1. Scrub Typhus- case presentation
Dr. D.P.Bansal (M.D.,D.M.)
Dr. Mohd Viquasuddin Saim
DNB medicine resident
Medwin hospital

2. Case presentation
• An 18 year old female , resident of
Mahbubnagar district was admitted with
history of fever since 2 weeks, cough since 2
weeks, vomitings since 10 days, pain abdomen
and shortness of breath since 3 days
• Fever was continuous, high grade, subsiding
on medication and not associated with chills
• Cough was non productive

3. Case presentation
• Vomitings were 3 to 4 episodes/day, non
projectile, non bilious, associated with nausea
aggravated by food intake.
• pain abdomen was diffuse, intermittent,
colicky in nature, aggravated on food intake
and associated with constipation
• Shortness of breath was present at rest , not
asssociated with chest pain. There was no
orthopnea or PND.

4. Case presentation
• o/e :
• Conjunctival suffusion +
• Lungs : BAE +, b/l basal crepts +
• p/a : guarding +
• Heart sounds : normal
• CNS : NAD

5. Case presentation
• Evaluation of the patient revealed
• Anemia (Hb : 8.1)
• Thrombocytopenia (63,000)
• WBC : 7500
• Chest x ray : b/l diffuse haziness s/o
pneumonia
• Weil felix test was positive for OX-K antigen
• LFT’s were raised

6. Case presentation
• Dengue IgG and IgM were negative
• Dengue NS1 antigen was negative
• HBsAg, HAV, HCV, HIV I & II were negative
• Leptospira IgM was negative
• Blood culture did not reveal any bacterial
growth , WIDAL test was negative
• Smear for Malarial parasite and parasite F and
V were negative

7. Case presentation
• A diagnosis of scrub typhus was made and
patient was treated with Doxycyline, IVF,
antipyretics, and antiemetics.
• Daily platelet counts and liver parameters
were monitored.
• Patient improved symptomatically and was
discharged after 10 days.

8. Scrub typhus : historical background
• Also known as Japanese river fever
• ‘tsutsugamushi’ in japanese means tsutsuga =
disease, mushi = bug
• Disease was also endemic in south and
southeast asia
• Major infectious disease in asia during second
world war
• Scrub typhus research laboratory was
established in Imphal, India

9. epidemiology
• Important and widespread cause of febrile
illness in rural areas of asia
• Caused by Orientia tsutsugamushi ( formerly
Rickettsia tsutsugamushi )
• Contracted via the bite of the larval stage (
chigger) of trombiculid mite.
• Infected mites are characteristically found in
discrete foci called ‘mite islands’

10. epidemiology
• Mite islands can occur in a wide range of
vegetations types like :
• Scrub (tall-growing coarse grass)
• Forests
• Gardens, beaches
• Paddy fields
• Bamboo patches
• Oil palm or rubber estates

11. epidemiology
• O.tsutsugamushi is an obligate intracellular
bacterium
• Its maintained transovarially in mite
population and rodents
• Larval stages normally feed on rodents
• Humans are accidental hosts
• Recently a new species O.chuto has been
discovered in UAE

12. chigger

13. pathogenesis
• O. tsutsugamuhi infects endothelial cells,
macrophages and PMNs.
• Bacteria uses host fibronectin interactions
with its 56-kDA antigen (TSA56) for
attachment.
• Invades host cell via induced phagocytosis
• Enters phagosome and then escapes into
cytoplasm

14. pathogenesis
• Replicates via binary fission and then is released
covered by host cell membrane
• Recent evidence suggests pathophysiology of
o.tsutsugamushi is different from endothelium
targeting Spotted fever group.
• Mononuclear cell activation was more prominent
than endothelial cell activation
• Primary cytopathic destruction of endothelium of
blood vessels causing vasculitis

15. Clinical features
• Presents as a systemic vasculitic infection
• Most of the pathogenesis is unknown
• Symptoms occur between 6 to 10 days after
mite bite
• Typically presents with fever,
lymphadenopathy, macular-maculopapular
rash, severe headache and myalgia
• muscle tenderness is minimal or absent

16. Clinical features
• Also seen are
• Nausea and vomiting
• Diarrhea
• Constipation
• Conjunctival suffusion
• Reversible sensorineural deafness

17. Clinical features
• A painless papule occurs at the site of the bite
prior to the onset of disease symptoms
• This painless papule later ulcerates and
transforms into a black crust or ‘eschar’ in
variable proportion of patients
• eschar is not noticed in all patients because of
variability in thoroughness of physical
examinations and immunological factors

18. Eschar

19. complications
• Jaundice
• Meningoencephalitis
• Myocarditis
• Interstitial pneumonia leading to ARDS
• Renal failure
• Mortality was 42 % in preantibiotic era
• Mortality still high in rural areas

20. Immunity
• Remarkably short lived
• Lasts only a few months
• Highly strain specific
• Insufficient to protect from infection with
other strains

21. diagnosis
• Gold standard diagnostic tests are
• Immunofluorescent assay (IFA) and indirect
immunoperoxidase test (IIP) based on cell-culture
derived O.tsutsugamushi antigens
• These antigens are applied to paired
admission and convalescent samples
• These are not standardized and are usually
unavailable in poor tropical areas

22. diagnosis
• WEIL-FELIX test
• This test was developed in 1916 for typhus fever
• This is based on positive agglutination of Proteus
vulgaris (OX19) by the serum from patients with
all forms of typhus except scrub typhus
• In 1924, Dr. AN Kingsbury unknowingly
introduced a strain of Proteus mirabilis in malaya
where scrub typhus is endemic and strong
agglutinations were seen

23. diagnosis
• WEIL-FELIX test
• The antigen was termed as OXK (K=Kingsbury)
• The discovery of this antigen led to the
identification of two different types of typhus
fevers (scrub typhus and murine typhus)
• Sensitivity and specificity is low
• its predictive value can be increased by testing
both acute and convalescent phase samples
and observing rise in antibody titre

24. diagnosis
• WEIL-FELIX test
• low sensitivity means it gives high percentage
of false negative results.
• common in case of Scrub Typhus.
• low specificity meaning false positive results
are obtained in leptospirosis, and relapsing
fever , Proteus infections, brucellosis and
acute febrile illness

25. Diagnosis
• Anti-O.tsutsugamushi IgM and IgG based rapid
diagnostic tests have been developed but
evaluation is pending
• ELISA also can be used
• Benefits of ELISA include multiple tests at one
time, inexpensive, sensitive, specific.
• PCR methods have also been developed
• Target genes are 47 Kda, groEL genes

26. diagnosis
• Can be cultured from blood
• takes several weeks
• Special tissue culture techniques
• A bioSafety level 3 facility is mandatory
• Samples taken from eschars can be used for
both PCR-based or immunohistochemical
diagnosis due to high bacterial loads

27. Differential diagnosis
• Typhus : distinguished only be serological tests
• Malaria : by stained blood films
• Arbovirus infections : by serological methods
• Leptospirosis : by PCR or culture
• Relapsing fever : by blood smear, serology
• Meningococcal disease : by blood and CSF
cultures
• Typhoid : blood and bone marrow cultures
• Viral fevers

28. treatment
• It is very responsive to treatment
• Appropriate antibiotics should be given
empirically if the diagnosis is suspected
• D.O.C is Doxycycline if there are no
contraindications
• Adult oral dose of 100mg twice daily for 7
days
• Tetracycline 500mg every 6 hours for 7 days
can also be used

29. treatment
• Azithromycin (1000-500mg) on the first day
followed by 500-250mg daily for 2 days is an
effective alternative
• Azithromycin has also been shown to be
effective in single dose
• Azithromycin is particularly useful in
pregnancy where tetracyclines are
contraindicated

30. treatment
• Chloramphenicol is an alternative to the
tetracyclines (500 mg every 6 hours in adults
or 50-75 mg/kg per day in children for 7 days)
• Other antibiotics which have been used
successfully are Roxithromycin, telithromycin
and Rifampicin
• Fluoroquinolones have been assocaited with
treatment failures and should not be used.

31. prevention
• Preventive measures include :
• Wearing protective clothing
• Treatment of clothing with repellants or
acaricides
• Application of DEET to exposed skin
• No protective vaccine is available

32. -----------------
• Thank you