Lyme disease
Though it has probably been in existence for a long time, Lyme disease was only recently identified as a distinct illness. The disease is caused by the spirochete Borrelia burgdorferi, a corkscrew-shaped microorganism whichis spread by ticks that thrive in wooded areas and tall grasses and infect deer, mice, and domestic animals as well as humans. Most common in New England,the upper Midwest, and northern California, it has been diagnosed in more than 40 states. Although Lyme disease is not fatal, it can cause lasting debilitation.
A Lyme disease infection progresses through three stages. The first stage includes a bull's-eye-like rash that can appear at the site of the tick bite ina few days to a few weeks. There can also be symptoms similar to influenza, headaches, and soreness in the neck. The second stage includes irregular heartbeat, joint pains, disturbances of vision and memory, and facial-nerveparalysis. The disease can then progress to a third stage which includes joint inflammation and arthritis. While it can be easily treated with antibiotics, especially oral tetracycline, in the early stages, Lyme disease is often misdiagnosed until it has progressed to the second or third stage, during which the damage can become permanent. Antibiotics are also being developed for chronic Lyme disease which is characterized by chronic or intermittent symptoms.
The disease was first reported in Lyme, Connecticut, in 1974 by rheumatologist Allen Steere (1943-), who noticed that certain patients were exhibiting a distinct set of symptoms that could not be attributed to other known illnesses. Symptoms resembling those of Lyme disease had been reported in parts of Europe since the turn of the century, but clinicians were not sure whether the European syndrome had a similar origin to Lyme disease.
Then, in 1981, a survey of microorganisms in ticks revealed that a tick-bornespirochete was responsible for both the European and American syndromes. Because many people in the United States and Europe contract the disease withoutapparent exposure to the tick, many experts believe that mosquitoes, bitingflies, and birds may also spread the organism.
Despite a full understanding of the disease, researchers have been developinga vaccine. At Yale University, scientists isolated the gene in the Lyme disease spirochete that leads to the production of the protein OspA, a protein common to many bacteria. Using genetic engineering, the researchers induced another bacterium to produce large quantities of OspA. When they injectedlaboratory mice with the protein and exposed the mice to the Lyme disease organism, none of them developed the disease. Furthermore, antibodies could beextracted from the mice and injected into uninfected mice, affording them protection from the disease as well.
While vaccines are undergoing testing in humans, scientists have recently discovered the DNA sequence for the causative agent, Borrelia burgdorferi. This advance will help researchers develop new diagnostic tests and vaccines, as well as determine individual susceptibility to chronic symptoms. Untilthen, education and proper early diagnosis appear to be the best means to control the disease. Experts advise campers and hikers to cover exposed skin, especially on the legs, when walking in the woods or tall grasses. People should also check themselves and their children thoroughly for ticks (particularlydeer ticks roughly the size of a pinhead), and gently remove any ticks theyfind with tweezers to insure that the mouthparts of the tick are not left inthe bite. Because the Lyme disease spirochete resides in the midguts of ticks, crushing the ticks could inject the contents of the midgut into the bite wound.
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