Download - Lecture Rickettsia; Coxiella
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RICKETTSIA
AND
COXIELLAProf. Khalifa Sifaw Ghenghesh
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Rickettsia species
Gram-negative bacilli
Obligateintracellularparasites
Allassociated withanarthropodvector
Pathogenicspeciesparasitizeendothelialcellsalmostexclusively
2antigenicallydistinctgroups Typhusgroup
Spotted fevergroup
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Pathogenesis
Theorganismsenterthe bodythroughthe biteor faecesofan
infectedarthropodvector Disseminatethrough bloodstream
>> endothelialcells byinducedphagocytosis >> escape from
phagosome >> multiplyintra-cellularly >> destroyhostcell
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Flea-borne fevers (Murinetyphus) R. typhi
Ratsandtheirinfected fleas
Tropicalandsubtropicalcoastalregions
Ports withlargenumberofrats
Disease:similartoepidemictyphusbutmilder
Tick-bornespotted fever (group)
Example:R. rickettsii Can belife-threatening
Maintainedinenzooticcycle (ticksandtheir wildanimalhosts)
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Scrub typhus
Orientia tsutsugamushi(previouslyR. tsutsugamushi)
Larvalstages (chiggers) ofmites(Leptotrombidium)
Hosts:Ratsorothersmallmammals
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Laboratory Diagnosis
SerologicalMethods
Weil-Felixtest (Agglutinationtest)
Somatic Agsofnon-motileProteus
species
Notreliable >> low levelsofsensitivityandspecificity
Detectionof AbstoRickettsia species by:
Immunofluorescence Latexagglutination
Enzymeimmuno-assay
Deathmayoccur beforedetectablelevelsof Abarepresent
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IsolationoftheOrganism
Incellculture Insusceptiblelaboratoryanimal
Notpracticle
Detectionoftheorganismintissue Specimen:Skin biopsies from
petechiallesions Examined by:
Immuno-fluorescenceor
immuno-enzymemethods
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Treatment
Rickettsiostaticantibiotics
Tetracyclines
Chloramphenicol Intensivenursingcareandmanagementof fluidsand
electrolytes
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Child'srighthandand wristdisplayingthecharacteristicspottedrashofRockyMountain
spotted fevercaused byRickettsia rickettsii
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Rickettsia tsutsugamushifree withinthecytoplasmofamouse braincapillary
endothelialcell.Capillary wallappearsincrosssection
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Dorsalview ofanAmerican Dog Tick,Dermacentor variabilis, aknowncarrierof
RockyMountainSpotted
Fevercaused bythebacteriumRickettsia rickettsii.
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IFA reactionofapositivehumanserumonRickettsia rickettsiigrowninchicken
yolksacs, 400X
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RedstructuresindicateimmunohistologicalstainingofRickettsia rickettsiiinendothelialcellsofa bloodvessel fromapatient with
fatalRMSF
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Removing attached ticksRemoving attached ticks
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Coxeilla burnetii
Gram-negative, Pleomorphic,coccobacillary bacteria
Obligatoryintracellular
Q fever Typhoid-likeillness
Almost worldwidedistribution
Reservoirs: wildanddomesticanimals Infectionresults frominhalationofaerosolscontainingtheorganism
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Coxiella burnetii
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Coxiella burnetii
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Laboratory Diagnosis
Demonstrationofspecific AbsComplement fixationtest
Indirectimmunofluorescenceassay
Isolationoforganism
Notrecommended
Treatment
Doxycycline
Control