Lyme Disease

Lyme disease is a multisystem infection caused by the bite of a tick infected with the spirochete Borrelia burgdorferi. Systemic dissemination can occur within days to weeks. The symptoms tend to occur in stages, somewhat arbitrarily divided into early localized, early disseminated, and late. Prompt diagnosis is crucial because early treatment is highly effective, whereas late disease is more difficult to eradicate. In addition to the symptoms and signs, the history of possible exposure to ticks is extremely important, as there is a history of tick bite in less than 30% of cases. In patients with later manifestations of Lyme disease, there may be a history of earlier manifestations (e.g., in a patient presenting with seventh nerve palsy, history of prior rash should be solicited).

Causes

Lyme disease is caused by an infection from a micro-organism, itself transmitted by a bite from the wood tick, a blood-sucking parasite which normally lives on deer. The wood tick is found in many areas, particularly in forests where deer are common. A tick will settle anywhere on a human body, but prefers warm, moist and dark places like the crotch.

When the tick has found a suitable place on the body, it sticks in its probe to draw up blood, exposing the host to the risk of infection.

Symptoms

Early localized disease

• Rash: solitary erythema migrans (EM, see below), which may be pruritic, painful, or neither ++++
• Flulike symptoms: fatigue, headache, fever, stiff neck

Early disseminated disease (may occur in various combinations)

• Rash: multiple EM
• Flulike illness with fevers, chills, fatigue
• Neurologic: facial weakness or paralysis, headache and stiff neck, painful or weak limb, dysesthesias
• Cardiac (more common in males): palpitation, dyspnea, syncope, chest pain
• Musculoskeletal: arthralgias, pain over muscles, tendons, and bursae
• Ocular (resulting from conjunctivitis, iritis, or keratitis): red eye, eye pain, blurred vision

Signs

Early localized disease

• EM: large (median size, 15 cm), red, usually flat, round, or oval eruption at the site of tick bite. Rash morphology can be variable. It is typically located at skin creases or thorax and appears 1 to 33 days after exposure, typically between 7 and 10 days.

Early disseminated disease

• Fever with or without rash
• Cutaneous: multiple. EM (secondary lesions are usually smaller and lack the central punctum)
• Neurologic: most commonly facial nerve palsy, which can be bilateral
• Cardiac: irregular pulse, cardiac rub or gallop
• Ocular: conjunctival injection, corneal fluorescein uptake from keratitis, cells in the anterior chamber; rarely, disc edema and retinal changes from vasculitis or inflammation
• Musculoskeletal: frank synovitis occasionally found in this stage
• GI: rarely, hepatomegaly or splenomegaly

Treatment

Treatment of early localized Lyme disease typically involves a course of the oral antibiotics doxycycline or amoxicillin administered for 3 to 4 weeks.

Medicines used against Lyme disease include:

• Oral doxycycline, amoxicillin or cephalosporin antibiotics are the usual first choices.
• When antibiotics by injection are being given, then benzylpenicillin (eg Crystapen) and ceftriaxone (Rocephin) are the usual choices.
• No particular choice and method is superior to another - the decision is made by the infectious disease specialist and is dependent on the individual circumstances.