Bush typhus Chiggerosis First described by Chinese in 3 rd century Severe epidemics occurred during world war 2 particularly in the Oceania areas In Japan it is known as Shichito fever or ID: 1045344
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1. SCRUB TYPHUS
2. Scrub typhusBush typhusChiggerosis
3. First described by Chinese in 3rd centurySevere epidemics occurred during world war 2 particularly in the Oceania areasIn Japan it is known as Shichito fever or Hatsuka feverThey controlled infestation by clearing vegetation or use of DDT prophylaxisDeath by weapon : death by scrub 1: 5
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5. Endemic and remerging in eastern and southern asia, northern Austrelia, and islands of western Pacific and Indian oceanIn some areas >3% of the population is infected or reinfected each month
6. Tsutsugamushi triangle
7. Scrub typhus outbreaks have been occurred in Assam and West Bengal during second world warIn 2012 October to December 42 cases were diagnosed in JaipurIn 2020 5 killed in Nagaland in another outbreak
8. In Kerala first cases described in Thiruvananthapuram in 2000From then scattered cases were reported in Thiruvananthapuram and Malabar areasNo published report in central Kerala
9. Caused by Orientia tsutsugamushi(Rickettsia tsutsugamushi)It varies from Rickettsia species both genetically and in cell wall composition, it lacks lipopolysaccharideThe immunity by infection wanes over 1-3 years and organism exhibits remarkable antigenic diversity
10. O. tsutsugamushi is a gram-negative coccobacillusUnique in that it is released from infected cells by budding from the plasma membrane of host cells.May phagocytosed by adjacent cells while still coated with original host cell membraneThree varients Karp, Gilliam, Kato
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12. The reservoir and vector of scrub typhus are larval trombiculid mites of genus LeptotrombidiumLarval mites also known as chiggers maintain infection by transovarial transmissionIncubation period 6 to 21 days after bite of an infected chiggerKnown to be an Imported disease to western countries
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15. Life cycle
16. Zoonotic tetradMitesSmall mammalsScrubby vegetatinsWet seaseon
17. Clinical manifestationsAcute febrile illnessAssociated headache , anorexia and malaise in insidious casesTypical symptoms fever lasting long in untreated patients(9 to 19 days)Intense generalized headacheDiffuse myalgiaElder patients at risk of fatal outcomesDelay in therapy also associated with risk of complications
18. Triad EscharMaculopapular rashRegional lymphadenopathy
19. Eschar painless papule often appears at site of the infecting biteFollowed by central necrosis and black crust formationOne or multiple eschars can occurAtypical presentation a lack of black crust less than 50% of westerners develops eschar
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23. RashNonpruritic, macular or maculopapular rashBegins on the abdomen and spread to extrimitiesFace is often involvedRarely petechie developsLess than 40% of westerners develop rash at 4-6 days of illness
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25. LymphadenopathyLocalized, subsequent generalized lymphadenopathy accompanied by inflammation of lymphatic sinuses, splenomegaly and portal triaditis
26. complicaionsGastrointestinal nausea, vomiting , diarrhea ¼ th of patients 33 to 56 patents with GI symptoms had superficial ulcers, erosions or actively bleeding ulcers Upper GIT lesions associated with severity and cutaneous lesionsAcute kidney injury
27. Respiratory complaints occurred in 45% of population65% patients with respiratory symptoms had abnormal radiographsMost common radiographical abnormality were bilateral reticular opacitiesRelative bradycardia is commonPericardial effusion and myocardities can occur
28. Involvement of blood vessels in CNS produce meningitis, with mononuclear responseEncephalitis occurs rarelyAcute hearing loss or tinnitus occurred after being ill for more than one week
29. CNS involvment ranges from aseptic meningitis to frank meningoencephalitisAlso present as seizures, delirium Cerebellitis, myelitis and cerebral hemorrhages were also occurredCSF sows lymphocytic pleocytosis and raised protein
30. In pregnancy scrub typhus may cause spontaneous abortions or stillbirths Preterm birth , low birth weight can occur
31. diagnosisNo laboratary test is diagnostically reliable in the early phase of scrub typhusSevere illness pateints develops thrombocytopeniaElevation in hepatic enzymes , bilirubin and creatinineLeukopenia or leukocytosis can occur but usually normal count
32. 4 methods are used definitively confirm O tsutsugamushiSerologyBiopsyCulturePCR
33. SerologyIndirect fluorescent antibody(IFA) mainstay of serologic diagnosisELISA and passive hemoagglutination assay are also usedA dot blot immunoassay dipstick can be used for rapid diagnosisWeil Felix test is neither specific nor sensitive not used now a days
34. BIOPSYBiopsy of eschar or rashCharacteristic finding lymphohistiocytic vasculitisDamage to vascular endothelium occurs early in the coarse of infectionLeading to loss of vascular integrity, egress of plasma and plasma proteinsHistologically focal areas of cutaneous necrosis surrounded by zone of intense vasculitis with perivascular collections of lymphocytes and macrophages, this are diagnostic
35. CultureEgg(yolk sac), cell culture(vero cells MRC 5 cells ,L929 mouse fibroblast cells)Only available in specialized laboratory facilities
36. PCRCan definitivey establish diagnosisSensitivity of nested PCR 82% and specificity 100%In additional to serum PCR , eschar PCR can also be used
37. Differential diagnosisMalaria and dengue share same clinical and endemic patternsLeptospirosis, coinfaction occurs rarelyOther rickettsial diseases( R .austalis, R. sibirica) may mimic scrub typhus fortunately treatment is same Salmonella typhi in endemic areasAnthraxSpider bite
38. TreatmentChoice of agent Doxycycline( 100mg bd IV or oral for 7-15 days)Azithromycin an alternative agent(500mg for 3days)Chloramphenicol first effective treatment in endemic areas(500mg qid for 7-15 days)
39. In pregnancy azithromycin is safer to use Certain studies showed there was no difference in outcome in pregnant women treated with or without azithromycin
40. Certain strains of O tsutsugamushi are resistant or unresponsive to therapy with tetracyclinsIn such cases azithromycin or combination with rifamycin can be used
41. PreventionNo vaccine is available Current attempts at prevention consists of chemoprophylaxis and mite control
42. ChemoprophylaxisSeveral studies demonstrated that chemoprophylaxis with long acting tetracyclines are highly effective in non-immune individuals living or working in endemic areas
43. Mite controlDEET N,N-diethyl-3-methylbenzamide highly effective when applied to clothing and skinPermethrin and benzyl benzoate are used on clothing and beddingIn military camps lindane, dieldrin or chlordane are used
44. Intensive efforts at rodent control may paradoxically increase the risk of human disease.In such times , chiggers lose their preferred and normal hosts, there by biting more humans
45. Thank you……