Properties

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment & Prevention

Borrelia burgdorferi

Flexible, motile spirochete.

Visualized by dark field microscopy, Giemsa’s & silver stains.

Route cultures from patient usually negative.

Transmission:

- animal reservoir: deer, rodents.

- transmitted by bite of hard ticks.

- tick must feed for 24-48 hrs to transmit infectious dose – inspecting skin after exposure can prevent disease.

Spread of organism from bite site through surrounding skin, followed by dissemination via the blood to various organs – heart, joints & CNS.

Disease: Lyme disease

Stage 1:

- erythema chronicum migrans (ECM)

- rash begins at site of bite, then spreads out in a ring.

- spreading circular red rash with a clear center at bite site.

- accompanied by flu-like symptoms such as fever, chills, fatigue & headache.

- secondary skin lesions.

- arthralgias.

Stage 2:

- occurs weeks to months later.

- cardiac & neurologic involvement.

- myocarditis or pericarditis.

- accompanied by various forms of heart block.

- acute aseptic meningitis.

- cranial neuropathies, e.g. Bell’s palsy & peripheral neuropathies.

Stage 3:

- arthritis of the larger joints.

- chronic progressive CNS disease.

Serologic diagnosis:

- detect IgM antibody.

- rising titer of IgG antibody with ELISA.

- indirect immunofluorscence test.

Positive test should be confirmed with a Western blot analysis.

Patients treated early in the disease may not develop detectable antibodies.

PCR test to detect organism’s DNA.

Stage 1:

- doxycycline

- amoxicillin

Late-stage disease:

- penicillin G

- ceftriaxone

Borrelia recurrentis & Borrelia hermsii

Transmission:

- B.recurrentis: human body louse.

- B.hermsii: soft ticks

- main reservoir: rodents & other small animals.

Relapsing nature of infections is caused by antigenic variation.

Mortality up to 40% for louse-borne type.

Disease: relapsing fever.

Symptoms:

- fever

- chills

- headaches

- multiple-organ dysfunction

Diagnosis made by seeing large spirochetes in stained smears of peripheral blood.

Giemsa stain is used.

Tetracycline, e.g. doxycycline beneficial early in illness & may prevent relapses.