Ricketssiaceae

Rickettsia, Q Fever, Typhus

1. Rickettsiaceae Dr.M.Malathi Postgraduate Department of Microbiology Chengalpattu Medical College

2. Synopsis Genus Rickettsia Genus O rientia Genus Ehrlichia ---------------------------------------------------------------- Genus Coxiella Genus Bartonella

3. Introduction Intracellular growth Transmitted by blood sucking arthropod vectors Howard Taylor ricketts (1906) – Discovered spotted fever rickettsia – died of typhus fever contracted during his studies

4. Characteristics Small GNB Virus like , cannot be seen under ordinary light microscope Obligate intracellular parasite

5. Genus Rickettsia

6. TYPHUS FEVER GROUP Epidemic typhus Recrudescent typhus (Brill Zinsser disease) Endemic typhus

7. Epidemic typhus Causative agent: R.prowazekii V ertebrate host : Humans Human body louse : Pediculus humanus corporis

8. Lice

9. Pathogenesis: Lice become infected by feeding on ricketssiaemic patients  multiply in the gut of lice  appear in feces in 3 to 5 days  infection transmitted from person to person When the contaminated louse feces is rubbed through the minute abrasions caused by scratching Occasionally by aersols of dried louse feces through inhalation or through the conjuctiva

10. Incubation period is 5 to 15 days Fever with chills Characteristic rash – 4 th or 5 th day Stuporous and delirious Case fatality – 40%

11. Eschar

12. Recrudescent typhus Latent infection in whom recovered from epidemic typhus Reactivation Hence no extrahuman reservoir

13. Endemic typhus Causative agent: R. typhi Host: Rats, Humans Vector: Flea – Xenopsylla cheopsis Pathogenesis: Rickettsia multiplies in the gut of the flea  shed in faeces  humans

14. Flea

15. Humans acquire the disease: The bite of infected fleas, when their saliva or feces is rubbed in Through aerosols of dried feces By ingesting food recently contaminated with infected rat urine or flea feces Human infection is a dead end PERSON TO PERSON TRANSMISSION DOES NOT OCCUR

16. SPOTTED FEVER GROUP Common soluble antigen Multiply in the nucleus as well as in the cytoplasm of host cells All transmitted by ticks except R.akari (Mite borne) Tick typhus Rickettsial pox

17. Tick typhus Transovarian transmission – in ticks – both vector and reservoir Larval stage or adult ticks – infective form to vertebrate hosts Transmitted to human by tick bite

18. Tick

19. Rocky mountain spotted fever – most serious type Causative agent : R.rickettsii Indian tick typhus – R.conori Tick: Rhipicephalus sanguineus

20. Rickettsial pox Self limited, non fatal, vesicular exanthem Similar to chicken pox Vesicular or varicelliform rickettsiosis Causative agent: R.akari Reservoir : D omestic mouse Vector : mite ( Transovarial transmission)

21. Pathogenesis in humans Transmitted to humans by arthropod vectors through bite or feces Ricketssaie multiply locally and enter the blood Localised chiefly in the vascular endothelial cells  thrombus formation  occlusion of vascular lumen

22. Clinical features : acute febrile illness, septicemia with maculopapular rash and fever The long survival of rickettsiae in various organs and lymphatic tissues in infected humans and animals is a distinctive feature in its pathogenesis.

23. Specimen Smears from infected tissues Blood

24. Morphology Pleomorphic coccobacilli Non motile , non capsulated 0.3 – 0.6 * 0.8 – 2 um Gram negative, but do not stain well Under electron microscope  three layered cell wall

25. cultivation Unable to grow in cell free media Growth occurs in the cytoplasm of infected cells Optimum temperature – 32 to 35deg C Cultivated in yolk sac of developing chick embryos, also grow on HeLa , Hep-2, Detroit 6 continuous cell lines

26. Resistance Rapidly destroyed at 56degC Destroyed at room temp also Hence when seperated from host  preserve in skimmed milk or a suspending medium containing sucrose, potassium phosphate and glutamate (SPG medium)

27. Antigenic structure Spotted fever rickettsiae  A, B proteins Third surface antigen  alkali stable polysaccharide  found in some rickettsiae and in some strains of the Proteus bacilli

28. Who am i ?

29. Neil Mooser Reaction R.typhi and R.prowazekii – similar When male guinea pigs are inoculated intraperitoneally with blood from a case of endemic typhus or with a culture of R.typhi  develop fever and characteristic scrotal inflammation. Scrotum enlarged and testes cannot be pushed back into the abdomen because of inflammatory adhesions between the layers of the tunica vaginalis Neil – Mooser or tunica reaction

30. Genus Orientia

31. GENUS ORIENTIA SCRUB TYPHUS (CHIGGER BORNE TYPHUS): Causative agent: Orientia tsutsugamushi First observed in Japan Vector: trombiculid mites Mite islands Humans bitten by mite larvae (Chiggers) Transovarian transmission in mites

32. Trombiculid mite

33. Zoonotic tetrad  O.tsutsugamushi , chiggers, rats and secondary and transitional forms of vegetation Incubation period – 1 to 3 weeks Characteristic Eschar , regional lymphadenopathy and maculopapular rash Three antigenic types : Karp, Gilliam and Kato

34. Genus Ehrlichia

35. GENUS EHRLICHIA Small, Gram negative, obligate intracellular bacteria Tick borne Cytoplasm of infected phagocytic cells  grow within phagosomes as mulberry like clusters  Morula

36. Pathogenicity : Three infections Resembles glandular fever. Causative agent is Ehrlichia sennetsu . Endemic in Japan. Causes lymphoid hyperplasia and atypical lymphocytosis . No arthropod vector. Human infection is suspected to be caused by ingestion of fish with flukes

37. 2. Human monocytic ehrlichiosis – caused by Ehrlichia chaffeensis . Transmitted by Amblyomma ticks. Deer and rodents are reservoir hosts. Human disease with leukopenia , thrombocytopenia and elevated liver enzymes

38. 3. Human granulocytic ehrlichiosis – either identical with or closely related to equine pathogen Ehrlichia equi . Transmitted by ticks. Deer, cattle and sheep are the suspected reservoir. Leucopenia and thrombocytopenia are seen in patients Treatment: Doxycline for ehrlichiosis

39. LABORATORY DIAGNOSIS OF RICKETTSIAL DISEASES

40. Specimens Blood for culture Tissue for culture Serum for serological tests

41. Direct Microscopy Light microscope  cant see individual organism, only aggregations of rickettsial particles Giemsa stain  purple coloured basophilic inclusions Machiavello stain  red coloured inclusions Immunofluorescence microscope  skin biopsies from the centre of the petechial lesions

42. Culture Yolk sac of embryonated hen`s eggs Male guinea pigs or mice Tissue culture

43. Serological test Weil felix reaction : Agglutination test in which sera are tested for agglutinins to the O antigens of certain non motile Proteus strains OX 19, OX2, OX K Due to sharing of antigen by ricketssiae and certain strain of proteus Tube agglutination test

44. Other serological tests Complement fixation test ELISA RIA

45. Molecular methods Polymerase chain reaction

46. TREATMENT Tetracycline Chloramphenicol Ciprofloxacin

47. Genus Coxiella

48. GENUS COXIELLA Coxiella burnetii Causative agent of Q fever ( Query) Pleomorphic bacilli Obligate intracellular pathogen Differs from rickettsia by being More resistant to heat No vector

49. ? ? ?

50. Weil felix test cannot be used to diagnose Infection is from cattle , sheep and goats Zoonotic disease Bandicoot are the reservoir Transmitted to cattle by ixodid ticks Shed in milk of infected animals and transmitted to humans

51. Pathogenicity Human disease characterised by interstitial pneumonia Coxiella may remain latent in the tissues of patients of 2 to 3 years

52. Laboratory diagnosis Blood for microscopy Culture and serum for serological test PCR

53. Treatment Tetracycline Macrolide antibiotics

54. Genus Bartonella

55. GENUS BARTONELLA Tiny GNB Transmitted by arthropods Pathogenic strains B.bacilliformis B.quintana B.henselae

56. Bartonella bacilliformis Oroya fever High mortality Late sequel  verruga peruana 1885 – Medical student  Daniel Carrion  inoculated himself with material from verruga and developed oroya fever and died Carrion`s disease

57. Bartonella quintana First world war  trench fever or five day fever (Million of cases) No animal reservoir Transmitted by body louse Ability to grow in blood agar

58. Bartonella henselae Febrile illness with lymphadenopathy following a cat scratch  Cat scratch disease Isolated from the blood of patients in blood media after prolonged incubation Demonstrated in lymph node biospy smears and sections by Warthin -Starry staining

59. Associated with HIV infected and immunodeficient personns Bacillary angiomatosis

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