Review
http://www.medpagetoday.com/InfectiousDisease/PublicHealth/tb/1320
BOSTON, July 7-Once upon a time, a kid who strolled through the woods to Granny's house risked ending up as a wolf's breakfast. Nowadays, her biggest threat would be likely to come from a creature hardly bigger than the period at the end of this sentence.
Lyme disease, transmitted to people by the minuscule deer tick, is the most common tick-borne disease in the America, according to the CDC.
More than 157,000 cases of Lyme disease have been reported in the U.S. since 1982, when the agency first began looking for it systematically. That translates into an overall incidence of about seven cases per 100,000 population, but many cases go unreported. In 2002, nearly 24,000 new cases of Lyme disease were reported, according to CDC records.
There's also evidence that the disease is spreading.
"We're seeing Lyme disease being reported from areas that haven't had Lyme disease before," says Linden T. Hu, M.D., an associate professor of medicine in the division of geographic medicine and infectious diseases at Tufts-New England Medical Center here. "In Massachusetts, we're seeing it spreading out to western Massachusetts, where the incidence has been very low up until three or four years ago, and we're seeing cases, lots of cases now reported from New Hampshire and Maine, which had very few cases reported three to five years ago."
According to Bela Matyas, M.D., medical director of the epidemiology program for the Massachusetts Department of Public Health, "Some of the increase in reported numbers has reflected improved reporting and diagnosis by healthcare providers, but at least some of it does appear to reflect geographic changes in the areas of risk."
Although Lyme disease was first diagnosed in people who lived in or near the town of East Lyme, Conn., cases have been reported in every state but Hawaii. They tend to be clustered in the northeast, upper Midwest, and Pacific regions.
One reason that the disease spreads so readily is that the ticks are tiny and frustratingly difficult to spot. A half-dozen of the larvae could just about dance on the head of a pin, and at nymphal stage, when they're most likely to transmit infection, they're about an eighth of an inch in length.
Summer is high season for Lyme disease, because ticks are most active, and their targets -- people -- are most likely to be outdoors, gardening, golfing, or just gamboling through the grass.
The ticks like to hang out in damp, shaded environments, such as woods and wetlands, and they especially like areas where there is leaf debris and low-lying vegetation, such as the edge of woods or the rough of a golf course.
When ticks sense the presence of a passing bare arm or ankle, they'll latch on for dear life. The bite of a deer tick is usually painless, but the consequences of that bite are anything but. If the tick manages to go undetected for at least 36 hours, it may transmit to its human host the causative bacterium Borellia burgdorferi.
Experts recommend avoiding areas of tick infestation. When that's unavoidable, wearing light-colored clothing makes it easier to spot ticks, and long-sleeved shirts and pants tucked into socks or shoes may keep ticks from reaching skin. Insect repellants with DEET can also help to keep the pests from latching on.
The CDC recommends the following method for removing embedded ticks: "Embedded ticks should be removed using fine-tipped tweezers. DO NOT use petroleum jelly, a hot match, nail polish, or other products. Grasp the tick firmly and as closely to the skin as possible. With a steady motion, pull the tick's body away from the skin. The tick's mouthparts may remain in the skin, but do not be alarmed. The bacteria that cause Lyme disease are contained in the tick's midgut or salivary glands. Cleanse the area with an antiseptic."
If a person does become infected, the first symptom is often -- but not always -- erythema migrans, or the classic diagnostic "bull's-eye" rash. It is characterized by an erythematous center surrounded by a clear zone which itself is often surrounded by a larger erythematous area. This can occur anywhere from three to 30 days after a bite. Other symptoms are nonspecific, and may include fever, fatigue, malaise, headache, myalgia, and arthralgia.
If left untreated, the infection can advance to affect the central nervous system, causing facial nerve palsies or other cranial neuropathies, or lymphocytic meningitis. Musculoskeletal complications can include migratory joint and muscles pain with or without clinical signs of swelling. Cardiac complications are uncommon, but may include myocarditis or transient atrioventricular block.
| 
