2. INTRODUCTION
Rickettsiae- heterogeneous group of small, obligatory
intracellular, gram-negative coccobacilli and short bacilli,
transmitted by a tick, mite, flea, or louse vector
Typhus- Greek word ‘Typos’, for ‘fever with stupor’, caused by
rickettsial organisms that result in an acute febrile illness
Earliest medical accounts of typhus were written by Cardano in
1536 and Fracastroin 1546
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3. Scrub typhus- illness was described by Hashimoto in 1810
Ogata in 1931 isolated the organism and named it Rickettsia
tsutsugamushi, now reclassified as Orientia tsutsugamushi
Tsutsugamushi- “dangerous bug”
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4. ETIOPATHOGENESIS
Vector- larva of Trombiculid mite (berry bugs, harvest mites,
red bugs, scrub-itch mites )
Trans-ovarian transmission maintains the infection in nature
Mites have a four-stage lifecycle: egg, larva, nymph and adult
Chigger phase (Larval stage) is the only stage that is parasitic
on animals or humans
Larvae feed on small rodents particularly wild rats of subgenus
Rattus, Man gets infected accidentally
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6. Chiggers have grasped a passing host, insert their mouthparts
down hair follicles or pores
inject a liquid that dissolves the tissue around the feeding site
liquefied tissue is then sucked up as sustenance for the chigger
R.tsutsugamushi organisms are found in the salivary glands of
the chigger, they are injected into its host when it feeds
Bacterium is an intracellular organism living and breeding within
the cells of its host
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7. Organisms proliferate on the endothelium of small blood vessels
releasing cytokines which damage endothelial integrity, causing
fluid leakage, platelet aggregation, polymorphs and monocyte
proliferation
Focal occlusive end-angiitis causing microinfarcts- especially
affects skeletal muscles, skin, lungs, kidneys, brain and cardiac
muscles
Can also cause venous thrombosis and peripheral gangrene
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8. EPIDEMIOLOGY
An estimated one billion people are at risk for scrub typhus and
one million cases occur annually
Endemic in Asia and Pacific Islands- Asia, Australia, New
Guinea, Pacific Islands
Scrub typhus is known to occur all over India including the
hills of North India
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10. CLINICAL FEATURES
Illness varies from mild, self-limiting to fatal
Incubation period - 6-21 days
Onset & Initial clinical manifestations
fever, headache, myalgia, cough, gastrointestinal symptoms
a primary papular lesion(where the chigger has fed)
enlarges, undergoes central necrosis, and crusts to form a flat
black eschar
Associated regional and later generalized lymphadenopathy
and a macular rash may appear on the trunk
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12. CLINICAL FEATURES
Untreated self-limiting ds.- febrile for about 2 weeks and have a
long convalescence of 4 to 6 weeks thereafter
Fulminant course- complications usually develop after the first
week of illness
Complications
Neurological- meningoencephalitis
Pulmonary- interstitial pneumonia
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13. GI- superficial mucosal hemorrhage, multiple erosions, and ulcers
Cardiac- Myocarditis with conduction blocks & CCF
Septicemic shock with ARDS, DIC, with renal & hepatic
dysfunction
Mortality- 7-30%
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14. NEUROLOGICAL COMPLICATIONS
Most case series report Meningitis/meningoencephalitis as the
most common neurological complication of Scrub Typhus
Other reports of Neurological complications
Isolated abducens (VI) nerve palsy
Bilateral simultaneous facial nerve palsy in convalescent period
Scrub typhus associated with opsoclonus, transient Parkinsonism,
and myoclonus has been observed
Ann Indian Acad Neurol. 2013 Jan-Mar; 16(1): 131
16. Author
No of Pts
Neurological
features
Outcome
Vivekanandan et.al
(2004)
50
Meningitis-14%
Altered sensorium20%
Mortality-2%
Razak et.al(2004)
29
Meningoencephalitis
-20%
Cerebellar signs-3%
All improved
Mahajan et.al(2006)
27
Meningoencephalitis
-14.8%
Mortality-3.7%
Mahajan et.al(2010)
21
Seiures-19%
Altered sensorium23.8%
Mortality-14.2%
Chrispal et.al(2010)
189
Altered sensorium22.2%
Seizures-6.3%
Meningitis-20.6%
Mortality-12.2%
Ann Indian Acad Neurol. 2012 Apr-Jun; 15(2): 141–144
17. INVESTIGATIONS
Routine blood investigations
Hemogram- Leukopenia and thrombocytopenia
Coagulopathy
Elevation of liver enzymes and bilirubin - indicating
hepatocellular damage
↑ Creatinine, Proteinuria
Chest X-rays- Reticulonodular infiltrates
CSF examinations show a mild mononuclear pleocytosis with
normal glucose levels
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
18. Test
Comments
Weil Felix
Detects cross-reacting antibodies to Proteus mirabilis OXK
4-fold ↑ in titre to OXK
single titre ≥ 1:160 also diagnostic
Lacks sensitivity & specificity
ELISA
Detects Ab against infectious agents by using pooled human
sera
Higher sens. & spec.
Western Blot(KpKtGm)
Presence of a 41-kD band
Higher sens. & spec.
Indirect Fluorescent Assay
Conclusive diagnosis: 4-fold ↑ in IFAs in paired serum
obtained 2 wks apart
Currently considered gold standard
PCR amplification
most sensitive
Limited availability, expensive
Isolation
Can be isolated & cultured by inoculating intraperitoneally
into white mice
not used routinely
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
19. TREATMENT
Preventive
avoidance of the chiggers that transmit O. Tsutsugamushi
insect repellents and by the use of protective clothing impregnated
with benzyl benzoate
natural strains are highly heterogeneous, infection does not
complete protection against reinfection
Vaccines tried
short exposure, chemoprophylaxis with Doxycycline (200 mg
weekly) can prevent infection
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
20. Definitive therapy
therapeutic trial of tetracycline in suspected patients
Recommended regimen- Doxycycline (2.2 mg/kg/dose bid PO or
IV, maximum 200 mg/day for 7-15 days)
Alternative regimens :
Tetracycline- 25-50 mg/kg/day divided every 6 h PO, maximum
2 g/day
Chloramphenicol (50-100 mg/kg/day divided every 6 h IV,
maximum 3 g/24 h, or 500 mg qid orally for 7-15 days for adults
Azithromycin (500 mg orally for 3 days)
Rifampicin (600 to 900 mg/day)
Intensive care may be required for haemodynamic management of
severely affected individuals
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21. CONCLUSION
Scrub typhus is a growing and emerging disease grossly underdiagnosed due to its non-specific clinical presentation, limited
awareness, and low index of suspicion
Early diagnosis and treatment are imperative to reduce the
mortality and the complications associated with the disease