This transcript has been edited for clarity.
Summer is nearly here, and that means it's time for hiking, playing outdoors, and ticks. Fortunately, the Infectious Diseases Society of America (IDSA) recently updated its guidelines on the diagnosis and treatment of Lyme disease.
Lyme disease is a tick-borne infection caused by the Borrelia burgdorferi spirochete and transmitted to humans by the bite of the Ixodes tick.
Let's go over the clinical presentation. Lyme disease typically includes a skin lesion at the site of the tick bite, called the erythema migrans (EM) lesion. Disseminated disease can have multiple skin lesions over the body, and about two thirds of people also have systemic symptoms: fatigue, arthralgias, myalgias, and headache. Lyme disease, particularly when it is advanced, can manifest with neurologic and cardiac symptoms as well as an inflammatory arthritis.
If someone is bitten by a tick and the tick is still attached, the best way to remove the tick is to grab it with a forceps or tweezers right at the point of insertion, and then pull. Don't burn it off.
Two Frequently Asked Questions
Two questions that come up a lot in the office are (1) whether someone who is bitten by a tick needs diagnostic testing, and (2) should these patients receive antibiotic prophylaxis? First, there is no reason to do diagnostic testing; even if they have Lyme disease, the test will probably be negative early on in disease, and there is a high risk for false-positive tests in tick-endemic areas.
Second, prophylaxis. When someone is bitten by a tick, we need to ask how long the tick was attached. Transmission is very unlikely if the tick was attached for less than 24 hours. For ticks that have been attached more than a day, one meta-analysis showed that administration of prophylactic doxycycline within 72 hours of removal of the tick reduces the risk for subsequent Lyme disease from 2.2% to 0.2%. Therefore, the guidelines recommend that prophylactic antibiotic therapy be given to adults and children when it can be given within 72 hours of removal of an identified high-risk tick bite. High-risk tick bites are those from a deer tick in an endemic area that were attached for 36 hours or more. If used, prophylaxis should be a single dose of doxycycline 200 mg.
For patients with early Lyme disease, an EM rash with or without systemic symptoms, clinical diagnosis is recommended over lab testing. This is because only about 20% of people have a positive Lyme test early in disease when they present with an EM lesion. If the lesion is atypical in appearance and the diagnosis is uncertain, then antibody testing can be done. The important point to remember here is that because of the high likelihood of false-negative tests early on, if the initial test is negative, it should be repeated about a month later.
For early Lyme disease, the recommended antibiotics are a 10-day course of doxycycline, or a 14-day course of amoxicillin or cefuroxime axetil. They are all equally effective. If someone can't take doxycycline or a beta-lactam, then a 7-day course of azithromycin is the preferred second-line agent.
Remember: Doxycycline is generally avoided in children younger than 8 years of age, in pregnancy, and in breastfeeding women because of concern for staining of permanent teeth. Both the IDSA and the American Academy of Pediatrics say that doxycycline can be used in children if needed. Beta-lactam antibiotics should be used as first-line therapy in these groups, with doxycycline as a second-line choice if there are allergies to beta-lactams. I use amoxicillin as my go-to treatment for most patients when treating Lyme disease because doxycycline can cause a phototoxic reaction, which can be a problem for patients during the spring and summer.
This is important information to have at your fingertips now that spring is here and summer is coming.
I'm Neil Skolnik, and this is Medscape.
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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Lyme Disease: The Latest Guidelines on Testing, Prophylaxis, and Treatment - Medscape - Jun 04, 2021.