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Tick-borne Lyme disease increasing, record number of cases expected.


Maryland health authorities counted 82 cases of Lyme disease across the state through July of this year, and a University of Maryland entomologist believes the final count will eventually top last year's record 238 cases.

"We have every reason to expect 1991 will have more cases than 1990," said Nancy L. Breisch, a UM extension entomologist. "We suspect that the [deer] tick itself is increasing," and also that there will be better reporting and better diagnosis of the illness by doctors.

Lyme disease is transmitted by the deer tick. But the federal Centers for Disease Control is now investigating reports that another common tick species - the Lone Star tick - is also capable of transmitting the illness.

The total number of Lyme disease cases reported in Maryland last year jumped 72 percent from the year before, from 138 to 238 cases statewide. Only 55 cases were reported in 1988, before it became mandatory for physicians to report cases to the local health department.

More than 8,000 cases of Lyme disease nationwide were reported last year to the CDC. Sixty percent of the 3,873 cases reported this year through July were in the mid-Atlantic states.

"So we really are in the thick of things here," Breisch said.

Early symptoms include a "bull's-eye" rash around the site of the tick bite, fatigue, a stiff neck and flu-like symptoms.

If left untreated, the disease can affect the victims' joints, liver, eyes, kidneys and spleen.

The target of the new CDC research, the Lone Star tick, is found from eastern Texas, Oklahoma, Kansas and Missouri to the Atlantic coast, at least as far north as southern New Jersey and Pennsylvania.

"We have lots of Lone Star ticks in Maryland," said Breisch. "I've had more Lone Star ticks sent to me this year for identification from human bites than in the last two years combined."

But so far, she said, "There's been no confirmed reports of Lyme disease being transmitted by the Lone Star tick in the state of Maryland."

A 1989 tick survey found that less than 20 percent of Maryland's deer ticks carried the Lyme disease bacterium. None of the Lone Star ticks carried it, Breisch said.

The adult Lone Star tick is known scientifically as Amblyomma americanum.(cq) It is most easily identified by the single, pearly-white spot on its otherwise brown back, Breisch said.

The Lone Star tick came under scrutiny after an outbreak of 200 Lyme disease cases in southeastern Missouri, where the deer tick - Ixodes dammini - is unknown. One family physician there reported that some of his Lyme disease patients brought him the ticks that bit them, and they were identified as Lone Star ticks.

Breisch said CDC researchers have found spirochete bacteria in some Lone Star ticks that resemble the Lyme disease bacteria. But they have been unable to get the organism to grow so that it can be positively identified.

Health authorities in Texas also have isolated a bacterium from Lone Star ticks that looks like Lyme disease. But Breisch said the researchers were unable to infect mice with it.

Mice are the primary reservoir for the bacteria, without which they cannot exist. The ticks merely transmit the illness from mice to people.

If the bacteria found in the Lone Star tick won't infect mice, that raises doubts about whether they are really Lyme disease type, or some variant of it, or represent an unidentified organism.

"It may well turn out that Amblyomma can transmit Lyme disease," Breisch said. "But that doesn't change anything as far as what people need to do to avoid Lyme disease."

Efforts to control the deer tick, which transmits the disease to humans, are considered impractical, so "it's public awareness and personal protection that's going to eventually lower cases of Lyme disease," Breisch said.

* First, stay away from infested areas or, if you must be there, wear long pants and sleeves, tuck your pant legs into your socks or boots. Tick repellent such as Duranon is effective in warding off the pest.

* Check yourself for ticks twice daily, especially at bedtime or while bathing. Remove any you find and send them to the Cooperative Extension Service for identification.

"Note the date of the tick attachment so that if you do develop symptoms, you can bring it to the attention of the physician," Breisch said. After identification by a series of blood tests, Lyme disease is readily treated with antibiotics.

People generally contract the disease from June through August, when the deer tick nymphs are most active, and people are most likely to venture into the woods and fields where the ticks live.

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