-cutaneous signs and symptoms (joints, nervous system, heart) |
| • | risk of infection is low if tick is attached for less than 24hrs |
| • | the annular lesions develop within 3 months of tick bite |
| • | lesions are multiple in 25% of cases (results from hematogenous dissemination of the organism) |
| • | histology: superficial and deep perivascular and interstitial |
| • | lymphocytes, sometimes with abundant plasma cells and eosinophils |
| • | diagnosis requires an index of suspicion based on clinical features |
diagnosis:
| • | serology – IgM response begins 2 to 4 weeks after onset of erythema migrans |
| • | highest culture yield is skin biopsy of e. migrans at periphery of lesion |
Borrelial Lymphocytoma
| • | classically a solitary bluish red nodule with predilection for ear lobe, nipple/areola region, or scrotum (especially in a child) |
| • | histology: dense dermal lymphocytic infiltrate, dominated by polyclonal B-cells; often germinal centers |
Acrodermatitis Chronica Atrophicans
| • | vector = Ixodes ricinus (mostly in Europe) |
| • | rarity in US is due to the rarity of B. burgdorferi subtype VS461 |
| • | occurs 6 months to 10 years after untreated e. migrans |
| • | usually starts unilateral on the extensor aspect of one extremity |
diagnosis:
| • | almost 100% seropositive, usually very high serum IgG titers |
| • | culture biopsy to confirm diagnosis (ACA is a cutaneous example of prolonged survival of B. burgdorferi). |
| • | prophylaxis: single 200mg dose within 72 hours of tick removal can prevent Lyme disease |
| • | treatment: 100mg BID x 14 to 21 days is effective against each of the "big three" |
| • | Lyme disease above dose is used to treat "early" Lyme disease (i.e. eythrema chronicum migrans) (if < 8 years old, then amoxicillin 500mg PO tid X 14 to 21 days) |
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