Ehrlichiosis

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Ehrlichiosis
ICD-10 A79.8
ICD-9 082.4
DiseasesDB 31663
MedlinePlus 001381
MeSH D016873
This page is about clinical aspects of the disease.  For microbiologic aspects of the causative organism(s), see Ehrlichia.

Ehrlichiosis Microchapters

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Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Ehrlichiosis from other Diseases

Epidemiology and Demographics

Risk Factors

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Prevention

Case Studies

Case #1

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2]

Synonyms and keywords: Sennetsu fever; human granulocytic ehrlichiosis; Anaplasma phagocytophilum; Ehrlichia phagocytophila; human monocytic ehrlichiosis

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Ehrlichiosis from other Diseases

Epidemiology and Demographics

Risk Factors

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms | Physical Examination | Laboratory Findings | Other Imaging Findings | Other Diagnostic Studies

Treatment

Medical Therapy | Surgery | Primary Prevention | Secondary Prevention | Future or Investigational Therapies

Case Studies

Case#1


Pathophysiology

  • Ehrlichia are transported between cells through the host cell filopodia during initial stages of infection, whereas, in the final stages of infection the pathogen ruptures the host cell membrane.[1]
  • Most of the symptoms of Ehrlichiosis can likely be ascribed to the immune dysregulation that it causes.
  • Early in infection, production of TNF-alpha, a cellular product that promotes inflammation and immune response, is suppressed. Experiments in mouse models further supports this hypothesis, as mice lacking TNF-alpha I/II receptors are resistant to liver injury caused by ehrlichia infection.[2]
  • Late in infection, however, production of this substance can be upregulated by 30 fold, which is likely responsible for the "toxic shock-like" syndrome seen in some severe cases of ehrlichiosis.

Causes

Five species of the genus Ehrlichia have been shown to cause human infection:[3]

The latter two infections are not well studied.

Epidemiology and Demographics

  • The average reported annual incidence is 0.7 cases per million population.[4]
  • A. phagocytophilium is endemic to New England and the north central and Pacific regions of the United States.
  • E. chaffeensis is most common in the south central and southeastern states.
  • E. ewingii is most common in the south central and southeastern states.

The lone star tick (Amblyomma americanum) is the primary vector of both Ehrlichia chaffeensis and Ehrlichia ewingii in the United States [5].

Risk Factors

Risk factors for ehrlichiosis include:

  • Living near an area with a lot of ticks
  • Owning a pet that may bring a tick home
  • Walking or playing in high grasses

Natural History, Complications and Prognosis

Complications

Diagnosis

Symptoms

Other possible symptoms include:

A rash appears in fewer than half of cases.

Physical Examination

Vitals

Skin

Head

Laboratory Findings

Treatment

  • Early clinical experience suggested that chloramphenicol may also be effective, however in vitro susceptibility testing revealed resistance.

Antimicrobial regimen

  • Preferred regimen: Doxycycline 100 mg PO/IV q12h for 7-14 days
  • Note: Patients should be treated for at least 3 days after the fever subsides and until there is evidence of clinical improvement
  • Alternative regimen (1): Chloramphenicol 500mg PO qid
  • Alternative regimen (2): Rifampin 600 mg PO/IV qd for 7-10 days
  • 2.1 ≥ 8 years old
  • Preferred regimen: Doxycycline 2 mg/kg IV/PO q12h (Maximum, 200 mg/day) for 10 days
  • 2.2 < 8 years old without Lyme disease
  • Preferred regimen: Doxycycline 2 mg/kg IV/PO q12h (Maximum, 200 mg/day) for 4-5 days (or 3 days after resolution of fever)
  • 2.3 co-infected with Lyme disease
  • Preferred regimen: Doxycycline, then Amoxicillin 50 mg/kg in 3 divided doses (Maximum, 500 mg/dose) OR Cefuroxime 30 mg/kg in 2 divided doses (Maximum, 500 mg/dose) for 14 days

References

  1. Thomas S, Popov VL, Walker DH (2010). Kaushal, Deepak, ed. "Exit Mechanisms of the Intracellular Bacterium Ehrlichia". PLoS ONE. 5 (12): e15775. doi:10.1371/journal.pone.0015775. PMC 3004962. PMID 21187937.
  2. McBride, Jere W. (31 January 2011). "Molecular and cellular pathobiology of Ehrlichia infection: targets for new therapeutics and immunomodulation strategies". Expert Reviews in Molecular Medicine. 13. doi:10.1017/S1462399410001730. Unknown parameter |coauthors= ignored (help)
  3. Dumler JS, Madigan JE, Pusterla N, Bakken JS (2007). "Ehrlichioses in humans: epidemiology, clinical presentation, diagnosis, and treatment". Clin. Infect. Dis. 45 (Suppl 1): S45–51. doi:10.1086/518146. PMID 17582569. Unknown parameter |month= ignored (help)
  4. 4.0 4.1 4.2 Goddard J (September 1, 2008). "What Is New With Ehrlichiosis?". Infections in Medicine.
  5. Thomas, Rachael J (1 August 2009). "Current management of human granulocytic anaplasmosis, human monocytic ehrlichiosis and ehrlichiosis". Expert Review of Anti-infective Therapy. 7 (6): 709–722. doi:10.1586/eri.09.44. PMC 2739015. PMID 19681699. Unknown parameter |month= ignored (help); Unknown parameter |coauthors= ignored (help)
  6. Marty AM, Dumler JS, Imes G, Brusman HP, Smrkovski LL, Frisman DM (1995). "Ehrlichiosis mimicking thrombotic thrombocytopenic purpura. Case report and pathological correlation". Hum. Pathol. 26 (8): 920–5. doi:10.1016/0046-8177(95)90017-9. PMID 7635455. Unknown parameter |month= ignored (help)
  7. Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580.


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