Identifying, Treating Lyme Disease in Primary Care

Geographic spread of the ticks that most often cause Lyme disease in the United States and a rise in incidence of bites, resulting in 476,000 new US cases a year, have increased the chances that physicians who have never encountered a patient with Lyme disease will see their first cases.

“It’s increasing in areas where it was not seen before,” Steven E. Schutzer, MD, with the Department of Medicine, Rutgers New Jersey Medical School, Newark, said in an interview. Dr Schutzer coauthored a report on diagnosing and treating Lyme disease with Patricia K. Coyle, MD, Department of Neurology, Renaissance School of Medicine at Stony Brook University, Stony Brook, New York.

The report, a Curbside Consult published in New England Journal of Medicine Evidence, comes amid high season for Lyme disease. Bites from an ixodid (hard shield) tick — almost always the source of the disease in the United States — are most common from April through October.

Identifying the Bite

About 70%-90% of the time, Lyme disease will be signaled by erythema migrans (EM) or lesion expanding from the tick bite site, the authors wrote. The “classic” presentation looks like a bullseye, but most of the time the skin will show a variation of that, the authors noted.

“The presence of EM is considered the best clinical diagnostic marker for Lyme disease,” they wrote.

Other dermatologic conditions, however, can complicate diagnosis: “EM mimickers include contact dermatitis, other arthropod bites, fixed drug eruptions, granuloma annulare, cellulitis, dermatophytosis, and systemic lupus erythematosus,” they wrote.

Testing Steps

“The current recommendation is to do two-step testing almost simultaneously,” Dr Schutzer said in an interview. The first, he said, is an ELISA (enzyme-linked immunosorbent assay)-type test and the second one, used for years, has been a pictorial view of a Western immunoblot showing which antigens of the Lyme bacteria, Borrelia burgdorferi, the antibodies are reacting to.

However, the pictorial view is subjective and some of the antigens could be cross-reactive. So the US Food and Drug Administration (FDA) “has been allowing newer substitutes like a second ELISA-like assay that often uses more recombinant, less cross-reactive antigen targets,” he said. The authors advised that, “The second-tier test should not be performed alone without the first tier.”

Dr Schutzer advised physicians to check with the lab they plan to use before sending samples.

“If you’re a practicing physician and you know you’re using a particular laboratory, you should familiarize yourself with them, talking to one of the clinical pathologists involved in advance to know what the limitations are.” Take the time to talk with the person overseeing the test and get tips on how they want the sample transported and how the cases should be reported, he said.

If the patient has neurological symptoms, he said, before treating talk with a neurologist who can advise whether, for instance, a spinal tap is in order or whether an emergency department visit is appropriate.

“If you just start proceeding you may mess up the diagnostic signs that could show up in a lab test. Don’t be hesitant to ask for extra input from colleagues,” Dr Schutzer said.

Suspicion in Endemic Areas

On Long Island, New York, where Lyme disease is endemic, internist Ian Storch, DO, said he sees “a few cases a season.”

“We have a lot of people over the summer going to the Hamptons and areas out east for the weekend and tick bites are not uncommon,” he said. “People panic.”

He said one thing it’s important to tell patients is that the tick has to be on the skin for 48-72 hours to transmit the disease. If individuals were in a wooded area and were fine before they got there and the tick was attached for less than 2 days, “they’re usually fine.”

Another issue, Dr Storch said, is patients sometimes want to get tested for Lyme disease immediately after a tick bite. But the antibody test doesn’t turn positive for weeks, he noted, and you can get a false-negative result. “If you’re worried and you really want to test, you need to wait 6 weeks to do the blood test.”

In his region, he said that although a tick bite is a red flag, he may also suspect Lyme disease when a patient presents with otherwise unexplained joint pain, weakness, lethargy, or fever. “In our area, those are things that would make you test for Lyme.”

He also urged consideration of Lyme in this new age of long COVID. Weakness, fatigue, and lethargy are also classic symptoms of long COVID, he noted. “Keep Lyme disease in your differential because there is a lot of overlap with chronic Lyme disease,” Dr Storch said.

Discerning Lyme From Southern Tick–Associated Rash Illness

Bonnie M. Word, MD, director of the Houston Travel Medicine Clinic in Texas, where Lyme disease is not endemic, said Lyme disease “will not and should not be on the initial differential diagnosis for those residing in nonendemic areas unless a history of travel to an endemic area is obtained.”

She noted the typical EM rash may not be as distinct or easy to discern on black and brown skin. In addition, she said, EM may have many variations in presentation, such as a crusted center or faint borders, which could lead to a delay in diagnosis and treatment. She suggested consulting the CDC guidance on Lyme disease rashes.

Another challenge in diagnosis, she said, is the patient who presents with what appears to be a classic EM lesion but does not live in a Lyme-endemic area. In Texas, Southern Tick–Associated Rash Illness (STARI) may present with a similar lesion, she said.

“It is transmitted by the lone star tick, which is found in the southeast and south-central US,” Dr Word said. “However, its habitat is moving northward and westerly,” she said.

Adding Lyme disease to the differential diagnosis is reasonable, she said, if a patient presents with neurologic symptoms “such as a facial palsy, meningitis, radiculitis, and carditis if in addition to their symptoms there is evidence of an epidemiologic link to a Lyme-endemic region.”

She noted that a detailed travel history is important as “Lyme is also endemic in Eastern Canada, Europe, states of the former Soviet Union, China, Mongolia, and Japan.”

Primary care physicians play a critical role in evaluating, diagnosing, and treating most cases of early Lyme disease, thus limiting the number of people who will develop disseminated or late Lyme disease, she said. “The two latter manifestations are most often treated by infectious disease, neurology, or rheumatology specialists.”

Dr Schutzer said he hopes the paper serves as a refresher for those physicians who regularly see Lyme disease cases and also helps those newly included in the disease’s spreading regions.

“The earlier you diagnose it, the earlier you can treat it and the better the chance for a favorable outcome,” he said.

Dr Schutzer, Dr Coyle, Dr Storch, and Dr Word reported no relevant financial relationships.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.