Orientia
It is garm negative bacilli adapted to
intracellular parasitism
 Transmitted by arthropod vectors
 There is only one human pathogen:
causes scrub typhus

ORIENTIA TSUTSUGAMUSH
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

History
1944 is the year which gain more attention
towards this disease
 US army`s 530 7th composite unit popularly
known as Merrill`s 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

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
Causes
Transmitted by some sps of trombiculid
mites
 Particularly Leptotrombidium deliense
 The bite of this mite leaves a characteristic
black eschar

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.

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
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

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