infections
Lyme Disease
Introduction
Lyme disease is a tick-transmitted infection caused byBorreliaspecies, primarily byBorrelia burgdorferiand sometimes byBorrelia mayoniiin the United States. These spiral-shaped bacteria are called spirochetes (see figure). Most people are infected when they go outdoors in wooded areas where Lyme disease is common and are bitten by ticks infected with the bacteriaBorreliaspecies. Typically, a large, red spot appears at the site of the bite and slowly enlarges, often surrounded by several red rings. Untreated, Lyme disease can cause fever, muscle aches, swollen joints, abnormalities of the electrical conduction system of the heart, and eventually problems related to brain and nerve malfunction. The diagnosis is based on the typical rash and symptoms, opportunity for exposure to ticks, and blood tests to detect antibodies to the bacteria. Taking antibiotics usually cures the disease, but some symptoms, such as joint pain, may persist. (See also Overview of Bacteria .) Lyme disease was recognized and named in 1976 when a cluster of cases occurred in Lyme, Connecticut. It is now the most common tick-borne infection in the United States. It occurs in 49 states. More than 90% of the cases occur along the northeastern coast from Maine to Virginia and in Wisconsin, Minnesota, and Michigan. On the West Coast, most cases occur in northern California and Oregon. Lyme disease also occurs in Europe, China, Japan, and the former Soviet Union. Usually, people get Lyme disease only if a tick remains attached to them for at least a day and a half. Usually, people get Lyme disease in the summer and early fall. Children and young adults who live in wooded areas are most often infected. The bacteria that cause Lyme disease are transmitted by the deer tickIxodes, so named because the adult ticks often feed on the blood of deer. Young deer ticks (larvae and nymphs) feed on the blood of rodents, particularly the white-footed mouse, which is a carrier of Lyme disease bacteria in the United States. Ticks are usually in the nymph stage when they infect people. Deer do not carry or transmit Lyme disease bacteria. They are only a source of blood for adult ticks. In Europe, larger mammals such as sheep are hosts for the adult tick. Lyme disease is the most common tick-borne infection in the United States. Deer do not carry or transmit Lyme disease bacteria and are only a source of blood for adult ticks. Deer ticks also carry other infections (such as Babesiosis and The bacteria that cause Lyme disease are transmitted to people when an infected tick bites and stays attached for more than 36 hours. Brief periods of attachment rarely transmit disease. At first, the bacteria multiply at the site of the tick bite. After 3 to 32 days, the bacteria migrate from the site of the bite into the surrounding skin, causing a rash called erythema migrans. The bacteria may enter the lymphatic system and infect lymph nodes. Or the bacteria may enter the bloodstream and spread to other organs, such as the skin in other areas of the body and the heart, nervous system, and joints. 