1. SCRUB TYPHUS
Dr Prashant Makhija

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
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
Harrison’s Principles of Internal Medicine. 18th ed.Ch174

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”
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
Harrison’s Principles of Internal Medicine. 18th ed.Ch174

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
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005

5. Life cycle of Trombiculid mite

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
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005

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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Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34

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
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
Harrison’s Principles of Internal Medicine. 18th ed.Ch174

9. SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005

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
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
Harrison’s Principles of Internal Medicine. 18th ed.Ch174

11. Ann Indian Acad Neurol. 2012 Apr-Jun; 15(2): 141–144

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
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
Harrison’s Principles of Internal Medicine. 18th ed.Ch174

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%
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
Harrison’s Principles of Internal Medicine. 18th ed.Ch174

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

15.  Trigeminal neuralgia
 Brachial plexus neuropathy
 Guillain–Barre syndrome
 Cerebral infarction
 Acute disseminated encephalomyelitis
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
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34

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

22. THANK YOU