Chapter 3Infectious Diseases Related To Travel

Jeffrey R. Miller, Paul S. Mead

INFECTIOUS AGENT

Lyme borreliosis (Lyme disease) is caused by spirochetes belonging to the Borrelia burgdorferi sensu lato complex, including B. afzelii, B. burgdorferi sensu stricto, and B. garinii.

MODE OF TRANSMISSION

Lyme disease is transmitted through the bite of nymph and adult Ixodes ticks, which are found in temperate forested and woodland areas of North America and Eurasia. Adult and nymphal Ixodes ticks are tiny, roughly the size of sesame seed and poppy seed, respectively; infected people are often unaware that they have been bitten.

EPIDEMIOLOGY

In Europe, Lyme disease occurs from southern Scandinavia into the northern Mediterranean countries of Italy, Spain, and Greece. Incidence is highest in central and Eastern European countries, such as Slovenia, where the annual reported incidence is 155 cases per 100,000 population. In North America, highly endemic areas are the northeastern and north-central United States. Transmission has not been documented in the tropics.

Lyme disease is rarely reported in returning travelers. All ages are at risk for infection during travel to endemic areas. Infection is associated with exposure to tick habitats (such as wooded, brushy, or grassy areas).

CLINICAL PRESENTATION

Incubation period is 3–32 days. Approximately 80% of people infected with B. burgdorferi develop a characteristic rash, erythema migrans (EM), within 30 days of exposure. EM is a red, expanding rash, with or without central clearing, that is often accompanied by symptoms of fatigue, fever, headache, mild stiff neck, arthralgia, or myalgia. A rash <5 cm in diameter that develops while the tick is still attached or within 48 hours of tick bite is likely caused by a hypersensitivity reaction and is not an indication of infection.

Within days or weeks, infection can spread to other parts of the body, causing more serious neurologic conditions (meningitis, radiculopathy, and facial palsy) or cardiac abnormalities (myocarditis with atrioventricular heart block). Untreated, infection can progress over a period of months to cause monoarticular or oligoarticular arthritis, peripheral neuropathy, or encephalopathy. Long-term sequelae can be typically observed over a number of months, ranging from 1 week to a few years.

The clinical presentation of Lyme disease in Eurasia is generally similar to the presentation of infection in North America. Multiple EM rashes have been described more often in patients infected in North America than in Europe. Patients infected in Europe may be more likely to develop neuroborreliosis or the rare skin manifestations, acrodermatitis chronic atrophicans and borrelial lymphocytoma.

DIAGNOSIS

Observation of an EM rash with a history of recent travel to an endemic area (with or without history of tick bite) is sufficient to make a diagnosis of Lyme disease. Serologic testing is often negative in the first few weeks of illness and should not delay treatment in patients with a recent onset (2–3 weeks) of a characteristic EM rash. For patients with evidence of disseminated infection (musculoskeletal, neurologic, or cardiac manifestations) 2-tiered serologic testing, consisting of an ELISA/IFA and confirmatory Western blot, is recommended. Patients suspected of acquiring Lyme disease overseas should be tested by using a C6-based ELISA, as other serologic tests may not detect infection with European species of Borrelia.

TREATMENT

Guidelines for treatment of Lyme disease have been published by the Infectious Diseases Society of America and are available at http://cid.oxfordjournals.org/content/43/9/1089.full. Depending on the stage of disease, most patients can be treated with either oral doxycycline or intravenous ceftriaxone. Physicians unfamiliar with Lyme disease may wish to consult an infectious disease specialist for further guidance. Additional information about Lyme disease can be found on the CDC website (www.cdc.gov/lyme/).

PREVENTIVE MEASURES FOR TRAVELERS

No vaccine is available. Measures to prevent Lyme disease and other tickborne infections include avoiding tick habitats, using insect repellent on exposed skin and clothing, and carefully checking every day for attached ticks (see Chapter 2, Protection against Mosquitoes, Ticks, and Other Insects and Arthropods). Remove ticks by grasping them firmly with tweezers as close to the skin as possible and lifting gently. Avoid crushing the tick’s body. Do not use petroleum jelly, a hot match, nail polish, or other products to remove a tick. Postexposure prophylaxis is generally not recommended unless the traveler sustained a tick bite in a highly endemic area. Prophylactic antibiotics are not recommended for travelers.

BIBLIOGRAPHY

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