This document discusses scrub typhus, caused by the bacteria Orientia tsutsugamushi, which is transmitted by the larval form of the trombiculid mite. Key points include: - Scrub typhus occurs in parts of Asia and the Western Pacific and has a mortality rate of 10-60% if untreated. - The bacteria are transmitted via the bites of larval mites (chiggers) that feed on rodents and birds, which act as reservoirs. - Clinical features include a necrotic skin lesion (eschar) at the bite site, fever, rash, and potentially severe complications like pneumonia or encephalitis. - Diagnosis involves

1. ( CHIGGER BORNE TYPHUS)
SCRUB TYPHUS
1CHIGGER

2. Scrub typhus-MICRO MGMC&H, Jaipur
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RICKETTSIACEAE
RICKETTSIA
R.prowazekii
R.typhi
R.rickettsii
R.conori
R.australis
R.siberica
R.akari
ORIENTIA O.tsutsugamushi
FAMILY GENUS SPECIES DISEASE
• True bacteria
• Obligate intracellular
parasite
Mostly by ticks
mites
Epidemic typhus
Brill-Zinsser disease
Endemic typhus
Rocky-mountain
spotted fever
Boutonneuse
fever
Australian
tick typhus
Siberian tick
typhus
Rickettsial
pox
Scrub typhus

3. INTRODUCTION-
 Caused by O.tsutsugamushi
“tsutsuga”-dangerous “mushi”-mite
 Occurs in Japan, Sumatra, Australia and islands
along the Western Pacific coast.
 Disease transmitted by- larval form of Mite
(Trombicula deliensis)
 Incubation period-7-10 days
 Case fatality-10-60%
Scrub typhus-MICRO MGMC&H, Jaipur
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O.tsutsugamushi

4. INFECTION-
 Larval form is known as chiggers.
 Found in areas of suitable climate, plenty of
moisture and scrub vegetation.
 Microbes are transmitted transovarianlly in all
mites.
 Various rodents and birds also act as
reservoirs.
Scrub typhus-MICRO MGMC&H, Jaipur
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CHIGGER

5. Scrub typhus-MICRO MGMC&H, Jaipur
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Four factors are
essential for the
establishment of
infection, namely, co-
existence and intimate
relationship among-

6. CLINICAL FEATURES-
 A necrotic lesion (eschar) occurs at the
site of bite in the skin.
 Severe headache
 Chills
 Fever
 Conjunctivitis
 Maculopapular rash
 Enlarged spleen and lymph nodes
 Severe cases –encephalitis and
pneumonia
Scrub typhus-MICRO MGMC&H, Jaipur
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MACULOPAPULAR RASH
ESCHAR

7. LABORATORY
DIAGNOSIS
• SPECIMENS
• DIRECT MICROSCOPY
• CULTURE (ISOLATION OF ORGANISM)
• SEROLOGY
• MOLECULAR METHODS
Scrub typhus-MICRO MGMC&H, Jaipur
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8. PRE REQUISITE -
They are highly infectious, their isolation should be attempted only in labs
equipped with appropriate safety measures.
UNABLE TO GROW ON CELL FREE MEDIA.
Scrub typhus-MICRO MGMC&H, Jaipur
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9. SPECIMENS-
For culture-
 Blood
 Tissue
For serological test
 serum
Scrub typhus-MICRO MGMC&H, Jaipur
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10. DIRECT MICROSCOPY
GIEMSA STAIN
 Purple colored basophilic inclusions
MACHIAVELLO’S STAIN
 Red colored inclusions
Scrub typhus-MICRO MGMC&H, Jaipur
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11. ISOLATION -
Scrub typhus-MICRO MGMC&H, Jaipur
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Blood clot in skimmed milk is inoculated
intraperitoneally in male mice.
Animals are to be observed for 3-4
weeks. Temperatures are recorded
daily.
RESULT- animal becomes ill and
develop ASCITIS.

12. Demonstration-
 Smears are taken from peritoneum, tunica and spleen of
infected animals.
 Stained by- GIEMSA STAIN
 Culture used- 1. YOLK SAC OF CHICK EMBRYO
2. TISSUE CULTURE
3. Vero and MRC5 CELL CULTURES
(not suitable for primary inoculation)
 Identified by- IMMUNOFLUOESCENCE TEST
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TISSUE CULTURE

13. SEROLOGY
Weil felix test
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Others-
• Compliment fixation test
• Latex agglutination test
• Enzyme immune assay

14. Weil-Felix Test
 Developed by Weil and Felix in 1916.
 Some Proteus (OX19, OX2, OXK) strains are agglutinated by sera of patients
with rickettsial infections.
 This is due to the antigenic sharing between species of proteus and
rickettsia.
 It is an eg. of heterophile agglutination test.
Scrub typhus-MICRO MGMC&H, Jaipur
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DISEASE
AGGLUTINATION WITH PROTEUS STRAIN
OX19 OX2 OXK
Scrub typhus - - +++

15. Scrub typhus-MICRO MGMC&H, Jaipur
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Tetracyclines and chloramphenicol
General measures-
Control of vectors and
animal reservoir.
Vaccination-
There is no safe and
effective vaccine.

16. THANK YOU
BY-
UMANG JUNEJA
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