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Scrub typhus


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Scrub typhus

Scrub typhus

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  • 2. • Scrub typhus or Bushtyphus is a form oftyphus caused by theintracellular parasiteOrientia tsutsugamushi,a Gram-negative α-proteobacterium offamily Rickettsiaceaefirst isolated andidentified in 1930 inJapanSCRUB TYPHUSDR.T.V.RAO MD 2
  • 3. DR.T.V.RAO MD 3
  • 4. INCIDENCE OF SCRUB TYPHUS• The precise incidence of the disease is unknown, asdiagnostic facilities are not available in much of itslarge native range which spans vast regions ofequatorial jungle to the sub-tropics. In rural Thailandand in Laos, murine and scrub typhus accounts foraround a quarter of all adults presenting to hospital withfever and negative blood cultures The incidence inJapan has fallen over the past few decades, probablydue to land development driven decreasing exposure,and many prefectures report fewer than 50 cases peryear.DR.T.V.RAO MD 4
  • 5. SCRUB TYPHUS• Scrub typhus caused by Orientia tsutsugamushi• Mild to fatal• 6-18 days after bite of Mite• An Escher is formed at the site of bite• With enlargement of Lymph nodes, Interstitialpneumonitis ,lymphadenopathy,spleenomegalyEncephalitis, Respiratory failure, circulatoryfailureDR.T.V.RAO MD 5
  • 6. RICKETTSIA TSUTSUGAMUSHI.• Causative agent is Rickettsiatsutsugamushi. Found in areas wherethey harbour the infected chiggersparticularly areas of heavy scrubvegetations.DR.T.V.RAO MD 6
  • 7. • RESERVOIR: Trombiculid mite which feeds on smallmammals.MODE OF TRANSMISSION: By bite of infected larval mites.Infection occurs during wet season when the mites lay theireggs. It is the larva (chigger) that feeds on vertebrate hosts.TRANSMISSION CYCLEMITE------RATS AND MICE-----MITE----RATS AND MICEMANDR.T.V.RAO MD 7
  • 8. SCRUB TYPHUSEtiology: Orientia tsutsugamushiResembles Epidemic typhus except for theESCHARgeneralized lymphadenopathy & lymphocytosis• cardiac & cerebral involvement may be severeDR.T.V.RAO MD 8
  • 9. EPIDEMIOLOGY Source of infection--------Rat Route of transmission-----Trombiculid mites Susceptible population----All susceptible Epidemic features----------TsutsugamushitriangleDR.T.V.RAO MD 9
  • 10. DR.T.V.RAO MD 10
  • 11. MODE OF TRANSMISSIONMiteRats & MiceHumansMiteNo direct person to person transmissionMite Islands(Accidental host)DR.T.V.RAO MD 11
  • 12. CHIGGERreservoirLarval stagevectorDR.T.V.RAO MD 12
  • 13. An important vector-borne disease, firstdescribed in 1899 in Japan.During World War II, this disease killedthousands of soldiers who were stationedin rural or jungle areas of the Pacifictheatre.Scrub TyphusThe disease occurred and threatened people throughoutAsia & Australia. The range stretches from the Far-eastto the Middle-east (from Japan and Korea, Southeast Asia, Pakistan,India, to Arab countries and Turkey). There are approx. 1 millioncases each year world-wide, & over 1 billion people atrisk.DR.T.V.RAO MD 13
  • 14. CLINICAL FEATURES Incubation period: 1-3 wks. (usually6-21 days) Fever(104-105 F) with chills,malaise,conjunctivalIrritation. Maculopapular rash Lymphadenopathy,Lymphocytosis Headache, Cough, Myalgia Gastrointestinal symptoms Typical “Eschar formation”(5th day of illness)DR.T.V.RAO MD 14
  • 15. DR.T.V.RAO MD 15
  • 16. Pathogen: Orientia tsutsugamushiRickettsial bacteriaVector: LeptotrombidiumChigger-MiteAn acute febrile, rickettsial diseasecaused by a gram-negative, rod-shaped (cocco-bacillus) bacterium,known as Orientia (Rickettsia)tsutsugamushi.Scrub Typhus: A Rickettsial DiseaseO. tsutsugamushi is transmitted to vertebratehosts (rodents-primary host & humans-secondary or accidental host) by the bite of larvalmites (chiggers) of the genus Leptotrombidium, e.g. L. deliense, L. dimphalum, etc.DR.T.V.RAO MD 16
  • 18. EscharProbability: Higher than 60%.Location: Axillary fossa, inguinal region,perianal region, scrotum, buttocks and thethigh.Appearance: an ulcer surrounded by a redareola, is often covered by a dark scab.The most specific manifestation of scrub typhus.DR.T.V.RAO MD 18
  • 19. CLINICAL MANIFESTATION• Incubation period is 4~21• Sudden onset with a fever• 1st week, systemic toxic symptoms• 2nd week, get worse, complication• 3th week, convalesceDR.T.V.RAO MD 19
  • 20. COMPLICATIONS Pneumonitis Hepatitis Myocarditis Meningoencephalitis Disseminated intravascular coagulation Multi organ failureDR.T.V.RAO MD 20
  • 21. EscharProbability: Higher than 60%.Location: Axillary fossa, inguinal region,perianal region, scrotum, buttocks and thethigh.Appearance: an ulcer surrounded by a redareola, is often covered by a dark scab.The most specific manifestation of scrub typhus.DR.T.V.RAO MD 21
  • 22. INVESTIGATIONS• Weil-feilx test positive-proteus strain oxk• Indirect immunofluorescence.• PCR for Orientia tsutsugamushi fromblood of feverish patients.• Some studies have used PCR (polymerase chainreaction) on specimens obtained from eschars.DR.T.V.RAO MD 22
  • 23. DIAGNOSIS OF SCRUB TYPHUS• The cheapest and most easily available serological testis the Weil-Felix test, but this is notoriously unreliable.The gold standard is indirect immunofluorescence, butthe main limitation of this method is the availability offluorescent microscopes, which are not often availablein resource-poor settings where scrub typhus isendemic. Indirect immunoperoxidase (IIP) is amodification of the standard IFA method that can beused with a light microscope, and the results of thesetests are comparable to those from IFA.DR.T.V.RAO MD 23
  • 24. MANAGEMENT• Drug of choice: TetracyclineDoxycycline orally or Chloramphenicolin more severe cases.Azithromycin has been used inresistant cases and may be better thandoxycycline - especially in childrenand pregnant women.DR.T.V.RAO MD 24
  • 25. TREATMENT• The drug most commonly used is doxycycline; butchloramphenicol is an alternative. Strains that are resistantto doxycycline and to chloramphenicol are common innorthern Thailand.Rifampin and azithromycin arealternatives. Azithromycin is an alternative in children andpregnant women with scrub typhus, and when doxycycline-resistance is suspected. Ciprofloxacin cannot be usedsafely in pregnancy and is associated with stillbirths andmiscarriage. Combination therapy with doxycycline andrifampicin is not recommended due to possible antagonism.DR.T.V.RAO MD 25
  • 26. PREVENTIONVector control: Application of insecticides eg:lindane or chlordane to groundand vegetation. Environmental control Personal protectionDR.T.V.RAO MD 26
  • 27. • Programme Created by Dr.T.V.Rao MDfor Medical and Paramedical Studentsin the Developing World• Email• doctortvrao@gmail.comDR.T.V.RAO MD 27