Rickettsial Diseases

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Rickettsial Diseases
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General introduction

• Gram-negative, obligate intracellular
  coccobacilli bacteria that infect mammaols and
  arthropods
• Rickettsiae are transmitted in the
  arthropods,which serves as both vector and
  reservior
• Both DNA and RNA
• Is sensitive to antibiotic.

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Category of rickettsia

• Genus
• Rickettsia, Coxiella ,Orientia,Ehrlichia
  Bartonella
• Species
• Rickettsia prowazekii (epidemic typhus),
  Rickettsia typhi (endemic typhus), Rickettsia
  rickettsii (spotted fever), Rochalimaea quintana
  (trench fever), Coxiella burnetii (Q fever)

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Bilogical features

• Variable shape, coccobacilli
• Gram negative
• Microcapsule and slim layer
• Culture in york sacs of embryonated eggs

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Replication cycle of Rickettsia and Orientia
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Antigenic structure

• LPS
• Rickettsia tsutsugamushi
• Coxiella burnetii (Q fever)
• LPS? smooth
• LPS? rough
• Weil-Felix reacrion
• Surface protein(SPA)

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Transmission

• Typhus, spotted fever and trench fever are
  transmitted via arthropod vectors
• Q fever is acquired via inhalation or ingestion
  of contaminated milk or food.

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Pathogenesis

• Virulence factors endotoxin, phospholipase A,
  and slime layer
• Sites vascular system producing vasculitis???
• Characteristic triad of symptoms fever, headache
  and rash (no rash with Q fever).

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Rickettsia prowazekii??????

• epidemic typhus
• average incubation periods (days)8
• the louse
• Respiratory tract and conjunctiva
• Latent period 2 weeks
• Abrupt onset,fever,chills,headache,
• myalgia,arthralgia

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Rickettsia typhi???????????

• endemic typhus
• 7-14 days
• Mice
• the louseflea
• Mouth,nose and conjunctiva
• Gradual onset,fever,headache,myalgia,
• cough

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Rickettsia tsutsugamushi???????

• Tsutsugamushi disease(scrub typhus)
• Mice
• tsutsugamushi
• Black eachar??

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Coxiella burnetti?????

• Q fever
• Cow and sheep
• tick
• High resistance

abrupt onset ,fever,headache,chills,myalgia,granulomatous hepatitis
chronic diaease with subacute onset ,endocarditis,hepatic dysfunction
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Replication of C. burnetii
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Generalized Life Cycle of Dermacentor variabilis
and Dermacentor andersoni Ticks
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Bartonella henselae?????

• CSD (cat scratch disease)
• Cat and dog
• Conjunctiva inflammation and lymph node swell

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Ehrlichia?????

• Ehrlichia chaffeensis human monocytotropic
  ehrlichiosis
• Ehrlichia sennetsu human granulocytotropic
  ehrlichiosis

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Replication of Ehrlichia????
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Proposed life cycle for the agent of Human
Granulocytic Ehrlichiosis?????
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Diagnosis

• The use of immunofluorescent antibodies to
  examine a biopsy can be diagnostic.
• The organism can be inoculated into tissue
  culture and grown over 4-7 days but this is very
  hazardous to personnel.
• The Weil-Felix test looks for the production of
  serum antibody that is reactive against Proteus
  OX19, OX2 or OXK antigens but it is not always
  reliable.

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Control

• Sanitary Arthropod and rodent control
• Immunological No vaccines are currently
  available.
• Chemotherapeutic Tetracycline or chloramphenicol
  are drugs of choice.