Emerging Tick-Borne Illnesses: Not Just Lyme Disease Part 3 Ehrlichiosis




  • Overall annual incidence noted to be 3.2 cases per million in the United States between 2008 and 2012 (Biggs 2016)
  • Highest incidence occurs in those 60-69 years of age (Biggs 2016)


  • Median age is 55 years of age with 64% of cases reported in Caucasian patients (Heitman 2016)


  • Slight male to female predominance (Heitman 2016)


  • Case fatality rate is estimated to be 0.7-1% overall (Heitman 2016).
    • Case fatality rate is highest in those over under 5 years of age and over 70 years of age

Geography and Seasonality (Heitman 2016): Cases most frequently reported in the Southeastern and Southcentral United States

  • Six States account for over 54% of all reported cases
    • Oklahoma
    • Missouri
    • Delaware
    • Arkansas
    • Missouri
    • Tennessee
  • Seasonal distribution is concentrated from May through July

Poor Prognostic Factors (Biggs 2016):

  • Increased Age
  • Immunocompromised States
  • Delays in diagnosis and treatment
  • Use of sulfonamide antimicrobial

Pathogenesis (Biggs 2016):

  • After tick transmissibility, chaffennis, an obligate intracellular bacterial, has a predilection for monocytes and tissue macrophages, specifically neutrophils
  • Once infected, the organism multiplies within cytoplasmic membrane-bound vacuoles forming clusters of bacterial called morulae
  • Infection elicits a systemic inflammatory response with multiorgan involvement, particularly the spleen, lymphatic system, and bone marrow

History and Physical:

Symptoms (Biggs 2016):

  • Symptoms typically appear 5-14 days after bite of an infected tick
  • Rash is present more often than Anaplasmosis
    • Present in up to 1/3rd of patients
    • Typically occurs 5 days after illness onset
  • Fever occurs in 96% of recognized cases of ehrlichiosis along with other non-specific flu-like symptoms:
    • Headache
    • Malaise
    • Myalgias
  • Gastrointestinal symptoms are often seen unlike Anaplasmosis
    • Very commonly seen in children
  • Respiratory symptoms or Cough is present in approximately 28% of patients
  • Central Nervous System involvement is present in approximately 20% of patients
    • Meningitis and Meningoencephalitis
  • Severe Manifestations: Most cases are self-limiting, but Ehrlichiosis has been associated with the following severe disease manifestations:
    • Shock
    • Renal Failure
    • Hepatic Failure
    • Coagulopathy
    • Hemorrhagic Manifestations
    • Hemophagocytic Syndromes
    • ARDS


Labs: Characteristic laboratory findings are seen in Ehrlichiosis along fever and non-specific flu-like illness:

  • Leukopenia
  • Thrombocytopenia
  • Mild Anemia: Occurs later in illness than thrombocytopenia or leukopenia
  • Mild to Moderate Elevated Hepatic Transaminase
  • Mild to Moderate Hyponatremia

Blood Smear:

  • May see morulae with microscopic examination of blood smears but blood smear may be relatively insensitive and inconsistent and is dependent on operator experience (Biggs 2016)
  • Observation of morulae is seen much less commonly than in Anaplasmosis

Confirmatory Testing:

  • Serological testing of IgM and IgG antibodies using indirect immunofluorescence assay (IFA) is available for diagnosis
  • RT-PCR assays is available for diagnosis and is most sensitive during the first week of illness and is the test of choice
  • Immunohistochemical staining of skin, tissue, or bone marrow biopsies has also been used for diagnosis

Guest Post By:

Akash Ray, DO
PGY-2 Emergency Medicine Resident Inspira Medical Center
Vineland, NJ
Twitter: @_kashray


  1. Biggs H et al. Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis – United States. MMWR Recomm Rep. 2016. PMID: 27172113
  2. Heitman N at al. Increasing Incidence of Ehrlichiosis in the United States: A Summary of National Surveillance of Ehrlichia chaffeensis and Ehrlichia ewingii Infections in the United States, 2008-2012. Am J Trop Med Hyg. 2016. PMID: 26621561

Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)

Cite this article as: Muhammad Durrani, "Emerging Tick-Borne Illnesses: Not Just Lyme Disease Part 3 Ehrlichiosis", REBEL EM blog, November 4, 2020. Available at: https://rebelem.com/emerging-tick-borne-illnesses-not-just-lyme-disease-part-3-ehrlichiosis/.
The following two tabs change content below.

Muhammad Durrani

Assistant Clerkship Director & Assistant Research Director at Inspira Medical Center

Like this article?

Share on facebook
Share on Facebook
Share on twitter
Share on Twitter
Share on linkedin
Share on Linkdin
Share on email
Share via Email

Want to support rebelem?

Leave a Comment

Time limit is exhausted. Please reload CAPTCHA.