Cases of Lyme Disease Soar in Region
A Jump in Cases
Wednesday, April 8, 2009; Page B01
The black-legged tick nymphs that have caused Lyme disease reports in the Washington region to soar will emerge with the spring flowers this month, and one thing is certain: They are hungry.
The most recent statistics show that Lyme disease reports more than doubled in Virginia and Maryland from 2006 to 2007, the last year for which data are available. They have nearly doubled in the District, tripled in Howard County and quadrupled in Montgomery County. Loudoun County recorded half of all cases in Virginia.
"The black-legged tick is really coming down and taking hold in the Potomac region," said David Goodfriend, the Loudoun County health director. "There are a great many more ticks in the area than there were a number of years ago."
Goodfriend has had to become an expert on the disease, which takes its name from the town in Connecticut where a cluster of cases was first recognized in 1975. Since then, the disease has grown more prevalent along the East Coast, spreading south and west from Connecticut, with a number of mid-Atlantic states reporting an exponential growth in cases as the ticks rapidly multiply.
The ticks that carry the disease, which can result in heart and joint problems as well as Bell's palsy if not caught early, have been commonly called deer ticks because deer are the vehicles that are the Johnny Appleseeds in spreading the disease. But the unseen culprit in delivering the disease to humans is the white-footed mouse or another of his rodent friends.
The ticks need just three meals in their normal two-year life cycle. As larvae, they get their first feeding on the backs of rodents, which are disease carriers. The larvae grow into infected nymphs that drop off the rodent in the woods or someone's back yard.
"There they will crawl up on a piece of grass and wait until an animal brushes up against them, and the cycle continues," said Paul Mead, an epidemiologist with the federal Centers for Disease Control and Prevention.
That cycle continues with meal number two on that animal. And the nymph, which is the size of a pencil point, is much less likely to be noticed if it is feeding on, and infecting, a human.
If that nymph gets its meal and grows into an adult tick, it would like to hop onto a deer next.
"The adult ticks prefer to feed on deer, which are immune to the disease," Mead said. "Deer are the adult mating bars for black-legged ticks. That's where they like to meet their mates, and then they drop off to lay their eggs."
The spread of infected ticks in the Washington region has been dramatic as more farmland has been developed and deer have become ever more common roaming through back yards and parks.
"What used to be an occasional case now has come to be commonplace," said Karen Kingry, a pediatrician who treats children at Nighttime Care facilities in Montgomery, Howard and Anne Arundel counties. "For example, when we see a single swollen, not very painful, knee, it's almost always going to be Lyme disease."