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| __NOTOC__
| | #redirect:[[Ehrlichiosis]] |
| {{Infobox Disease
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| | Name = {{PAGENAME}}
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| | Image =
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| | Caption =
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| | DiseasesDB = 31663 |
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| | ICD10 = {{ICD10|A|79|8|a|75}} |
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| | ICD9 = {{ICD9|082.4}}
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| | ICDO =
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| | OMIM =
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| | MedlinePlus = 001381 |
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| | eMedicineSubj =
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| | eMedicineTopic =
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| | MeshID = D016873
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| }}
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| {{SI}}
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| {{CMG}}; {{AE}} {{RT}}
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| ==Overview==
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| '''Ehrlichiosis''' is a [[Tick-borne disease|tickborne]]<ref>[http://www.cdc.gov/ticks/diseases/ehrlichiosis/faq.html#howget CDC "Questions and Answers" page for tickborne rickettsial diseases]</ref>bacterial infection,<ref>{{cite book |author=Dawson, Jacqueline E., Marty, Aileen M. |chapter=Ehrlichiosis |editor=Horsburgh CR, Nelson AM |title=Pathology of emerging Infections |publisher=American Society for Microbiology |year=1997 |volume=1 }}</ref> caused by bacteria of the family [[Anaplasmataceae]], genera ''[[Ehrlichia]]'' and ''[[Anaplasma]]''. These [[Obligate intracellular parasite|obligate intracellular]] [[bacteria]] infect and kill the [[white blood cell]]s.
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| ==Historical Perspective==
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| * In 2008, human infection by [[Panola Mountain]] (Georgia, USA) ''Ehrlichia'' species was reported.<ref>{{cite journal |author=Reeves WK, Loftis AD, Nicholson WL, Czarkowski AG |title=The first report of human illness associated with the Panola Mountain Ehrlichia species: a case report |journal=Journal of medical case reports |volume=2 |pages=139 |year=2008 |pmid=18447934 |pmc=2396651 |doi=10.1186/1752-1947-2-139|url=http://www.jmedicalcasereports.com/content/2//139}}</ref>
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| * On August 3, 2011, infection by a yet-unnamed bacterium in the genus ''Ehrlichia'' carried by [[deer tick]]s that has caused [[flu-like]]symptoms 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.<ref name="Steenhuysen, 2011">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.</ref> 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.<ref name="Steenhuysen, 2011" />
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| * 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.
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| ==Pathophysiology==
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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>
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| * Most of the symptoms of ehrlichiosis can likely be ascribed to the immune dysregulation that it causes.
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| * 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.<ref>{{cite journal|last=McBride|first=Jere W.|coauthors=Walker, David H.|title=Molecular and cellular pathobiology of Ehrlichia infection: targets for new therapeutics and immunomodulation strategies|journal=Expert Reviews in Molecular Medicine|date=31 January 2011|volume=13|doi=10.1017/S1462399410001730}}</ref>
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| * 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.
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| ==Causes==
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| Five (see '''note''' below) species of the genus Ehrlichia have been shown to cause human infection:<ref>{{cite journal |author=Dumler JS, Madigan JE, Pusterla N, Bakken JS |title=Ehrlichioses in humans: epidemiology, clinical presentation, diagnosis, and treatment |journal=Clin. Infect. Dis. |volume=45 |issue=Suppl 1 |pages=S45–51 |year=2007 |month=July |pmid=17582569 |doi=10.1086/518146|url=http://www.cid.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=17582569}}</ref>
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| * ''[[Anaplasma phagocytophilum]]'' (which causes [[human granulocytic anaplasmosis]], formerly known as human granulocytic ehrlichiosis).
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| * ''[[Ehrlichia ewingii]]'' (which causes [[human ewingii ehrlichiosis]]). ''E. ewingii'' primarily infects deer and dogs (see [[Ehrlichiosis (canine)]]).<ref name="Goddard"/>
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| * ''[[Ehrlichia chaffeensis]]'' (which causes [[human monocytic ehrlichiosis]]).
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| * ''[[Ehrlichia canis]]''
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| * ''[[Neorickettsia sennetsu]]''
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| The latter two infections are not well studied.
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| ==Epidemiology and Demographics==
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| * The average reported annual incidence is 0.7 cases per million population.<ref name="Goddard">{{cite journal |author=Goddard J |title=What Is New With Ehrlichiosis?|journal=Infections in Medicine|date=September 1, 2008 |url=http://www.consultantlive.com/headache/article/1145625/1405478}}</ref>
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| * ''A. phagocytophilium'' is endemic to New England and the north central and Pacific regions of the United States.
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| * ''E. chaffeensis'' is most common in the south central and southeastern states.
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| * ''E. ewingii'' is most common in the south central and southeastern states.
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| ==Natural History, Complications and Prognosis==
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| ===Complications===
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| * [[Acute respiratory distress syndrome|Respiratory distress syndrome]]
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| * [[Hepatitis]]
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| * [[Candidiasis]]
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| * Opportunistic [[nosocomial infection]]s<ref>{{cite journal|last=Thomas|first=Rachael J|coauthors=Dumler, J Stephen, Carlyon, Jason A|title=Current management of human granulocytic anaplasmosis, human monocytic ehrlichiosis and ehrlichiosis|journal=Expert Review of Anti-infective Therapy|date=1 August 2009|year=2009|month=August|volume=7|issue=6|pages=709–722|doi=10.1586/eri.09.44|pmid=19681699|pmc=2739015}}</ref>
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| * [[Death]]
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| ==Diagnosis==
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| ===Symptoms===
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| * [[Headache]]
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| * [[Muscle aches]]
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| * [[Fatigue]]
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| * A [[rash]] may occur, but is uncommon.
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| ===Physical Examination===
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| ====Skin====
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| * [[Rash]]
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| * [[Purpura]] - can be a presenting feature. <ref>{{cite journal |author=Marty AM, Dumler JS, Imes G, Brusman HP, Smrkovski LL, Frisman DM |title=Ehrlichiosis mimicking thrombotic thrombocytopenic purpura. Case report and pathological correlation |journal=Hum. Pathol. |volume=26 |issue=8 |pages=920–5 |year=1995 |month=August |pmid=7635455 |url=http://www.humanpathol.com/article/0046-8177(95)90017-9/abstract |doi=10.1016/0046-8177(95)90017-9}}</ref>
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| ==Treatment==
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| [[Doxycycline]] is the drug of choice. For people allergic to drugs of the [[tetracycline]] class, [[rifampicin]] is an alternative.<ref name="Goddard"/> Early clinical experience suggested that [[chloramphenicol]] may also be effective, however in vitro susceptibility testing revealed [[resistance]].
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| ==References==
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| {{reflist|2}}
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| [[Category:Bacterium-related cutaneous conditions]]
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| [[Category:Tick-borne diseases]]
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| [[Category:Disease]]
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| {{WH}}
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| {{WS}}
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