Smith, Jami S. MPA, MEd, PA-C; Ziegler, Rachel; Didas, Colleen M. MPH, MMS, PA-C
* Lyme disease is the most common vector-borne illness in North America and Europe.
* The highest incidence is in boys ages 5 to 14 years. Cases are concentrated in the northeast and north-central United States.
* Borrelia burgdorferi, a bacterial spirochete, is the causative agent of Lyme disease. Ixodes scapularis and Ixodes pacificus (commonly known as deer ticks or blacklegged ticks) feed on the blood of animal reservoir hosts and become infected with B. burgdorferi. Infected ticks then transmit the disease to human hosts.
* Lyme disease is most likely to occur from May to September, when ticks are in the nymphal stage.
* Stages of the disease depend on time since infection and are differentiated by characteristic signs and symptoms.
* Early localized stage occurs 3 to 30 days after tick exposure and is characterized by an erythema migrans rash, fever, fatigue, arthralgias, and myalgias.
* Early disseminated stage occurs weeks to months after the tick bite, when bacteria enter the bloodstream and are deposited in distant sites within the body. This stage presents with the same signs and symptoms as the early localized stage; patients also may have additional symptoms due to Lyme carditis or Lyme neuroborreliosis.
* The late disseminated stage occurs weeks to years after the initial exposure, when the infection has spread throughout the body. Symptoms are typically due to Lyme arthritis and neurologic manifestations including encephalitis, encephalopathy, and polyneuropathy.
* Identifying and treating Lyme disease during pregnancy is important, as significant associations have been found between untreated Lyme disease and adverse pregnancy outcomes, including spontaneous abortion, stillbirth, and preterm births. Avoid doxycycline in pregnant women; the recommended treatment is amoxicillin.
* Identify the geographic location, outdoor activities, and whether the tick was on the patient's body for more than 36 hours.
* The incubation period for Lyme disease is usually 1 to 2 weeks but may be shorter or longer.
* Patients may complain of arthralgias, myalgias, and fever depending on their stage of Lyme disease. In advanced cases, they may complain of cardiac, neurologic, or musculoskeletal symptoms.
* Physical examination
* Patients may present with a classic, target-like rash with a red outer ring and central clearing at the site of the tick bite. These erythema migrans lesions occur in about 80% of affected patients, typically are asymptomatic, often are expanding, and can range in diameter from the size of a dime to the full width of a patient's back.
* Low-grade fever and regional lymphadenopathy may also be present.
* Additional physical examination findings that may be indicative of a later disease stage include:
* Signs of nuchal rigidity, Bell palsy, and altered sensation in a patient with Lyme neuroborreliosis.
* Signs of cardiac dysrhythmia, including near-syncope, anxiety, and tachypnea; significant atrioventricular nodal dysfunction and heart block may occur with Lyme carditis.
* Swollen, warm joints, most typically the knees, which may indicate Lyme arthritis in advanced cases.
* Diagnosis is heavily dependent on clinical suspicion, recognized signs and symptoms of Lyme disease, and inclusion of Lyme in the clinician's differential diagnosis.
* Patients who present with the following circumstances should not have diagnostic testing:
* Presence of tick for less than 24 hours (transmission of bacteria usually requires 36 hours of tick attachment); patients with tick exposures of less than 24 hours are strongly unlikely to have contracted Lyme disease.
* Presence of erythema migrans and history of tick bite, which warrants automatic initiation of treatment.
* Patients presenting with nonspecific symptoms and no history of known tick exposure.
* Diagnosis of early localized disease:
* The standard serologic testing procedure, as defined by the CDC, involves a two-tiered approach to accurately identify active disease and previous infection.
* Enzyme-linked immunosorbent assay (ELISA) or immunofluorescent assay (IFA) is recommended as the initial test of choice. Specimens negative by ELISA or IFA do not require further testing.
* Western blot testing should be performed to confirm positive EIA or IFA tests. IgM and IgG B. burgdorferi antibodies may persist for many years after successful treatment of Lyme disease; thus, persistent seropositivity is not necessarily an indication of treatment failure.
* Diagnosis of early disseminated disease:
* In addition to the serologic testing for early localized disease, additional testing includes an ECG to detect evidence of AV nodal dysfunction or heart block. If meningitis is suspected, obtain a cerebrospinal fluid analysis.
* Diagnosis of late disseminated disease:
* In addition to the serologic testing for early localized disease, additional testing includes analysis of joint fluid for suspected Lyme arthritis and cerebrospinal fluid analysis and MRI if the patient has neurologic symptoms concerning for encephalitis.
* Routine use of antimicrobial prophylaxis or serologic testing is not recommended for prevention of Lyme disease after a recognized tick bite. Instead, start treatment for the appropriate stage of Lyme disease.
* A single prophylactic 200-mg dose of doxycycline may be prescribed to adults, and a dosage of 4 mg/kg up to the maximum of 200 mg for children age 8 years and older, when all of the following criteria are met:
* the attached tick can be reliably identified as an adult or nymphal stage I. scapularis tick that is estimated to have been attached for 36 hours or longer. This estimation is made on the basis of the degree of the tick's engorgement with blood, or if the patient is certain about the time of exposure to the tick
* prophylaxis can be started within 72 hours of the time that the tick was removed
* ecological information indicates that the local rate of infection of these ticks with B. burgdorferi is 20% or more
* doxycycline treatment is not contraindicated. Doxycycline is not recommended in pregnant and lactating women and children under age 8 years.
* Early localized or early disseminated Lyme disease: For adults who have erythema migrans but no specific neurologic manifestations or advanced atrioventricular heart block, administer 100 mg of doxycycline twice per day for 14 days (range, 10 to 21 days). Alternatives include amoxicillin (500 mg three times per day) or cefuroxime axetil (500 mg twice per day) for 14 days (range, 14 to 21 days).
* Lyme carditis: Hospitalization and continuous monitoring are advised for symptomatic patients (those with syncope, dyspnea, or chest pain) and patients with second- or third-degree atrioventricular block. A parenteral antibiotic, such as ceftriaxone, is recommended as initial treatment of hospitalized patients. A temporary pacemaker may be required for patients with advanced heart block.
* Lyme arthritis: Adults without clinical evidence of neurologic disease usually can be treated successfully with 100 mg of doxycycline twice per day for 28 days.
* Lyme neurologic disease: Adults with Lyme disease affecting the central or peripheral nervous system should be treated with IV ceftriaxone for 2 to 4 weeks. Cefotaxime or penicillin G administered IV are alternatives, with limited support for doxycycline as an alternative in select patients.
© 2014 American Academy of Physician Assistants.