Tick-borne illnesses are increasing in prevalence and geographic reach. Because the presentation of these illnesses is sometimes nonspecific, they can often be misdiagnosed, especially in the early stages of illness. A detailed history with questions involving recent activities and travel and a thorough physical examination will help narrow the diagnosis. While some illnesses can be diagnosed on clinical findings alone, others require confirmatory testing, which may take days to weeks to result. This issue reviews the emergency department presentation of 9 common tick-borne illnesses and evidence-based recommendations for identification, testing, and treatment.
A 10-year-old girl presents to the ED with left knee swelling and pain. She has been able to walk, but the swelling and pain have become worse over the last 3 to 4 days. The girl says she has not had a fever or chills, and there is no known trauma. The girl’s mother states that her daughter spent 3 weeks at summer camp in Connecticut a few months ago, but otherwise has not traveled recently. On examination, the girl’s knee is swollen, but without erythema or warmth. The girl is able to bear weight, but she is unable to fully flex her knee. X-rays of her knee are significant only for a joint effusion. Should you perform an arthrocentesis of the girl's knee? What lab work would help in making the diagnosis? What are the best treatment options for this patient?
A 5-year-old girl with no past medical history presents to your ED. Her mother noticed that the girl was having difficulty walking today, so she brought her in. She states that her daughter has been complaining that she's tired, and has been saying that her legs feel "weird"after playing in the park yesterday. The mother also mentions that they have a new dog that likes to run in the woods behind their house. On examination, the girl is afebrile with a normal heart rate and respiratory rate. The examination is significant for 3/5 strength in her legs bilaterally, with normal sensation. The girl has had no fever, cough, or congestion. As you consider the possible diagnoses, you begin to wonder whether a lumbar puncture or head imaging is necessary...
An otherwise-healthy 8-year-old boy is brought in by paramedics for altered mental status. He is lethargic, responds only to painful stimuli, and has incomprehensible speech. The child has had fevers, headache, and vomiting for the last 5 days. The boy’s vital signs are as follows: heart rate, 150 beats/min; temperature, 39°C (102.2°F); respiratory rate, 30 breaths/min; oxygen saturation, 98%; and blood pressure, 75/40 mm Hg. On examination, you note a diffuse petechial rash on his trunk, arms, legs, palms, and soles. The boy’s mother tells you the rash has been spreading from his extremities to his abdomen over the last few days. What initial laboratory studies would help you make a diagnosis? What additional complications could arise? Is doxycycline safe for this patient?
Tick-borne illnesses often present a diagnostic challenge for the emergency clinician. Tick bites are usually not painful, and patients are often unaware of the bite1 because the initial local reaction to a tick bite may be similar to the bite of another insect, such as a mosquito or a chigger. Tick-borne illnesses can be easily overlooked on a patient's initial presentation to the emergency department (ED), because the risk and exposure may seem minimal, such as simply playing in the backyard or having a pet that may bring ticks into the house. Nonetheless, many tick-borne illnesses can lead to serious or life-threatening sequelae if left untreated. This issue of Pediatric Emergency Medicine Practice discusses the presentation of 9 tick-borne illnesses, reviews the differential diagnosis for each illness, and provides recommendations for the diagnosis and management of these illnesses in the ED.
A literature search was performed on PubMed using the search terms: pediatric tick, tick-borne illness, tick-borne disease, pediatric Lyme, pediatric Rocky Mountain spotted fever, pediatric tick paralysis, pediatric babesiosis, pediatric ehrlichiosis, Rocky Mountain spotted fever, tick paralysis, babesiosis, ehrlichiosis, anaplasmosis, tularemia, meat allergy tick bite, and red meat tick bite. A total of 177 articles published between 1998 and 2018 were reviewed. The Cochrane Database of Systematic Reviews was searched using the key terms: tick-borne, Lyme, Rocky Mountain spotted fever, tick paralysis, babesiosis, ehrlichiosis, anaplasmosis, tularemia, and tick-borne relapsing fever. This search identified 1 review on the treatment of neurologic manifestations of Lyme disease.
According to standard evidence-level scales, the majority of evidence for tick-borne illnesses falls into the weaker and moderately strong categories. Tick-borne illnesses are relatively rare diseases, particularly in the pediatric population. Currently, there are few randomized controlled trials evaluating treatments for tick-borne illnesses. The majority of studies are based on retrospective and prospective observational studies. There are a number of review articles with recommendations based on observational studies, expert consensus, and case reports on rare complications of tick-borne illnesses. Many of the pediatric recommendations for the diagnosis and management of children with suspected tick-borne illness are based on adult literature.
1. “There was no history of a tick bite, so I don’t have to worry about tick-borne illnesses.”
Tick bites are often painless and may be in locations that are not easily visible. Patients may not give a history of a tick bite; therefore, a careful history to elicit risk factors for tick exposure is necessary, particularly in endemic areas. In studies of tick-borne illnesses, a history of a tick bite was not reported in 30% to 40% of confirmed cases.1,2,26,97,98
4. “I had a strong suspicion that my patient had a tick-borne illness, but I wanted to be sure, so I waited for the confirmatory tests to result before starting her on an antimicrobial.”
For most tick-borne illnesses, confirmatory testing may take days or weeks to result. In patients with a consistent history, examination, and preliminary laboratory findings, empiric treatment may be started while test results are pending. In particular, delayed treatment with doxycycline is associated with a higher mortality rate for RMSF.143 Untreated, RMSF has a case fatality rate of 10% to 25%.144
10. “I’m not in a high-risk area, so I don’t need to consider tick-borne illnesses in my differential.”
While there are areas that are highly endemic for certain diseases, tick-borne illnesses have been reported in all of the contiguous 48 states.154 A thorough travel history is critical to identifying possible tick exposures, as cases acquired during travel to endemic areas may be easily missed.155 Patients may also be exposed during international travel.156,157 Excluding a specific disease based solely on geographic location may delay diagnosis and increase the risk of developing complications.
Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of patients. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.
To help the reader judge the strength of each reference, pertinent information about the study is included in bold type following the reference, where available. In addition, the most informative references cited in this paper, as determined by the author, are highlighted.
Points and Pearls Excerpt
Most Important References
Why to Use
The Rule of 7s has been validated by a retrospective cohort study of 423 children in Lyme-endemic areas. It can help guide clinicians in assessing the need to initiate antibiotic therapy for Lyme meningitis, versus observation and close follow-up care.
When to Use
Use the Rule of 7s in Lyme-endemic areas when considering antibiotic treatment for pediatric patients who:
Abbreviations: CSF, cerebrospinal fluid; RBC, red blood cell; WBC, white blood cell.
This tool should be used to assist clinicians in decision-making, not to replace clinical evaluation of a patient. Patients with scores of 1 to 3 points are not at low risk for Lyme meningitis, and antibiotic therapy for Lyme meningitis should be considered for these patients. Patients with a score of 0 are at low risk for Lyme meningitis; their symptoms may be due to aseptic meningitis or another etiology. Clinicians should use clinical judgment and consider whether the patient has access to adequate follow-up care before initiating antibiotic therapy.
Matthew Lecuyer, MD
The Rule of 7s is meant to aid in the decision to begin antibiotic therapy for suspected Lyme meningitis. It should not replace clinical judgement and clinician assessment of patients.
Avery et al (2006) first derived a clinical prediction model to calculate the probability of Lyme meningitis in children from Lyme-endemic regions, using a statistical analysis of history, physical examiniation, and laboratory findings. Their model was prospectively validated by Garro et al (2009) in a study of 50 children aged 2 to 18 years who lived in a Lyme-endemic region. Fourteen of the children had Lyme meningitis, 6 had possible Lyme meningitis, and 30 were ultimately diagnosed with aseptic meningitis. Categories of low (< 10%), indeterminate (10%-50%), and high (> 50%) probabilities of Lyme meningitis were derived based on the percentage of CSF mononuclear cells, duration of headache, and presence of cranial nerve neuropathy.
The positive predictive value with a cutoff of > 50% probability of Lyme meningitis was 100% (95% confidence interval [CI]: 66%-100%). The negative predictive value with a cutoff of < 10% probability of Lyme meningitis was 100% (95% CI: 82%-100%). The authors noted that when patients had < 7 days of headache, < 70% CSF mononuclear cells, and no seventh or other cranial nerve palsy, the probability of Lyme meningitis was always < 10%, indicating that those patients were at low risk for Lyme meningitis. The authors termed this the Rule of 7s.
The Garro et al study was validated in a large retrospective cohort study by Cohn et al (2012) using electronic medical record data from 3 pediatric emergency departments in Lyme-endemic areas. The sample of 423 children, aged 90 days to 19 years, included 117 children who were diagnosed with Lyme meningitis and 306 who were diagnosed with aseptic meningitis. The specificity of the Rule of 7s for low risk was 41% (95% CI: 36%-47%), and the sensitivity was 96% (95% CI: 90%-99%).
Aris Garro, MD, MPH
Copyright © MDCalc • Reprinted with permission.
Jennifer Bellis, MD, MPH; Ee Tay, MD
Michael Gottlieb, MD, RDMS; Lise Nigrovic, MD, MPH
September 2, 2018
October 1, 2021
4 AMA PRA Category 1 Credits™, 4 ACEP Category I Credits, 4 AAFP Prescribed Credits, 4 AOA Category 2-A or 2-B Credits. Specialty CME Credits: Included as part of the 4 credits, this CME activity is eligible for 4 Infectious Disease CME and 1.5 Pharmacology CME credits
Date of Original Release: September 1, 2018. Date of most recent review: August 15, 2018. Termination date: September 1, 2021.
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