Lyme disease prevention and treatment.
The Infectious Diseases Society of America recently updated its guidelines on identification and management of Lyme disease and other zoonoses associated with bites from Ixodes ticks.
Ixodes scapularis ticks can carry and transmit the organisms responsible for causing Lyme disease, human granulocytic anaplasmosis (HGA), and babesiosis.
Lyme disease is caused by infection with the spirochete Borrelia burgdorferi; it is the most common tick-associated infection in North America and is endemic in the Northeast, the upper Midwest, and Northern California. There have been no proven locally acquired cases of Lyme disease south of Maryland.
HGA, caused by a Rickettsia species that infects neutrophils, has a geographic distribution like that of Lyme disease. The clinical illness--fever, chills, headache, myalgia, leukopenia, thrombocytopenia, and elevated liver enzymes--is much more common in adults than in children.
Babesia, a genus of intraerythrocytic protozoa, causes an illness similar to malaria. Babesia microti are endemic in coastal southern New England, New York, New Jersey, Wisconsin, and Minnesota; other pathogenic Babesia species are found in California, Washington, and Missouri.
Bites from the Lone Star tick in the southern United States have been associated with an erythema migrans-like lesion; this southern tick-associated rash illness, abbreviated as STARI, is not thought to be caused by Borrelia infection.
The best way to prevent tick-borne infections is to avoid tick bites by wearing protective clothing, using insect repellent containing DEET, and checking frequently for ticks; if found, they should be removed quickly.
Skin disinfection alone is recommended if removal of an embedded tick leaves residual mouthparts in the skin; complete removal does not reduce the risk of developing Lyme disease.
An erythematous skin lesion that develops while the tick is still attached (or within 48 hours of removal) is most likely a tick-bite hypersensitivity reaction. These are typically smaller than 5 cm in diameter and should improve within 48 hours.
Routine antimicrobial prophylaxis or serology for Lyme disease is not recommended after tick bites. However, single-dose doxycycline prophylaxis may be considered when an engorged I. scapularis tick (in a Lyme disease-endemic area) is removed after attachment for 36 hours or longer and the prophylaxis can be administered within 72 hours of tick removal.
Protective immunity should not be presumed following a previous case of mild Lyme disease or prior administration of the recombinant Lyme disease vaccine, which is no longer available.
Persons who reside in endemic areas should seek medical attention promptly if they develop a rash or viral-type illness up to 1 month following tick removal.
The clinical features of erythema migrans--an expanding ovoid erythematous lesion greater than 5 cm in diameter that develops 7-14 days after a tick is detached--are sufficient to make a clinical diagnosis of early Lyme disease. But clinical features alone are not sufficient to diagnose extracutaneous Lyme, HGA, or babesiosis. If there is uncertainty about the diagnosis, the CDC recommends two-stage testing of acute and convalescent sera for Lyme disease.
Oral doxycycline, amoxicillin, or cefuroxime are recommended for adults with early Lyme disease without specific neurologic syndromes or high-grade atrioventricular block. Macrolides are recommended only in cases where the first-line agents cannot be used. The same antibiotics are recommended for the treatment of late Lyme arthritis.
Ceftriaxone is recommended for early Lyme disease only if the patient has advanced atrioventricular block, meningitis, or radiculopathy. Patients with symptomatic myopericarditis or advanced heart block associated with Lyme disease should be hospitalized and monitored, and temporary cardiac pacing may be required until the atrioventricular block resolves. Late neurologic Lyme disease should also be treated with ceftriaxone.
Coinfection with HGA or babesiosis should be considered when a patient has more severe initial symptoms or does not improve as expected with appropriate initial antibiotic therapy, and the patient lives or has traveled in geographic areas where these infectious agents are endemic.
Acute and convalescent sera are the most sensitive tests for the diagnosis of HGA. Doxycycline is recommended for treatment, which should be initiated without waiting for serology results. If fever persists for more than 48 hours after initiation of antibiotics, an alternative diagnosis or coinfection with babesia should be considered.
Thin blood smear examination for parasites and babesia DNA polymerase chain reaction are the best tests for babesiosis in symptomatic patients. Acute and convalescent sera may be used to confirm the diagnosis. Antimalarials (atovaquone plus azithromycin, or clindamycin plus quinine) are used for the treatment of babesiosis. Patients with severe cases may require partial or complete RBC exchange transfusion.
Wormser, Gary P., et al. The Clinical Assessment, Treatment, and Prevention of Lyme Disease, Human Granulocytic Anaplasmosis, and Babesiosis: Clinical Practice Guidelines by the Infectious Diseases Society of America. Clin. Infect. Dis. 2006;43;1089-134.
DR. GOLDEN (right) is professor of medicine and public health and DR. HOPKINS is associate director of the medicine/pediatrics residency program at the University of Arkansas, Little Rock. Write to Dr. Golden and Dr. Hopkins at our editorial offices or firstname.lastname@example.org.
BY WILLIAM E. GOLDEN, M.D., AND ROBERT H. HOPKINS, M.D.
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|Title Annotation:||THE EFFECTIVE PHYSICIAN|
|Author:||Golden, William E.; Hopkins, Robert H.|
|Publication:||Internal Medicine News|
|Date:||Dec 1, 2006|
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