New evidence to relieve fears about Lyme disease
From the July-August ACP-ASIM Observer, copyright © 2002 by the American College of Physicians-American Society of Internal Medicine.
By Deborah Gesensway
Since 1977, when some children in Lyme, Conn., mysteriously got arthritis, people have feared the illness now called Lyme disease. However, anxiety about Lyme disease now outstrips the disease itself as a medical problem, experts say.
"People are freaked out by ticks and Lyme disease, but their fear is way out of proportion to their real health risk," explained Bennett Lorber, FACP, professor of medicine and chief of the infectious diseases section at Temple University in Philadelphia. "For every one truth" about Lyme disease, he said, "there are 100 misconceptions, myths and unfounded anxieties."
Just like patients, physicians can fall victim to Lyme disease hysteria. However, the growing body of evidence about Lyme disease should reassure doctors and patients alike. In the past two decades, scientists have described the pathogenesis of this now treatable disease and traced it to the bacterium Borrelia burgdorferi carried by deer ticks.
It is now well documented that Lyme disease is actually hard to transmit. Recent research demonstrated that only 3% of people who recognized a deer tick bite in an area with a high incidence of Lyme disease (Westchester County, N.Y.) actually developed it.
The latest study of Lyme disease, which was published in the July 12, 2001, New England Journal of Medicine (http://content.nejm.org/cgi/content/abstract/345/2/79), concluded that giving a patient bitten by a deer tick a single 200 mg dose of doxycycline could prevent Lyme disease entirely. If contracted, moreover, the disease can be easily treated—at least for the vast majority of people—by a single 14- to 21-day course of antibiotics.
So how can physicians get past the fears and myths to effectively diagnose and treat the disease? Experts say the key is to base testing and treatment decisions on the likelihood that a particular patient actually has the disease.
Determining likely cases
When patients complain of vague symptoms like fatigue and malaise, some physicians make the mistake of testing for Lyme disease, noted Janine Evans, MD, associate professor at Yale University School of Medicine in New Haven, Conn., and co-editor of ACP-ASIM's "Lyme Disease" book. But the fact is the disease gets transmitted only in a limited geographic region, by one type of tick, primarily at certain times of the year.
Most Lyme cases have appeared in the Northeast and Mid-Atlantic states. According to the CDC, 92% of Lyme disease cases reported in 1999 came from Connecticut, Delaware, Maryland, Massachusetts, New Jersey, New York, Pennsylvania, Rhode Island and Wisconsin. "Even in an endemic area, the diagnosis of Lyme disease is unlikely for those with vague symptoms," Dr. Evans said.
What if patients in an endemic area get a tick bite? Should doctors automatically offer a prophylactic dose of doxycycline? Although some physicians now do just that, Robert B. Nadelman, MD, advises them to use antibiotic prophylaxis sparingly. Dr. Nadelman is lead author of the New England Journal of Medicine article and professor of medicine in the division of infectious diseases at New York Medical College and Westchester Medical Center.
"Most tick bites don't result in Lyme disease," he said. Only the Ixodes scapularis or deer tick is known to carry the bacteria that causes Lyme disease—and transmission is associated almost exclusively with ticks in the nymphal stage. Nymphs are most active from May through July, which is when symptomatic patients are most likely to show up in your office complaining of fever, fatigue, headache and muscle and joint pain.
"Our prophylaxis approach is based largely on sorting out patients at higher risk," Dr. Nadelman explained. He asks patients to remove the suspect tick with fine-tipped tweezers and bring it in for identification.
In his study, he found that the only ticks that transmitted Lyme disease were nymphs that had been attached to a person, feeding, for 72 hours. No one in his study developed the disease who had been bitten by a larval or adult tick, or a tick that fed for only a day or two.
To the right of the postage stamp are an adult male (bottom) and female (top) deer tick, Ixodes scapularis. In the center are two nymphal stage deer ticks, which can transmit Lyme disease. To the left of the stamp are an adult male and female American dog tick, Demacentor varibalis, which do not carry Lyme disease, but are frequently mistaken for deer ticks. Scale is 1/16 inch. Photo by Jim Occi/Lyme Disease Network.
The long timeframe is due to how the bacteria live, explained Eugene Shapiro, MD, professor of pediatrics, epidemiology and investigative medicine at Yale University, and co-author of the Infectious Diseases Society of America's Lyme disease diagnosis and treatment guideline. Spirochetes live in a tick's gut, he explained. They must be activated and move up to the tick's salivary glands before they can be transmitted to a victim.
"If you can identify that the tick is a partially engorged nymphal-stage tick from an endemic area, prophylaxis would clearly be worthwhile," Dr. Shapiro said. "But you need a lot of expertise to know that."
What if you can't tell an engorged I. scapularis nymph from an adult, let alone from another type of tick, insect or even a speck of dirt? A study of specimens submitted to physicians in Westchester County, N.Y., for tick identification found that a quarter of all the creatures were not I. scapularis ticks at all. Most were dog ticks, beetles, crab lice or head lice.
Because identifying a tick can be useful in deciding whether to prescribe prophylactic antibiotics, the Westchester physicians recommended that doctors in endemic areas learn to identify deer ticks or seek assistance from someone trained in entomology. "It does take a little practice—and a good hand lens," said Dr. Nadelman. "You can also become very good at estimating how long a tick has been attached because they really swell up after they feed."
Instead of focusing on the tick, doctors can "wait for a rash," as Temple's Dr. Lorber recommends.
"We now know that nearly everybody who gets the disease gets the rash," he said. A "perfectly reasonable approach" is to ignore a tick bite and treat patients only if an erythema migrans rash appears.
People used to think that only half of those who developed Lyme disease got a rash first. But subsequent data suggest that to be a gross underestimate, Dr. Nadelman said. He estimates that about 90% of those who get Lyme disease get an erythema migrans rash seven to 21 days after being bitten, but patients—-and physicians—overlook rashes when they appear.
Erythema migrans can be quite large (up to 10 cm), long lasting (two to three weeks if left untreated) and distinctive (oval and expanding a little each day). However, this type of rash rarely breaks out in plain view on the hands or face. Instead, it occurs in hard-to-see places where ticks like to attach and feed, such as the groin, buttocks or backs of knees. Erythema migrans rashes do not itch or hurt, and can be confused with a fungal rash or poison ivy.
Moreover, erythema migrans rashes always go away spontaneously, even if untreated. And contrary to popular belief, they mostly lack a central clearing that makes them resemble a "bull's eye" or "target."
A study published in the March 19, 2002, Annals of Internal Medicine (www.annals.org/issues/v136n6/full/200203190-00005.html) found that only 9% of 118 patients with confirmed Lyme disease had rashes with a "central clearing." Half of these patients also reported low-grade fever, headache, neck stiffness, myalgia, arthralgia or fatigue, while three had facial palsy. Only a minority were seropositive for B. burgdorferi, the bacteria that causes Lyme disease.
Problems with testing
Since the rash is usually readily diagnosed and assays are falsely negative the first several weeks of infection, physicians should rarely order seriologic assays for patients with erythema migrans.
Experts now recommend that physicians treat patients as soon as they see erythema migrans and reserve blood tests for questionable cases or for patients with extra-cutaneous disease. For instance, Dr. Nadelman said he might order an enzyme-linked immunosorbent assay (ELISA) test for a patient who lives in an endemic area and has a swollen knee without an obvious etiology. "But I wouldn't test somebody whose only complaint is fatigue," he said.
"If you gave every Oklahoman an antibody test for Lyme disease, you could find that 20% appear to have the disease when none actually do," explained Yale's Dr. Shapiro. "If, on the other hand, a Westchester County, N.Y., patient has subacute arthritis and positive test results, Lyme disease is likely."
For more on the limitations of blood tests for B. burgdorferi antibodies, see "Avoiding common Lyme diagnosis pitfalls and errors," page 16.
Almost all infected patients with early Lyme disease can be completely cured by a two- to three-week course of antibiotics such as doxycycline or amoxicillin. Patients with arthritis symptoms may require four weeks of treatment. A fraction of those treated for Lyme disease develop persistent symptoms such as fatigue, joint aches and pains, concentration and sleep disturbance, and sometimes shooting and burning pains. Another New England Journal of Medicine study published in the July 12, 2001, issue (http://content.nejm.org/cgi/content/abstract/345/2/85) concluded that treating these patients with prolonged courses of IV and oral antibiotics was not effective.
This type of "chronic Lyme disease" is real, explained Yale's Dr. Evans, who co-authored the study. "But additional antibiotics don't seem to be helpful, and we need to redirect our thinking" away from assuming antibiotics will cure this population.
In addition, she said the term "chronic Lyme disease" is misleading because it suggests persistent infection, which does not appear to be true.
So what should physicians do about patients who have persistent symptoms or attribute every new ache and pain to Lyme disease? "Try to reassure them and help them get on with their lives," Dr. Lorber said, "and explain that giving antibiotics over a long period of time has its own dangers."
Experts also point out that there is much patients can do to prevent infection in the first place. First, they should wear long, light-colored clothing when going into wooded areas where infected deer ticks live. At bedtime during the summer, they should check themselves for ticks and remove any they find.
A vaccine for the illness was once available, but the manufacturer pulled it off the market in February because of poor sales (not safety concerns). Experts say that patients who received the Lyme disease vaccine in the past should be reminded that their immunity has likely worn off by now, so they must take precautions when entering tick-infested areas.
Deborah Gesensway is a freelance writer in Glenside, Pa.
The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP-ASIM.
Here's a look at the most common mistakes primary care physicians make when they suspect a patient has Lyme disease:
Testing before treatment. The Infectious Diseases Society of America's guidelines state that an erythema migrans rash alone is sufficient to diagnose Lyme disease. At that point doctors should prescribe a 14- to 21-day course of doxycycline or amoxicillin.
False negative tests are very common for blood tests ordered within a few weeks of a tick bite. Because the tests detect antibodies that take several weeks to develop, less than 40% of infected patients will test positive initially, noted Robert B. Nadelman, MD, professor of medicine in the division of infectious diseases at New York Medical College.
Testing to follow up on a course of antibiotic treatment is not necessary. Antibodies may be present for years after cure and their presence does not necessarily reflect persistent infection.
"I've seen dozens of completely asymptomatic patients who have been treated repeatedly because the doctor kept getting a positive blood test," said Bennett Lorber, FACP, professor of medicine and chief of the infectious diseases section at Philadelphia's Temple University. "My one piece of advice: No follow-up blood tests."
Failing to examine the patient's entire body. When physicians don't ask their patients to undress completely during a physical exam, they can miss detecting erythema migrans. The rash rarely occurs in an easy-to-spot place like the hands or face. Instead, it develops where ticks like to bite, such as the groin or buttocks.
"Every summer we see a number of patients who complain of aches, pains and fever, but deny having a rash. When they disrobe for an exam, we discover one or more rashes," Dr. Nadelman said. "Some of our patients have seen other physicians who missed the rash because they didn't look carefully for it."
Physicians should be particularly alert to summertime illnesses without nasal or respiratory symptoms. He advises physicians to ask such patients to undress completely, then examine them "head to toe."
Seeking a "bull's eye" or "target" rash. Most erythema migrans rashes in the United States (unlike in Europe) do not have a central clearing. Expansion is a key clue for recognizing erythema migrans. In cases where patients' rashes resemble erythema migrans but appeared suddenly, experts suggest outlining the periphery of the rash with a pen. If the rash is bigger the next day, or systemic symptoms develop, consider initiating treatment for Lyme disease.
Experts say that many Web sites devoted to Lyme disease contain medical misinformation that can feed, rather than relieve, patients' anxiety about Lyme disease. For accurate, helpful information, see the sites below:
ACP-ASIM offers Lyme disease information and helpful links at www.acponline.org/lyme/. It also offers comprehensive material in the books "Expert Guide to Infectious Diseases" and "Lyme Disease." To order, go to www.acponline.org/catalog/books.
CDC Division of Vector-Borne Infectious Diseases (www.cdc.gov/ncidod/dvbid/lyme/index.htm) provides the most reliable source of Lyme disease information online.
Infectious Diseases Society provides Lyme disease practice guidelines at www.journals.uchicago.edu/CID/journal/issues/v31nS1/
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