From the Guidelines
Ehrlichiosis should be treated immediately with doxycycline 100mg twice daily for 7-14 days, even before laboratory confirmation in suspected cases, as it can cause severe disease or death, particularly in immunocompromised individuals, the elderly, and young children. The infection is caused primarily by Ehrlichia chaffeensis and Ehrlichia ewingii, and symptoms typically include fever, headache, muscle aches, and fatigue, appearing 1-2 weeks after a tick bite 1. Some patients may develop a rash, though it's less common than in other tick-borne diseases. Diagnosis is based on clinical presentation, history of tick exposure, and laboratory tests including PCR and antibody testing 1. The severity of ehrlichiosis could be related, in part, to host factors such as age and the immune status of the patient, with persons who have compromised immune systems being more frequently hospitalized and having higher case-fatality rates 1.
Key considerations in the management of ehrlichiosis include:
- Prompt initiation of antibacterial treatment with doxycycline, regardless of patient age, including children 1
- Use of PCR amplification of DNA extracted from whole blood for diagnosis during the acute stage 1
- Consideration of the patient's immune status and potential for severe disease or fatal outcomes 1
- Prevention measures, such as using tick repellents, wearing protective clothing, and performing regular tick checks 1
It is essential to note that delays in recognition and initiation of appropriate antibacterial treatment may contribute to increased mortality, particularly in immunosuppressed patients 1. Therefore, treatment should not be delayed while awaiting laboratory confirmation, and doxycycline should be started immediately in suspected cases.
From the Research
Ehrlichiosis Overview
- Ehrlichiosis is a potentially fatal disease caused by Ehrlichia chaffeensis and Ehrlichia ewingii, with cases increasing in the United States 2.
- The incidence rate of E. chaffeensis infections was 3.2 cases per million person-years, with a hospitalization rate of 57% and a case fatality rate of 1% 2.
- Ehrlichiosis can present as undifferentiated fever, but thrombocytopenia, leukopenia, and increased serum transaminase activities are important laboratory features 3.
Risk Factors and Outcomes
- Delay in initiation of doxycycline therapy is a significant factor associated with severe ehrlichiosis, with an increased risk for ICU admission 4, 5.
- Documentation of tick exposure was independently associated with a decreased risk for ICU admission 4.
- Patients with a delay in doxycycline treatment were more likely to present with an abnormal lung exam and altered mental status, and had a significantly increased rate of transfer to the intensive care unit and requirement for mechanical ventilation 5.
Epidemiology
- The overall rate for ehrlichiosis has increased 4-fold since 2000, with 4,613 cases of E. chaffeensis infections reported through the Nationally Notifiable Diseases Surveillance System during 2008-2012 2.
- E. ewingii ehrlichiosis was reported more commonly among older, White, non-Hispanic, and male patients, with the highest number of cases reported from Missouri and Arkansas 6.
- Children aged < 5 years had the highest case fatality rate of 4% 2.
Treatment and Prevention
- Early treatment with doxycycline is crucial in reducing the severity of ehrlichiosis, with empiric antibiotic therapy recommended for patients with a high suspicion of ehrlichiosis 3, 5.
- Clinician education is essential to implement molecular assays to properly diagnose E. ewingii infection in patients and gain a better understanding of the epidemiology of this emerging disease 6.