Rickettsia   Dr Kamran AfzalAsst Prof Microbiology
Rickettsia• General characteristics  – Obligate intracellular organisms     • Intracellular location varies  – Rickettsiae...
Epidemiology• Transmission   – Maintained in arthropods like ticks, lice, fleas and     mites   – Usually transmitted to h...
Pathogenesis• Rickettsiae infect endothelial cells in small blood vessels   – Induced phagocytosis• Lysis of phagosome and...
Pathogenicity of RickettsiaBacteria infect                    Blockade of small  vascular                           blood ...
Immunity• Humoral and cell mediated immunity important for  recovery   – Antibody-opsonized bacteria are killed   – CMI de...
Clinical features• Early signs and symptoms   – History of arthropod vector bite   – Sudden fever, nausea, vomiting, sever...
• Later Signs and Symptoms   – Late (petechial) rash on     palms, forearms and trunk   – Abdominal pain, joint pains,    ...
Lab Diagnosis• Indirect immunoflourescence assay (IFA)• ELISA and latex agglutination   – Increased IgM titers by the end ...
IFA reaction of a positive human        Gimenez stain of tick             serum                   hemolymph cells infected...
Groups of RickettsiaeEpidemic typhus group R. prowazekii  Epidemic typhus                 South America                   ...
Epidemic Typhus Group
Epidemic Typhus Group• Epidemic typhus or louse-borne typhus   – Rickettsia prowazekii   – Lice• Endemic or Murine typhus ...
Epidemic Typhus (louse-borne typhus)• Rickettsia prowazekii• Carried by the human body louse• It grows in the GI of the lo...
• Laboratory Diagnosis (Rickettsia prowazekii)   – Weil-Felix antibodies - not recommended   – Isolation possible but dang...
• Treatment, Prevention and Control   – Tetracycline and chloramphenicol   – Vaccine available for high risk populations  ...
Endemic or Murine Typhus• Rickettsia typhi• Rodent is the host and is spread by fleas   – No transovarian transmission   –...
• Clinical Syndrome (Endemic or Murine typhus)   – Incubation period 1 - 2 weeks   – Sudden onset of fever, chills, headac...
• Laboratory Diagnosis   – Serology (R. typhi)      • Indirect fluorescent antibody test
• Treatment, Prevention and Control   – Tetracycline and chloramphenicol   – Control rodent reservoir
Scrub Typhus Group
Scrub Typhus• Orientia tsutsugamushi• Japanese “tsutsuga” = small and dangerous• “mushi” = creature• “Scrub” - associated ...
• Clinical Syndrome (Scrub Typhus)   – Incubation period - 1 to 3 weeks   – Sudden onset of fever, chills, headache and my...
• Treatment, Prevention and Control• Tetracycline and chloramphenicol• Measures to avoid exposure to chiggers
Spotted Fever Group
Rocky Mountain Spotted Fever
• Rocky Mountain Spotted Fever• Rickettsia rickettsii Fluorescent Ab staining         Vector - Tick
• Clinical diagnosis most important   – Most common in spring and summer   – More common in children <15 yrs   – 2-6 days ...
• Pathogenesis and Immunity   – No known toxins or immunopathology   – Destruction of cells      • Leakage of blood into t...
• Laboratory Diagnosis (R. rickettsii)   – Initial diagnosis - clinical grounds   – Fluorescent Ab test for Ag in punch bi...
• Treatment, Prevention and Control  – Tetracycline and chloramphenicol     • Prompt treatment reduces morbidity and morta...
35-years-old man                      3-days H/O fever + chills +                            headache + vomiting          ...
The owner of the rats had been in hospital       with hepato-renal failure
Ricketssia
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Ricketssia

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Ricketssia

  1. 1. Rickettsia Dr Kamran AfzalAsst Prof Microbiology
  2. 2. Rickettsia• General characteristics – Obligate intracellular organisms • Intracellular location varies – Rickettsiae replicate in cytoplasm • R. rickettsiae exception (replicate in nucleus) – Growth slow compared to bacteria – Small, cocco-bacillary bacteria
  3. 3. Epidemiology• Transmission – Maintained in arthropods like ticks, lice, fleas and mites – Usually transmitted to human by bite of vector• Organism passed vertically in insect vectors – Trans-ovarially • Louse-borne typhus exception • Louse dies of its infection and does not transmit the organism to its offspring – Human to human transmission via louse• Man is an incidental host
  4. 4. Pathogenesis• Rickettsiae infect endothelial cells in small blood vessels – Induced phagocytosis• Lysis of phagosome and entry into cytoplasm – Phospholipase• Replication• Release – Primary lesion is vasculitis
  5. 5. Pathogenicity of RickettsiaBacteria infect Blockade of small vascular blood vessels endothelium & skin rashesEnter cells by Vasculitis & endocytosis Thrombosis Multiply Infection of within cell other cells Release of Host cell lysis rickettsia
  6. 6. Immunity• Humoral and cell mediated immunity important for recovery – Antibody-opsonized bacteria are killed – CMI develops
  7. 7. Clinical features• Early signs and symptoms – History of arthropod vector bite – Sudden fever, nausea, vomiting, severe headache, muscle pain, lack of appetite – The rash first appears 2-5 days – Most often it begins as small, flat, pink, non-itchy spots (macules) on the wrists, forearms, and ankles – These spots turn pale when pressure is applied and eventually become raised on the skin – Skin rashes due to vasculitis
  8. 8. • Later Signs and Symptoms – Late (petechial) rash on palms, forearms and trunk – Abdominal pain, joint pains, diarrhea
  9. 9. Lab Diagnosis• Indirect immunoflourescence assay (IFA)• ELISA and latex agglutination – Increased IgM titers by the end of the first week of illness – IgG do not appear until 7-10 days after the onset – IgG antibodies are more specific and reliable • other bacterial infections can also cause elevations in riskettsial IgM antibody titers• PCR can detect DNA of 5-10 rickettsiae present in a sample, more specific than antibody-based methods
  10. 10. IFA reaction of a positive human Gimenez stain of tick serum hemolymph cells infected with on Rickettsia rickettsii grown in R. rickettsii chicken yolk sacs, 400X
  11. 11. Groups of RickettsiaeEpidemic typhus group R. prowazekii Epidemic typhus South America and Africa Recrudescent typhus Worldwide Sporadic typhus United States R. typhi Endemic Murine typhus WorldwideScrub typhus group O. tsutsugamushi Scrub typhus Asia, northern AustraliaSpotted fever group R. rickettsii Rocky Mountain spotted fever Western hemisphere R. akari Rickettsialpox USA, former USSR
  12. 12. Epidemic Typhus Group
  13. 13. Epidemic Typhus Group• Epidemic typhus or louse-borne typhus – Rickettsia prowazekii – Lice• Endemic or Murine typhus – Rickettsia typhi – Rat Fleas
  14. 14. Epidemic Typhus (louse-borne typhus)• Rickettsia prowazekii• Carried by the human body louse• It grows in the GI of the louse then enters as the feces of the louse enters the wound as you scratch the bite• Incubation period approximately 1 week• High fever lasting 2 weeks at least, followed by stupor and rash• Recovery may take months• High mortality if not treated• Complications – Myocarditis, stupor, delirium (Greek “typhos” = smoke)• Anne Frank died of Typhus
  15. 15. • Laboratory Diagnosis (Rickettsia prowazekii) – Weil-Felix antibodies - not recommended – Isolation possible but dangerous – Serology • Indirect fluorescent Ab • Latex agglutination tests
  16. 16. • Treatment, Prevention and Control – Tetracycline and chloramphenicol – Vaccine available for high risk populations – Louse control measures
  17. 17. Endemic or Murine Typhus• Rickettsia typhi• Rodent is the host and is spread by fleas – No transovarian transmission – Normal cycle - rat to flea to rat• Less severe than epidemic typhus – Similar symptoms and treatment• Mortality less than 5 percent
  18. 18. • Clinical Syndrome (Endemic or Murine typhus) – Incubation period 1 - 2 weeks – Sudden onset of fever, chills, headache and myalgia – Rash in most cases • Begins on trunk and spreads to extremities (centrifugal spread) – Mild disease - resolves even if untreated
  19. 19. • Laboratory Diagnosis – Serology (R. typhi) • Indirect fluorescent antibody test
  20. 20. • Treatment, Prevention and Control – Tetracycline and chloramphenicol – Control rodent reservoir
  21. 21. Scrub Typhus Group
  22. 22. Scrub Typhus• Orientia tsutsugamushi• Japanese “tsutsuga” = small and dangerous• “mushi” = creature• “Scrub” - associated with terrain with scrub vegetation• Vector - chiggers (mite larva)• Reservoir - chiggers and rats – Transovarian transmission – Normal cycle - rat to mite to rat• Humans are accidentally infected
  23. 23. • Clinical Syndrome (Scrub Typhus) – Incubation period - 1 to 3 weeks – Sudden onset of fever, chills, headache and myalgia – Maculo-papular rash • Begins on trunk and spreads to extremities (centrifugal spread) – Mortality rates variable
  24. 24. • Treatment, Prevention and Control• Tetracycline and chloramphenicol• Measures to avoid exposure to chiggers
  25. 25. Spotted Fever Group
  26. 26. Rocky Mountain Spotted Fever
  27. 27. • Rocky Mountain Spotted Fever• Rickettsia rickettsii Fluorescent Ab staining Vector - Tick
  28. 28. • Clinical diagnosis most important – Most common in spring and summer – More common in children <15 yrs – 2-6 days between tick bite and disease – Acute fever, headache, toxicity, myalgia, mental confusion – Rash especially on palms and soles which spreads to trunk (centripetal spread) – Different from scarlet fever • trunk to extremities (centrifugal spread)
  29. 29. • Pathogenesis and Immunity – No known toxins or immunopathology – Destruction of cells • Leakage of blood into tissues (rash) • Organ and tissue damage – Humoral and cell mediated immunity important for recovery
  30. 30. • Laboratory Diagnosis (R. rickettsii) – Initial diagnosis - clinical grounds – Fluorescent Ab test for Ag in punch biopsy – PCR based tests – Weil-Felix test - no longer recommended – Serology • Indirect fluorescent test for Ab • Latex agglutination test for Ab
  31. 31. • Treatment, Prevention and Control – Tetracycline and chloramphenicol • Prompt treatment reduces morbidity and mortality – No vaccine – Prevention of tick bites • protective clothing, insect repellents – Prompt removal of ticks
  32. 32. 35-years-old man 3-days H/O fever + chills + headache + vomiting 5 days ceftriaxone and anti- malarials - No response Recovered with doxycycline Multiple bitesRemoved multiple arthropods after jungle trips
  33. 33. The owner of the rats had been in hospital with hepato-renal failure

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