Lyme Disease

Description

Lyme disease is caused by infection with Borrelia spirochaetes (B. burgdorferi, B. afzelii and B. garinii). The organisms are transmitted through the bite of ticks of the Ixodes ricinus complex in the United States, Europe and Asia. After an incubation period of several days, the spirochaetes disseminate haematogenously to multiple organs.

Symptoms

A history of environmental exposure (such as camping in an endemic area) is significant. Flu-like symptoms often accompany the rash. Common symptoms of systemic disease include headache, fatigue, chills and arthralgias. Neck stiffness or photophobia may reflect meningitis. Common ocular symptoms include blurred or double vision, pain and photophobia.

Signs

Lyme disease is renowned for its protean clinical manifestations. Its progression is described in 3 stages, although all may coexist.

• Stage 1: a pathognomonic, localised skin rash (Erythema migrans) develops. Erythema migrans consists of single large erythematous skin lesion, often with a pale or indurated centre (“bull’s-eye”), that may expand over several days. Conjunctivitis or periorbital edema may occur.
• Stage 2 reflects organ dissemination: the skin, joints, heart, and central nervous system are most commonly involved. Possible ocular signs are listed below.
• Stage 3 appears in 60 percent of untreated patients after months to years, typically with a large joint oligoarticular arthritis. Chronic encephalopathy and neuropathy are observed occasionally.

On ocular examination, a red eye may reflect conjunctivitis or episcleritis. Reduced acuity, impaired colour vision, and relative afferent pupillary defect vision occur with optic neuritis. Keratitis produces corneal clouding and vascularisation. There may be anterior or posterior uveitis: Iritis may manifest ciliary injection and aqueous cells or flare; Posterior uveitis or retinitis may show vitreous flare, opacities or discolouration. elevation of the retina with retinal detachment; and disc swelling with optic neuritis.

Prevalence

Varies geographically. Around 15,000 cases are reported in the Unites States each year.

Significance

Potentially life- and vision-threatening. Optic neuritis may cause blindness, particularly in children.

Differential Diagnosis

Syphilis, rickettsial infections, rheumatoid arthritis.

See Also

Conjunctivitis, Iritis, Choroiditis, Optic Neuritis, Retinal Detachment.

Management

Blood tests

Diagnosis is based on a history of exposure, symptoms, signs and blood tests. Enzyme-lined immunosorbent assay (ELISA), measures the binding of serum antibodies to Borrelia antigen. Positive or equivocal cases are confirmed with Western blot. Polymerase chain reaction (PCR) testing can also be used to monitor treatment. Of note, patients with Lyme disease have been misdiagnosed with syphilis, since they often produce a false-positive titre of flourescent treponemal antibody, absorbed (FTA-ABS).

Additional tests

Thorough neurological examination is required to exclude central or peripheral neurological involvement. Electrocardiogram (ECG) abnormalities may be present.

Oral and Topical Medication

Treated patients generally have an excellent prognosis. Early disease is treated with doxycycline, 100mg twice daily (or amoxycillin 500mg three times daily) for 2 to 3 weeks. Resistant cases, or those with organ involvement, are treated with an intravenous cephalosporin or penicillin for 2 to 4 weeks and observed for several hours after commencement of therapy for a transient immunological reaction. Topical corticosteroids are administered for anterior segment inflammation. Patients are reviewed regularly until disease resolution.

Prevention

A vaccine is available as a course of 3 injections, with boosters required every 1 to 3 years. Prevention includes minimizing exposure to ticks, barrier protection and insect repellents. Ticks found on the body are best removed with tweezers applied to the head and mouth parts