Orientia

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Orientia
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• It is garm negative bacilli adapted to
  intracellular parasitism
• Transmitted by arthropod vectors
• There is only one human pathogen
• causes scrub typhus
• ORIENTIA TSUTSUGAMUSH

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Scrub typhus

• Also kown as CHIGGER-BORNE TYPHUS
• It is transmitted by mites belonging to
  Leptotrombidium
• Human beings infected when they are bitten by
  mite larvae (chiggers)
• The mites feed on serum of
• worm blooded animals only
• once in their life
• Adults feed on plant juices

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History

• 1944 is the year which gain more attention
  towards this disease
• US armys 530 7th composite unit popularly known
  as Merrills Marauders lost half of their unit to
• this disease
• severe epidemics found
• in US troops stationed
• in JAPAN
• Soldiers used to call it
• shichito fever or hatsuka
• fever

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geographical distribution

• Endemic to a part of the world popularly known as
  tsutsugamushi triangle
• It extends from northern japan and far east
  russia in the north to northern australia in the
  south and pakistan and afghanistan in the west

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Causes

• Transmitted by some sps of trombiculid mites
• Particularly Leptotrombidium deliense
• The bite of this mite leaves a characteristic
• black eschar

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Symptoms and signs

• Signs macculopapular rash,
• eschar, splenomegaly,
• lymphadenopathies
• Symptoms fever, head ache
• muscle pain, cough,
• G.I symptoms.
• More virulent strains cause hemorrhage and
  intravascular coagulation.

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Laboratory findings

• Leucopenia,
• Abnormal liver function tests

Diagnosis

• In endemic areas clinical grounds are alone
  sufficient
• Cheapest and most easily available serological
  test is weil-felix test which is notoriously
  unreliable
• The golden standard is indirect
  immunofluorescence
• Rapid bedside kits are also available

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Treatment

• Without treatment disease often fatal
• Most commonly used drug is doxycyclin
• Alternate is chloramphenicol
• Rifampacin and azithromycin are alternative in
  resistant strains
• Azithromycin is the choice for children and
  pregnants

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Vaccines

• No licensed vaccines available
• An attempt to create a scrub typhus vaccine
  occurred in UK in 1937 under a classified project
  operation tyburn but the vaccine was not used
• First known type of scrub typhius vaccine
  actually used to inocculate in human subject was
  dispatched by ALFSEA in june 1945
• It was produced by weellcomes lab at sussex
• Scrub typhus shows anormous antigenic variation
  in its strains immunity to one strain does not
  confer immunity to other