Big bucks to battle a tiny, terrible tick


April 25, 1999|By Mike Burns

IF CARROLL County is spending $30,000 on something, it must be important. That's usually considered a big-ticket item by the county commissioners, unless it's a quick pay raise for themselves.

The money is earmarked to inoculate some 200 outdoors county workers for Lyme disease, the debilitating illness spread by infected deer ticks the size of a pinhead.

A series of three shots over 12 months costs $150 (an annual booster shot may also be required) but the potential costs of treatment and rehabilitation for someone infected can be substantial, justifying the prevention, county officials say.

This is the first year that an approved vaccine is available (though still not for children).

Even so, there's a 1-in-5 chance that the new vaccine won't prevent the disease because of genetic differences.

And Carroll workers in woods and grasslands this summer will not have the full protection of the new vaccine, since the series of shots takes a year.

More deer and mice

The blood-borne disease (named for the Connecticut town where it was discovered 24 years ago) has been spreading throughout the Northeast (and upper Midwest) as the populations of wild deer and mice (both favored hosts of the tick) have mushroomed.

More than 100,000 cases of Lyme have been recorded by the federal Centers for Disease Control and Prevention since 1982.

Last year, Maryland recorded 500 diagnosed cases of Lyme disease ; a decade earlier, only 12.

While the symptoms -- nausea, fatigue, headache and joint pains -- may be common to many human ailments, physicians in the Northeast are increasingly homing in on Lyme disease as a possible cause.

Indeed, several studies show that doctors have prescribed antibiotics for many patients who did not eventually test positive for the disease. In one study of Eastern Shore patients, two-thirds of the patients getting prescriptions for Lyme did not have the disease; a similar study by Yale University scientists found the same result.

One reason is that prompt treatment with antibiotics is the most effective way to treat the infection, whose only visible sign is a small red bull's-eye around the skin where the tick dug in. Delaying treatment can allow the bacterial illness to attack the nervous system and heart and cause arthritis.

A series of laboratory blood tests is often used to diagnose the illness. A new, one-hour test for Lyme came on the market this year. But actual field studies will determine just how accurate it will be.

This year may be worse

This year is expected to bring an even more serious spread of the disease, scientists predict. Warmer weather, larger deer herds and greater human encroachment on animal habitat will all play a role.

Blame the acorn

But mostly blame it on the acorns. Especially the acorn bumper crop of 1997.

An explosion of acorns from oak trees occurs every four years or so, a long-standing pattern of species survival for the tree against the forest animals who eat or squirrel away most of the acorns, preventing them from growing into future oaks. A mature tree may typically drop 1,000 acorns a year; the fourth year, it will drop 50,000 acorns to increase its chances of reproduction.

But that means more food for white-footed mice, whose population soars. In turn, that abundance of mice attracts lots of young ticks -- who bite and pass on the Lyme disease bacteria to mice, or acquire the bacteria from infected mice and transmit it to other mice and deer.

The disease continues to circulate between insect and mammal -- and to any humans who come in contact with infected ticks in the woods, or even in unmowed grass.

Two years after a large fall acorn crop, the number of tick larvae may be eight times as large as a normal year, researchers report. And the number of ticks on each mouse rises by 40 percent.

Borrelia burgdorferi

The war against the deer tick (and its insidious bacterium, Borrelia burgdorferi) is being fought by scientists on different fronts. With 16,000 reported U.S. cases a year, including many who may initially pass off the symptoms as simply flu, the struggle is escalating.

Medical researchers are looking for a vaccine that would cause an allergic reaction where an infected tick bites a human, so the infection would be easily noticed and promptly treated.

Biologists are testing fungus and microscopic earthworms as natural killers of deer ticks. Poisons that kill other insects are under study. Vaccines for mice (to break the cycle) are also being explored.

The vaccine is a welcome weapon. But it doesn't provide long-term immunity.

Carroll parks and road employees must still rely on careful daily body checks for hidden ticks. The insect must feed for 48 hours to transmit the bacterium.

Mike Burns is The Sun's editorial writer in Carroll County.

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