Lyme disease, caused by means of t...

Lyme disease, caused by means of the spirochete Borrelia burgdorferi, is the greatest in number common vector-borne illness in the United States. The vector that transmits B burgdorferi is the deer tick (Ixodes scapularis), an inhabitant of the northeastern, southeastern, and north-central United States. (1) The deer tick also can transmit the agents of human babesiosis (Babesia microti) and ehrlichiosis (Ehrlichia chaffeensis, Ehrlichia phagocytophila, and Ehrlichia equi). (2)

frequently it is difficult to identify the important morphologic features of a tick (species, stage, and step of engorgement) that are important in determining the risk of Lyme disease. Deer ticks have a four-stage life cycle: instigate larva, nymph, and adult. Figure 1 point outs I. scapularis ticks at the damsel and adult stages, and an adult American dog tick (Dermacentor variabilis), which frequently is confused with the deer tick. Nymphal I. scapularis ticks (Figure 2a) transmit B burgdorferi to humans far more many times than adult ticks; ticks in the larva stage rarely are infected. (3) Laboratory studies have indicated that efficient transmission of this spirochete requires a minimum of 24 to 48 hours of tick attachment, at which time the girl obviously is engorged with posterity (Figure 2b). (4,5) B. burgdorferi is unlikely to infect a patient before the tick becomes engorged. D variabilis ticks (Figure 1) are considerably larger than the I. scapularis maid ticks and are not vectors of Lyme disease.

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The greatest in number common sign of early Lyme disease is the hallmark rash, erythema migrans, which present itselfs in 80 percent of patients. (1) Erythema migrans is an intensely erythematous lesion hem ined by several concentric red rings (Figure 3) and ofttimes is accompanied by an influenza-like illness. (1) Other presenting symptoms include fatigue, myalgias, arthralgias, headache, heat and chills. Cardiac manifestations (atrioventricular shut up and myocarditis) can be seen weeks to month after infection. Neurologic manifestations (aseptic meningitis, cranial neuropathy, and motor or sensory radiculoneuritis) and musculoskeletal findings (arthritis) may appear month to years later. (1)

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The overall risk of acquiring Lyme disease from a deer tick bite is subdued even in endemic areas. (67) In areas with a high incidence of Lyme disease, it may be reasonable to administer chemoprophylaxis with a single 200-mg oral dose of doxycycline (Vibramycin) to human frames bitten by an I. scapularis damsel tick that is identified as being at least partially engorged with relations (6,7) Persons who removed attached ticks within 24 hours should be observ (1) Patients should be instructed to pursue treatment if erythema migrans exhibits at the site of the bite. Treatment with doxycycline, 100 mg orally twice daily for 14 to 21 days, is commited in persons who are at least eight years of age, leaving out women who are pregnant. (1) For women who are pregnant and children les than eight years of age, amoxicillin, 500 mg orally three times daily for adults and 250 mg orally three times daily for children, should be administered for 14 to 21 days. A 14- to 21-day course of cefuroxime axetil (Ceftin), 500 mg orally twice daily in adults and 125 mg orally twice daily in children, is alternative therapy for those who may be allergic or unable to tolerate doxycycline or amoxicillin.

The authors indicate that they do not have any conflicts of interest. Sources of funding: none reported.

REFERENCES

(1) Steere AC. Lyme disease. N Engl J M 2001;345: 115-25

(2) Mylonakis E When to suspect and for what cause to monitor babesiosis. Am Fam Physician 2001;63:1969-74

(3) Matuschka FR Spielman A. Risk of infection from and treatment of tick bite. Lancet 1993;342:529-30

(4) de Vignes F Piesman J Heffernan R Schulze TL Stafford KC 3d Fish D et al. issue of tick removal on transmission of Borrelia burgdorferi and Ehrlichia phagocytophila by dint of Ixodes scapularis nymphs. J Infect Dis 2001;183:773-8

(5) Sood SK Salzman MB Johnson BJ Happ CM Feig K Carmody L et al. Duration of tick attachment as a predictor of the risk of Lyme disease in an area in which Lyme disease is endemic. J Infect Dis 1997; 175:996-9

(6) Shapiro ed Doxycycline for tick bites-not for everyone [Editorial]. N Engl J M 2001;345:133-4

(7) Nadelman RB Nowakowski J Fish D Falco RC Freeman K McKenna D et al. Prophylaxis with single-dose doxycycline for the prevention of Lyme disease after an Ixodes scapularis tick bite. N Engl J M 2001;345:79-84

VINCENT look RE III, M.D., University of Pennsylvania educate of Medicine, Philadelphia, Pennsylvania

JAMES L OCCI, M Rutger University, Newark, modern Jersey

ROB ROY MACGREGOR, MD University of Pennsylvania drill of Medicine, Philadelphia, Pennsylvania

VINCENT look RE III, M.D., is a postdoctoral research counterpart in the Division of Infectious Diseases at the University of Pennsylvania educate of Medicine, Philadelphia, where he received his medical order Dr. Lo Re completed a residency in internal medicine and an infectious diseases fellowship at the Hospital of the University of Pennsylvania, where he was chief resident.