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When the Tick Bites

by Mary Jasch

Got achy joints? One reason could be Lyme Disease, caused by Borrelia burgdorferi, courtesy of the deer tick. “Lyme disease is the most prevalent vector-borne disease in the U.S.," says Dr. Greg Tsongalis, director of molecular pathology at Dartmouth Medical Center in Massachusetts. The bacteria don't like oxygen, so they gather in hidden places like joints, connective tissue, stomach lining, and the brain.

The accepted method for testing human blood for Lyme Disease is a two-tier structure. ELISA, the basic screening test run on a machine, is an antibody test that looks for our body's response to the bacterium. Test results may differ depending on which agent a lab uses to attract the antibodies. The Western Blot, a labor-intensive hand-done test, is used to confirm a positive ELISA test.

In the ELISA test, technicians look for an antigen/antibody reaction. Some researchers have found that false negatives occur if the antibodies are tied up on the disease organism and none are available to attach to the testing agent. The test can be negative although the person is ill.

False positives can occur with an arthritic factor. “Some people with arthritis will bind up with the machine test," says one technician who asked to remain anonymous. “Then we do the Western Blot¯, the “Gold Standard" Lyme Disease test. Although it's not 100% accurate, it's the accepted best method out there.

“If someone is not feeling well and the test comes up negative, either do it again or do it somewhere else. There are a number of different tests available based on antibodies used for ELISA. If they're not using the same antibody, it's very unlikely to get two false negatives or positives. Be persistent and request re-testing," Tsongalis explains.
“I think it's almost just as important to screen everybody with the Western Blot to make sure there are no false negatives, but it's cost prohibitive to a person and insurance doesn't cover it."
“The performance characteristics of Lyme Disease tests are less than desirable by our traditional standards for lab testing."

Physicians are becoming aware of looking for Lyme Disease symptoms during certain times of year. But there are many diseases that can cause the same symptoms ¬ other tick-borne or none. With Lyme Disease, symptoms show up within a week or so ¬ aches, grogginess and arthritis are chronic effects. “The problem is the symptoms are not unique to the disease. There's really no specific symptom that can pinpoint a disease. Lyme Disease is under-diagnosed but a difficult thing to differentiate,"¯ says Tsongalis.

Whether or not joint fluid is tested depends on symptoms and the length of infection. A “joint tap"¯ test has limitations. Tsongalis believes that taking preventive antibiotics can create more problems than the threat of Lyme Disease can. “We have to be more cautionary. It's going to end up giving us more problems than the help we'd get from that and breed resistant organisms if they're not taken appropriately," he says.

A lot of people have the misconception that they're going to get Lyme Disease by spending time outdoors, but only a small percentage of ticks carry the spirochete. "Even if a deer tick bites, it must be embedded for 20 to 30 hours. If it bites you and it falls off, you are not at risk. If it stays in, you are at risk," says Tsonglais.

Four Facts of Lyme Disease:
* The tick must be a female deer tick.
* A small percentage of them carry the spirochete.
* Getting bit doesn't mean you have Lyme Disease.
* If you feel achy and groggy, see a physician.

Cases in New Jersey in 2003:
* Babesiosis (deer tick): over 30
* Human Granulocytic Erlichiosis (deer tick): 7
* Human Monocytic Erlichiosis (dog or Lone Star tick): 2
* Lyme Disease (deer tick): 2,596

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published June 15, 2004

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