Image Gallery An adult female deer tick (Ixodes scapularis) perched on a vine tendril, enlarged about seven times.

The Lowdown on Lyme Disease

By Barbara Pleasant

Tick-borne Lyme disease continues to expand across North America while the search advances for better ways to cope with this emerging disease. In the future, a human vaccine, a fungus that lives in leaf mold, pesticide-dispensing deer feeders and mice "wicks" all promise better defenses against Lyme disease. For now, "dressing like a geek" when you're in the woods or fields, keeping tick-eating guinea fowl and other poultry, and encouraging wild-animal diversity to better control tick populations naturally are the safest, most effective tick-control strategies on hand.

THESE TICKS ARE TINY

For 25 years before 1977, when Lyme disease was first traced to tiny tick nymphs the size of poppy seeds, people in Old Lyme, Connecticut, and many other places, had been getting sick. Often their aches and lack of energy were diagnosed in error as chronic fatigue syndrome, lupus or even multiple sclerosis. Now, we know most had Lyme disease, which is caused by the Borrelia burgdorferi bacterium and spread via tiny ticks hitching rides on birds, dogs, deer, mice and other critters.

Today, Lyme disease is concentrated in the Northeast, but it has been identified in every comer of the United States and in some parts of Canada. In 2002, statistics from the Centers for Disease Control and Prevention (CDC) confirmed more than 23,000 new human Lyme disease cases spread over 47 states. Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island and Wisconsin accounted for 95 percent of those cases. Leaders of private sector efforts to study and stop Lyme disease say even more cases would be confirmed if the official criteria were broadened. In Canada, infected ticks now are prevalent in parts of Ontario bordering on Lake Erie and in several forested sections of British Columbia.

Although people can get Lyme disease at any age, children younger than 15 and adults aged 45 to 59 are at greatest risk for becoming infected, according to CDC statistics.

Lyme disease is one of several bacterial infections transmitted by ticks. In the eastern and upper midwestern United States, it is transmitted most often by the black-legged tick (Ixodes scapularis), commonly called the deer tick. West of the Rockies, the western black-legged tick (I. pacificus) carries the disease. And lone star ticks (Amblyomma americanum) can transmit two other Lyme-like diseases with similar symptoms. Ticks are most likely to transmit Lyme disease to humans when they are nymphs only slightly bigger than the period at the end of this sentence. When they are engorged with blood, nymphal Lyme disease-causing ticks expand to the size of a small pinhead. When fully grown, these ticks still are very small —not much bigger than a sesame seed.