Taking a bite out of Lyme disease

Nursing, Apr 2003 by Pauldine, Elizabeth Fell

Learn how to identify and treat Lyme disease and how to help your patients avoid infection.

LYME DISEASE, a multisystem disorder caused by the spirochete Borrelia burgdorferi, is the most common tick-borne disease in the United States. If not treated early, it can cause severe arthritic, neurologic, and cardiovascular syndromes. However, 20% to 40% of those infected don't develop the classic sign of Lyme disease, a bull's-eye rash called erythema migrans, so early diagnosis is a challenge.

This article will help you identify patients with Lyme disease and other tick-borne illnesses (see Picking Off Other Tick-borne Diseases). I'll also discuss how to treat patients with Lyme disease and what to teach them to minimize future infection risks.

Fast facts about Lyme disease

Three major risk factors for contracting Lyme disease are activity location (spending time outdoors), geography (living or working in areas where the disease is endemic), and the season the patient is bitten by a tick (May through September).

In the West (California and Oregon), the western blacklegged tick carries B. burgdorferi. In the upper Midwest (Wisconsin and Minnesota) and the Northeast (from Maine to Maryland), the black-legged tick, also known as the deer tick, carries B. burgdorferi. Most cases occur in these geographic areas. Both of these ticks are smaller than common dog and cattle ticks. In their larval and nymphal stages, they're no bigger than a pinhead.

Ticks become infected with B. burgdorferi after feeding on deer or white-footed mice infected with the spirochete. A tick is unlikely to transmit B. burgdorferi to a person if it's been attached to his skin for less than 36 hours. The longer it's been attached, the higher the likelihood of disease transmission.

Staging Lyme disease

If your patient has Lyme disease, his condition may fit into one of three stages: early localized, early disseminated, and late persistent (see Staging Lyme Disease). However, not all infected patients experience every stage.

In the early localized stage, 60% to 80% of patients exhibit erythema migrans 7 to 14 days following a tick bite. To be considered a sign of Lyme disease, the rash must be at least 2 inches (5 cm) in diameter, although the average rash is 6 1/2 inches (16.25 cm).

In many cases, manifestations of the early disseminated stage resolve without treatment, but antibiotic therapy reduces the likelihood of long-term complications, such as permanent heart block.

Some patients develop signs and symptoms of the late persistent stage without previously experiencing earlier disease features. About 60% of untreated patients develop arthritis. Although it typically dissipates after months with treatment, arthritis may become chronic.

A small percentage of patients continue to have persistent, disabling problems, such as joint and muscle pain, and fatigue, despite treatment for Lyme disease. Late neurologic manifestations may appear years after the initial infection.

Diagnosing Lyme disease

The health care provider will base diagnosis on the patients history, signs and symptoms, lab findings (if applicable), and risk factors. All cases of Lyme disease, which average 15,000 annually, must be reported to the Centers for Disease Control and Prevention.

Serologic testing using an

enzyme-linked immunosorbent assay (ELISA) test or an indirect fluorescent antibody (IFA) test can help confirm a diagnosis in certain patients. Because of the high likelihood of false-negative results in the first 4 weeks after the tick bite, serologic testing is recommended for patients 8 weeks after being bitten by a black-legged tick and for patients suspected of having early disseminated or late persistent disease. A Western blot analysis is indicated if results from the first test (ELISA or IFA) are indeterminate or positive.

Antibodies can remain for months or years after infection and treatment, so seroreaction alone doesn't indicate active disease. Neither positive serologic test results nor a history of Lyme disease ensures that a person has protective immunity.

Treating Lyme disease

The first step to preventing and treating Lyme disease or any tickborne disease is to remove the tick (see Removing the Culprit). Medication isn't typically indicated for tick bites. However, because a dose of doxycycline (200 mg for an adult) given within 72 hours after a bite from an infected deer tick can prevent Lyme disease from developing, a patient should receive treatment before serologic test results are available if he meets the following criteria:

He lives in a region where ticks carrying Lyme disease are endemic.

A deer tick has been attached for more than 24 hours.

He has erythema migrans.

A 14- to 21-day course of oral doxycycline or amoxicillin is recommended for patients with a tick bite history, a rash (or history of a rash) resembling erythema migrans, or arthritis. Antibiotic therapy provides symptom relief and prevents disease progression. Intravenous antibiotics are indicated to treat refractory signs and symptoms, such as arthritis, nervous system disease, heart block, and manifestations of late persistent disease.