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* ''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.<ref>{{cite journal |author=Thomas S, Popov VL, Walker DH |title=Exit Mechanisms of the Intracellular ''Bacterium Ehrlichia'' |journal=PLoS ONE |volume=5 |issue=12 |pages=e15775 |year=2010|url=http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0015775 |doi=10.1371/journal.pone.0015775 |pmid=21187937 |pmc=3004962|editor1-last=Kaushal |editor1-first=Deepak}}</ref>
* ''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.<ref>{{cite journal |author=Thomas S, Popov VL, Walker DH |title=Exit Mechanisms of the Intracellular ''Bacterium Ehrlichia'' |journal=PLoS ONE |volume=5 |issue=12 |pages=e15775 |year=2010|url=http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0015775 |doi=10.1371/journal.pone.0015775 |pmid=21187937 |pmc=3004962|editor1-last=Kaushal |editor1-first=Deepak}}</ref>
* Most of the symptoms of ehrlichiosis can likely be ascribed to the immune dysregulation that it causes.
* 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.
* Early in infection, production of [[TNF-alpha]], a cellular product that promotes [[inflammation]] and immune response, is suppressed.
* 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.
* 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==
==Causes==

Revision as of 07:19, 2 August 2012

Sennetsu fever
ICD-9 082.4
MeSH D016873

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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]

Overview

Ehrlichiosis is a tickborne[1]bacterial infection,[2] caused by bacteria of the family Anaplasmataceae, genera Ehrlichia and Anaplasma. These obligate intracellular bacteria infect and kill white blood cells.

Historical Perspective

  • In 2008, human infection by Panola Mountain (Georgia, USA) Ehrlichia species was reported.[3]
  • On August 3, 2011, infection by a yet-unnamed bacterium in the genus Ehrlichia carried by deer ticks that has caused flu-likesymptoms in at least 25 people in Minnesota and Wisconsin was reported; human ehrlichiosis was thought to be very rare or absent in Minnesota and Wisconsin.[4] The new species, which is very similar genetically to an Ehrlichia species found in Eastern Europe and Japan called E. muris, was identified at Mayo Clinic Health System's Eau Claire hospital.[4]

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.[5]
  • 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.
  • 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 (see note below) species of the genus Ehrlichia have been shown to cause human infection:[6]

The latter two infections are not well studied.

Epidemiology and Demographics

The average reported annual incidence is 0.7 cases per million population.[7]

Diagnosis

Symptoms


Ehrlichiosis can also blunt the immune system, which may lead to opportunistic infections such as candidiasis. Some cases can present with purpura and in one such case the organisms were present in such overwhelming numbers that in 1991 Dr. Aileen Marty of the AFIP was able to demonstrate the bacteria in human tissues using standard stains, and later proved that the organisms were indeed Ehrlichia using immunoperoxidase stains.[8]

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.[9]

3% of human monocytic ehrlichiosis cases result in death, however these deaths occur "most commonly in immunosuppressed individuals who develop respiratory distress syndrome, hepatitis, or opportunistic nosocomial infections."[10]

Treatment

Doxycycline is the drug of choice. For people allergic to drugs of the tetracycline class, rifampicin is an alternative.[7] Early clinical experience suggested that chloramphenicol may also be effective, however in vitro susceptibility testing revealed resistance.

References

  1. CDC "Questions and Answers" page for tickborne rickettsial diseases
  2. Dawson, Jacqueline E., Marty, Aileen M. (1997). "Ehrlichiosis". In Horsburgh CR, Nelson AM. Pathology of emerging Infections. 1. American Society for Microbiology.
  3. Reeves WK, Loftis AD, Nicholson WL, Czarkowski AG (2008). "The first report of human illness associated with the Panola Mountain Ehrlichia species: a case report". Journal of medical case reports. 2: 139. doi:10.1186/1752-1947-2-139. PMC 2396651. PMID 18447934.
  4. 4.0 4.1 Julie Steenhuysen. 2011. New tick-borne bacterium found in upper Midwest. Reuters, 8/3/2011, http://www.trust.org/alertnet/news/new-tick-borne-bacterium-found-in-upper-midwest/, accessed August 4, 2011.
  5. 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.
  6. 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)
  7. 7.0 7.1 7.2 Goddard J (September 1, 2008). "What Is New With Ehrlichiosis?". Infections in Medicine.
  8. 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)
  9. 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)
  10. 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)



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