Introduction
“Borrelia burgdorferi is a parasite transmitted by infected ticks from deer, mice, and other small rodents that harbor the spirochete”(1). These animals can have huge numbers of the bacteria and not show any symptoms of disease. Yet when these same spirochetes are transmitted to humans, they cause problems in many organ systems.Lyme disease is a tick-borne inflammatory disorder caused by a spirochete, B. burgdorferi. Its clinical hallmark is an early expanding skin lesion, erythema migrans (1), which may be followed weeks to months later by neurologic, cardiac, or joint abnormalities. The B. burgdorferi spirochete causes most Lyme disease in the United States. All stages of Lyme disease may respond to antibiotics, but treatment of early disease is the most successful. “Lyme arthritis” was recognized in November 1975 as the result of an unusual geographic cluster of children with inflammatory arthropathy in the region of Lyme, Connecticut (1). Its early elucidation—natural history (1), immunopathogenesis (2), epidemiology (2, 3), pathology(2), and therapy (3) was carried out primarily at Yale University by Steere, Malawista, and their colleagues. It soon became clear that this was a multisystem disorder (Lyme disease) (2,3) occurring at any age,in both sexes, and often preceded by a characteristic expanding skin lesion, erythema chronicum migrans (2). In 1982, B.b (2) isolated the spirochete that bears his name from Ixodes scapularis ticks collected on Shelter Island, New York, and linked it serologically to patients with Lyme disease. During almost three decades of study, much has been learned about the etiology, pathogenesis, clinical spectrum, and treatment of Lyme disease, but many questions remain unanswered, particularly those related to how the spirochete sometimes avoids immune recognition, and regarding the pathogenesis of chronically persistent symptoms experienced by some patients.
EPIDEMIOLOGY
Lyme disease is widespread in temperate climates of the northern hemisphere in the U.S. and across Europe and Asia(3). Although it has been reported in 49 of 50 states, there are three distinct foci (4): the Northeast from southern Maine to Maryland, the upper Midwest, and the West in Northern California. Of more than 15,000 new cases currently being reported each year, more than 90% come from only 10 states, 8 northeastern and mid-Atlantic and 2 north-central: New York, Connecticut, Pennsylvania, New Jersey, Wisconsin, Rhode Island, Maryland, Massachusetts,Minnesota, and Delaware (4). The ratio of unreported to reported cases has been estimated at 7 to 12:1. Lyme disease accounts for more than 95% of U.S. vector-borne infectious diseases. The primary vectors are tiny,hard-bodied ticks of the Ixodes ricinus complex: major foci of disease correspond to the distribution of I. scapularis(5).
PATHOGENESIS
Lyme disease behaves like a rheumatic disorder (2) because the generally rather unaggressive, causative organism, B.burgdorferi, is both powerful antigenically and apparently able periodically to gain access to immunologically privileged sites (i.e., to hide in tissue). Initially, disease develops after inoculation of skin with B. burgdorferi from an infected tick, leading to the herald skin lesion, EM. In addition to EM, B. burgdorferi causes another early skin lesion, benign lymphocytoma (3), and a late one, acrodermatitis chronica atrophicans (3), both of which are seen primarily in Europe.
SIGN AND SYMPTOMS
Early symptoms of infection include nonspecific, virus-like symptoms, such as headache, fever, fatigue, and joint aches. A classic sign is a circular rash of characteristic appearance known as erythema migrans.

DIAGNOSIS Lyme disease is diagnosed clinically based on symptoms, objective physical findings (such as erythema migrans, facial palsy or arthritis) or a history of possible exposure to infected ticks, as well as serological blood tests(1,2,3,4,5). The EM rash is not always a bullseye, i.e., it can be red all the way across. The most widely used tests are serologies, which measure levels of specific antibodies in a patient's blood. The serological laboratory tests most widely available and employed are the Western blot and ELISA. A two-tiered protocol is recommended by the Centers for Disease Control and Prevention (CDC): the sensitive ELISA test is performed first, and if it is positive or equivocal, then the more specific Western blot is run.
TREATMENT
Antibiotics are the primary treatment for Lyme disease; the most appropriate antibiotic treatment depends upon the patient and the stage of the disease(4). According to the Infectious Diseases Society of America (IDSA) guidelines, the antibiotics of choice are doxycycline (in adults), amoxicillin (in children), erythromycin (for pregnant women) and ceftriaxone, with treatment lasting 10 to 28 days.Alternative choices are cefuroxime and cefotaxime(5). prevention Protective clothing includes a hat, long-sleeved shirts and long trousers tucked into socks or boots(3). Light-colored clothing makes the tick more easily visible before it attaches itself.People should use special care in handling and allowing outdoor pets inside homes because they can bring ticks into the house(4).