Summer Of Lyme Disease Danger

By Cynthia Sanz, Discover magazine

Adam Stettner racked his brains trying to figure out when it happened. Could it have been while he was out jogging in the park? Or when he wandered into the woods near the golf course to hunt down a stray ball? Stettner never felt a bite or saw a rash. But sometime during the summer of 1994, he was bitten by a tick infected with Borrelia burgdorferi, the bacterium that causes Lyme disease.

Over the next few months, the bacterium went to work, stealthily winding its way through his bloodstream and ultimately wreaking havoc with his nervous system. ``The first time I knew anything was wrong was In February 1995,'' Stettner says. ``I was walking down the hall at work and suddenly the whole office started moving. It was like somebody took my brain and put it in a blender.''

For the next three years, Stettner submitted to test after test -- blood chemistries, CT scans, MRIs, spinal taps, anything doctors could think of to find the cause of his dizziness, nausea, memory lapses and debilitating fatigue. Finally, down to 130 pounds from 160, he tested positive for Lyme disease.

``I wouldn't wish what happened to me on anybody,'' Stettner says, a 26-year-old Wall Street trader. ``I lost a part of my life I can never get back.''

The recent FDA approval of a new Lyme disease vaccine has raised hopes that stories like Stettner's may someday be relegated to medical history books. This year people who live or vacation in tick-infested areas can take a series of three Lyme immunization shots. But the good news is tempered by some disquieting facts. The vaccine is approved only for adults, and it is not fully protective. One out of five who receive the vaccine and are bitten by infected ticks will still contract Lyme disease.

Worse, vaccinated people might be tempted to let their guard down. And this, of all years, is not a time to take chances. Ecologist Richard Ostfeld, who has spent the better part of the decade figuring out the boom-and-bust cycles of the Lyme bacterium as it circulates among ticks, mice and deer, is convinced that the conditions for spreading the disease will he more dangerous this summer than ever before. ``If things go as predicted, eastern oak forests and surrounding areas will be teeming with infected ticks,'' he says.

Why? Chalk it up to the robust acorn count of 1997. Many other factors contributing to the risk of exposure to Lyme disease are familiar: human encroachment into forests, growing deer populations and recent warm winters that have allowed more ticks to survive. The new variable comes from untangling the web of relationships that link the tick life cycle, the feeding habits of mice and deer and the species survival instincts of oak trees. ``We call it the acorn connection,'' says Ostfeld, of the Institute of Ecosystem Studies in Millbrook, N.Y.

The story begins deep in oak forests where every few years, oak trees undergo a process called masting, when they produce a bumper crop of acorns. ``It's an evolved reproductive strategy,'' Ostfeld says. ``If they dribble out a few acorns every year, there is a risk that all the nuts will be eaten by squirrels and deer and all the other things that eat acorns. But if the oak trees produce an enormous bumper crop every three or four years, then some acorns will survive and become seedlings.

Ostfeld's analysis of this boom-and-bust cycle has led him to conclude that two years after oak trees have their mast years, the risk of getting Lyme disease in an oak forest goes up dramatically. Conversely, two years after a low acorn production year, the risk in oak forests is much lower. The timetable revolves around the reproductive cycles of ticks and white-footed mice, the prime reservoirs of the Lyme bacterium.

In a mast year, the bumper crop of acorns lures deer into the oak forest. The deer are generally carrying a full cargo of adult ticks. So the ticks, when done feeding, fall to the ground and lay the eggs that will hatch into tick larvae the following summer. ``Wherever the deer are in the fall,'' says Ostfeld, ``that's where the larval ticks will hatch the next summer.''

Meanwhile, white-footed mice are also enjoying the acorn boom. The mice, almost 100 percent of which are infected with Lyme from previous tick encounters, spend the autumn munching acorns and storing reserves to get them through the winter. By the time the tick larvae hatch that next August, the forest is crawling with mice, says Ostfeld. ``Ticks get it from mice, mice get it from ticks -- they pass it back and forth. Which came first, nobody knows,'' says Ostfeld.

What is clear, though, is that by the next June or July, two years after the mast year, there are a lot of one-year-old ticks, or nymphs, in oak forests, and they stand an excellent chance of being infected.

That's worrisome because nymphs pose the greatest danger to people. Nymphs feed during June and July, months when people tend to spend time outdoors; adult ticks feed in the fall. And unlike the adult tick, which is generally easy to spot and remove before it transmits bacteria into the blood, the nymph tick is so tiny (the size of a poppy seed) that it often escapes detection.

``Since 1994 was a really good acorn year,'' says Ostfeld, ``we predicted there would be lots of larvae and mice in 1995, and lots of infected nymphs in 1996. It came true: 1996 saw a substantially higher number of Lyme case in humans. In Connecticut, reported cases more than doubled, rising from 1,548 in 1995 to 3,104 in 1996.

Ostfeld hopes to use the acorn count each year to predict when and where nymph ticks are likely to feed two years later, offering people another weapon in their Lyme prevention arsenal.

''The main means of protecting ourselves is still going to be not putting ourselves at risk, and the way to do that is to figure out when the ticks are out and where they are. I envision what I call Smokey the Tick warning people about what parks are liable to be particularly risky for Lyme,'' Ostfeld says.

But despite their successes, researchers admit that Lyme is far from beaten. To maintain immunity people will probably need annual booster shots. That may prove too demanding for those unaccustomed to regular doctor visits. It's also possible, in theory, that some people with a specific genetic makeup could develop an adverse reaction, similar to arthritis, to the antibodies the vaccine arouses.

Even with these concerns, researchers generally agree that the vaccine is a major advance for people living in places where there are lots of infected ticks.

THWARTING TICKS

Because the new Lyme vaccine is not 100 percent effective, the best defense against the disease remains a good offense. Avoid woody, overgrown or grassy areas. And if you're hiking, stay on the trail, Tuck your pants into your socks and wear light-colored clothing to make ticks visible. Spraying your pants and shoes with an insect repellent containing DEET helps, too. Avoid spraying face and hands, because DEET is toxic. Daily tick checks are a must. Nymphal ticks are tiny, and they like moist areas, so look in spots like the groin, navel, and behind the knees.