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Consumer Information Center New Vaccine Targets Lyme Disease

Consumer Information Center: New Vaccine Targets Lyme Disease
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New Vaccine Targets Lyme Disease

New Hope for Diminishing 'Great Masquerader'

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by Carol Lewis

Don Chinnici's hands hurt for months. He kept getting sore throats. When he turned his head to either side, it was painful to move it back. He suffered from a lack of concentration, memory loss, aching joints, and depression. Yet, the then 41-year-old New Jersey native just assumed it was all part of getting older.

But as symptoms worsened, Chinnici became concerned that he was suffering from far more than the effects of middle age. A diagnostic questionnaire and extensive testing eventually confirmed that Chinnici had Lyme disease.

Last December, the Food and Drug Administration licensed the first vaccine to help prevent Lyme disease, a bacterial infection transmitted by tick bites. LYMErix, distributed by SmithKline Beecham Pharmaceuticals, Philadelphia, is an unusual vaccine. Like most vaccines, it stimulates the human immune system to produce antibodies, in this case directed against Borrelia burgdorferi (B. burgdorferi), the bacteria that cause Lyme disease. But unlike typical antibodies that fight the bacteria in a person's body, animal experiments suggest that when a tick bites a vaccinated person, the vaccine-induced antibodies enter the tick and kill the bacteria there.

FDA emphasizes that the vaccine, however, is not 100 percent effective, and should not be considered a substitute for other standard preventive measures against infection, including wearing protective clothing, using tick repellent, and removing attached ticks (see accompanying articles).

"The vaccine's effectiveness depends on people receiving three doses over a one-year period," says Karen Elkins, Ph.D., an immunologist with FDA's Office of Vaccines, Research and Review. The initial dose is followed by a second dose one month later, and a third dose 12 months after the first.

The time of year the vaccination is given is important as well, Elkins stresses. Vaccine administration should be timed so that the second dose and the third dose are given several weeks before the beginning of the B. burgdorferi transmission season, usually April in the Northeastern United States.

FDA has approved the vaccine for people 15 to 70 years old who live or work in grassy or wooded areas, where infected ticks tend to thrive. But, although LYMErix may provide protection for most people, the vaccine does not prevent all cases of Lyme disease. It is also not known how long protection against Lyme disease lasts after vaccination.

The national Centers for Disease Control and Prevention says that people of all ages are susceptible to the infection, but that the highest reported rates of Lyme disease are in children 2 to 15 years old, and adults aged 30 to 55.

The Bite of a Tiny Tick

The most common carrier of Lyme disease in the United States is the deer tick (so named for its dependency on deer to reach the adult stage of its complex, two-year life cycle), or black-legged tick. The Western black-legged deer tick also transmits Lyme disease along the coasts of northern California, Oregon and Washington.

Ticks become infected with the Lyme disease bacteria when they feed on the blood of an infected animal--most notably, the white-footed mouse, white-tailed deer, other mammals, and birds--a method necessary for them to progress to each of three life-cycle stages.

According to CDC, ticks are usually in the nymph stage (between larva and adult) when they transmit Lyme disease to humans. Approximately the size of a poppy seed, the nymphs are most active between May and July. The spiral-shaped Lyme-causing bacterium, B. burgdorferi, enters the skin at the site of a bite and migrates until it penetrates the bloodstream. It usually takes at least 36 hours following a tick bite for the bacterium to be transmitted, so early removal of attached ticks is very important.

Although in theory Lyme disease could spread through blood transfusions or other contact with infected blood or urine, CDC says no such transmission has been documented. And there is no evidence that a person can get Lyme disease from the air, food or water, through sexual contact, or directly from wild or domestic animals.

While at least one definitive case of Lyme disease acquired by either a deerfly or horsefly was documented in The New England Journal of Medicine in 1990, CDC says that no convincing evidence exists that the disease can be transmitted by insects such as mosquitoes, flies or fleas.

In rare cases, CDC also says, Lyme disease acquired during pregnancy may lead to infection of the fetus, but the effects of such transmission on the fetus remain unclear.

Telltale Rash Not the Whole Story

Early-stage Lyme disease is usually marked by a telltale skin rash called erythema migrans, which appears three days to one month after the tick bites. It starts as a small red spot at the site of the bite. As it enlarges, the center of the rash may clear, resulting in a bull's-eye appearance. Common sites for the rash are the thigh, groin, trunk, and armpits. CDC estimates that 85 percent of people with Lyme disease get the characteristic rash.

The rash is often accompanied by flu-like symptoms, including fever, fatigue and muscular pain. Other early signs can include secondary skin lesions and facial paralysis.

Although early Lyme disease almost always responds to appropriate antibiotic therapy, if untreated or inadequately treated, the condition can progress weeks, months or years after the tick bite to late Lyme disease, which is characterized by distinctive arthritic, neurologic and cardiac problems.

Although a tick bite is an important clue for diagnosis, many people cannot recall having been bitten because the tick is so tiny and its bite is relatively painless. (The picture at right shows a normal size thumb with a deer tick nymph on it.) "I don't recall ever being bitten by a tick," says Chinnici. Therefore, NIH advises physicians to base their diagnosis not only on the history of a tick bite, but also the patient's symptoms and a thorough ruling out of other diseases that may have triggered those symptoms.

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The Importance of Proper Diagnosis

FDA's concern about the potential for misdiagnosing Lyme disease is based on results from commonly marketed blood tests used for detecting antibodies to the organism that causes infection. Antibodies in the patient's blood indicate that the body's immune system has detected invaders, but some tests cannot tell if those invaders are the Lyme disease bacteria. The test most often used to detect antibodies is called an enzyme-linked immunosorbent assay (ELISA) technique.

In addition, in February, FDA cleared a new blood test for Lyme disease that can be used in a doctor's office. PreVue B. burgdorferi Antibody Detection Assay, made by Chembio Diagnostic Systems, Medford, N.Y., is intended, like the ELISA test, to be used as the first step in testing people suspected of having Lyme disease. The PreVue test searches for antigens made by the B. burgdorferi bacterium that is responsible for the infection.

Unlike ELISA, which must be performed in a lab, PreVue provides results in one hour at the doctor's office. Understanding the limits of such testing, however, is important in diagnosing and treating the disease, says Sharon Hansen, Ph.D., a microbiologist with FDA's Center for Devices and Radiological Health. She advises that the tests be used only to support a clinical diagnosis of the disease, as in Chinnici's case, and not solely for making initial diagnostic or treatment decisions.

"In early diagnosis of Lyme disease these tests should not be used to rule in or rule out the infection," she advises, "especially in the absence of a rash." She explains that a positive test result does not conclusively indicate infection, and that people with active Lyme disease may get a negative result. She adds that when the ELISA test is positive, it must be followed and confirmed by a supplemental, second-step test known as the Western blot. The ability of Western blot to detect antibodies specific for B. burgdorferi, she concludes, reduces the number of false positives obtained with ELISA.

Like ELISA, positive results from PreVue also must be confirmed with a Western blot test done by a laboratory.

Treatment and Prevention

Most Lyme disease patients can be successfully treated with standard antibiotics. FDA approved Ceftin (cefuroxime axetil) Dec. 19, 1996, for the treatment of early Lyme disease. Recommended regimens of oral antibiotics can speed the healing of the rash, and can help prevent subsequent symptoms such as arthritis or neurological problems.

Hansen says that patients treated in the early stages with antibiotics usually recover rapidly and completely. Patients treated in later stages of the disease also may respond well to antibiotics, but in some cases, symptoms of persisting infection or inflammation may continue or recur, causing permanent damage.

"Lyme disease is a great masquerader," she says. "The bacteria may lay dormant and the symptoms disappear, but as the bacteria becomes active again, the symptoms will reappear." Hanson adds, "Even when the bacteria is eradicated from the body, the damage that has already been done may persist."

FDA, CDC, and the National Institutes of Health all agree that education is the most important part of Lyme disease prevention. Research has indicated that early removal of a tick can ward off much of the danger, but diagnosing the disease and treating infection remain difficult.

"I can't emphasize strongly enough the importance of finding a doctor who is experienced in recognizing this infection," adds Chinnici. "As in my case, where Lyme disease is concerned, time is of the essence."

Lyme History 101

The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, says a skin rash similar to that of Lyme disease was recognized in Europe and was described in medical literature dating back to the turn of the century. Researchers believe that the disease may have spread from Europe to the United States in the early 1900s. But it wasn't until the influx of suburban developments into rural areas where deer ticks are common, coupled with the exploding deer population, that the disease became prevalent, according to NIAID.

Lyme disease was first recognized in the United States in 1975 when a cluster of rheumatoid arthritis cases occurred in the town of Lyme, Conn. The victims were mostly children, and the outbreak began with rashes, headaches, and joint pains during the summer months--the height of tick season.

By 1994, 48 states and the District of Columbia had reported Lyme disease cases, although most were concentrated mainly in the coastal Northeast, the Mid-Atlantic states, Wisconsin and Minnesota, and northern California. Three years later, the national Centers for Disease Control and Prevention says, more cases of Lyme disease were reported than the combined total of cases reported for measles, mumps, rubella, whooping cough, cholera, tetanus, diphtheria, meningitis, and a host of other lesser known conditions.

But CDC also estimates that thousands of Lyme disease cases go undiagnosed, untreated and unreported, due in large part to the disease's uncanny ability to mimic other illnesses.

Preventing Infection

Most cases of Lyme disease occur in the spring and summer months when ticks in the nymph stage are feeding and people generally spend more time outdoors, often with more skin exposed. To minimize the risk of contracting Lyme disease, the national Centers for Disease Control and Prevention recommends the following precautions:

If you do find a tick, be sure to remove it correctly and dispose of it properly.

Protecting Fido and Kitty

Household pets can get Lyme disease, too. Typical symptoms in animals include joint soreness and lameness, fever, and loss of appetite.

Currently three Lyme disease vaccines are available for dogs--LymeVax, Galaxy Lyme, and Canine Recombinant Lyme. Larry Elskin with the U.S. Department of Agriculture's Center for Biologics says that healthy dogs can be vaccinated when they are 9 weeks or older. (There is no vaccine available for cats.)

The American dog tick, which is more commonly found on pets, is much larger than the deer tick and, the national Centers for Disease Control and Prevention says, is not known to carry Lyme disease. Checking pets for all types of ticks before letting them enter the home reduces the risk of infection for both pet and owner.

For More Information

For more information on Lyme disease, contact any of the following organizations:

National Centers for Disease Control and Prevention
Division of Vector-Borne Infectious Diseases
Box 2087
Fort Collins, CO 80522
(970) 221-6400

National Institutes of Health
Lyme Lines
National Institute of Allergy and Infectious Diseases
9000 Rockville Pike
Bethesda, MD 20891

American Lyme Disease Foundation, Inc.
Mill Pond Offices
293 Route 100
Somers, NY 10589
(914) 277-6970

Carol Lewis is a staff writer for FDA Consumer.

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