SCRUB TYPHUS
Dr Prashant Makhija
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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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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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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Life cycle of Trombiculid mite
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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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
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
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
SK Mahajan. JAPI .VOL. 53. NOVEMBER 2005
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
Ann Indian Acad Neurol. 2012 Apr-Jun; 15(2): 141–144
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
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
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
Trigeminal neuralgia
Brachial plexus neuropathy
Guillain–Barre syndrome
Cerebral infarction
Acute disseminated encephalomyelitis
Ann Indian Acad Neurol. 2013 Jan-Mar; 16(1): 131
Ann Indian Acad Neurol. 2012 Apr-Jun; 15(2): 141–144
Author No of Pts Neurological features
Outcome
Vivekanandan et.al (2004)
50 Meningitis-14%Altered sensorium-
20%
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 sensorium-
23.8%
Mortality-14.2%
Chrispal et.al(2010) 189 Altered sensorium-22.2%
Seizures-6.3%Meningitis-20.6%
Mortality-12.2%
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
Rapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
Test Comments
Weil Felix Detects cross-reacting antibodies to Proteus mirabilis OXK 4-fold ↑ in titre to OXK single titre ≥ 1:160 also diagnosticLacks sensitivity & specificity
ELISA Detects Ab against infectious agents by using pooled human seraHigher 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 sensitiveLimited availability, expensive
Isolation Can be isolated & cultured by inoculating intraperitoneally into white mice not used routinely
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
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 individualsRapsang AG, Bhattacharyya P. Scrub typhus. Indian J Anaesth 2013;57:127-34
CONCLUSION
Scrub typhus is a growing and emerging disease grossly under-diagnosed 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
THANK YOU
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