1. Rickettsiae

2. Do not confuse with Rickets
Being human
Vitamin D or calcium deficiency that leads to soft bones

3. Rickettsiae Small gram negative Intracellular bacteria
Primary parasites found in the alimentary canal of arthropods-transmitted to humans by Lice/ flies /ticks and mites
In humans – infect vascular endothelium and Reticuloendothelial cells
Rickettsia named after HOWARD TAYLOR RICKETTS died of Typhus fever contracted during his studies
Discovered spotted fever rickettsia (1906)

4. HOWARD TAYLOR RICKETTS

5. MORPHOLOGY
In smears from infected tissues,rickettsiae appear as pleomorphic gram negative coccobacilli
Non motile non capsulated
They stain bluish purple with Giemsa and Castaneda stains
Unable to grow in cell free media
Growth generally occurs in the cytoplasm of infected cells

6. CULTIVATION PCR test Immunohistochemical detection Culture isolation
They are readily cultivated in the yolk sac of developing chick embryo
They also grow on mouse fibroblast,HeLa,Hep2,Detroit-6 and other continuous cell lines but tissue cultures are not satisfactory for primary isolation
Guinea pigs and mice are useful for the isolation of rickettsiae from patients
PCR test
Also possible with blood sample
Immunohistochemical detection
Culture isolation

7. Replication of Rickettsia and Orientia
Infect endothelial cells in small blood vessels - Induced phagocytosis
Lysis of phagosome and entry into cytoplasm - produce phospholipase
Replication
Release

8. RESISTANCE
Rickettsiae are readily inactivated by physical and chemical agents
They are rapidly destroyed at 560 C and at RT when separated from host components.
They can be preserved in skimmed milk or a suspending medium containing sucrose, potassium phosphate and glutamate(SPG medium)

10. Rash of Rocky Mountain Spotted Fever rash

11. Laboratory Diagnosis - R. rickettsii
Initial diagnosis - clinical grounds (important to begin treatment)
Fluorescent Ab test for Ag in punch biopsy - reference labs
PCR based tests - reference labs
Weil-Felix test - agglutination of O antigen of some rickettsial species is no longer recommended because it is not sensitive or specific
Serology
Indirect fluorescent Ab test for Ab
Latex agglutination test for Ab

12. Treatment, Prevention, and Control R. rickettsii
Tetracycline (doxycycline) and chloramphenicol (relapse and side effects)
Prompt treatment reduces morbidity and mortality
No vaccine
Prevention of tick bites (protective clothing, insect repellents)
Prompt removal of ticks
Can’t control the reservoir

13. Consequences of Delayed Diagnosis of RMSF
In Oklahoma on July 7 a 6 year-old presented with 1-day history of fever, headache, myalgia, and a macular rash on the arms, legs, palms, and soles
On July 1 a tick had been removed from the patients neck
Diagnosis: Viral illness; patient given oral cephalosporin
On July 11 the patient was hospitalized with dehydration, irritability, confusion, and thrombocytopenia
On July patient developed disseminated intravascular coagulation and iv doxycycline was administered.
The patient subsequently developed gangrene, requiring limb amputation and removal of the upper stomach and distal esophagus
August 19 the patient died.
Serum samples from July 12 and August 3 tested positive for antibodies to R. rickettsii

14. Rickettsiae Family- Rickettsiae-three genera Former members excluded
Orientia
Ehrlichia
Former members excluded
Coxiella burnetti- Q fever
Not athropod born
Rochalimaea quintana
Not an obligate intracellular parasite

15. Rickettsiae Genus reckettsia Typhus fever group
Epidemic typhus –R. prowazekii
Endemic typhus – R.typhi

16. Spotted fever group
Tick borne ⁄mite borne
R. ricketsii-rocky mountain spotted fever
R. siberica-siberian tick typhus
R. conori -indian tick typhus
R. australis –Queensland tick typhus
R. japonica- oriental spotted fever
R. akari –Ricketsial pox

17. Rickettsiae Genus orientia Genus Ehrlichia
Orientia tsutsugamushi – Scrub typhus
Genus Ehrlichia
E. sennetsu-Ehrlichiosis resembling glandular fever
E.chaffeenis – Human monocytic Ehrlichiosis
E. equi- Human granulocytic Ehrlichiosis

18. Rickettsiae Genus Coxiella Coxiellla burnetti- Q fever
Genus Bartonella
B. bacilliformis – verruga peruvana
Oroya fever /Carrion’s disease
B. quintana – Trench fever (5 day fever )
Rochalimaea quintana
B.henselae- cat scratch disease
Bacillary angiomatosis
Bacillary peliosis.

19. Epidemic typhus Louse borne typhus /classical typhus /gaol fever
Epidemic during war and famine reported from all part of the world . Common in Russia and Eastern Europe
Typhos = cloud / smoke
Typhus =cloudy state of conciousness
Incubation period days

20. Epidemic typhus Starts with fever and chills
Rash on 4th or 5th day – trunk  limbs(sparing palms and soles ) pt become stuporous and delirious during second week
Case fatality rate 40%  with age
In those who recover from disease ,Rickettsia remain dorment for years in the lymphoid tissue or organs .Reactivation recrudescent typhus
(Brill Zinsser disease )

22. Epidemic typhus Causative agent :R.prowazekii
Named after Von Prowzek died of typhus fever while investigating the disease
Humans are the only natural vertebrate host
Reservoir hosts – squirrels
Vector :Pediculus humanis corporis (body louse )

23. Epidemic typhus
Lice infected by feeding on rickettsiaemic patients , Rickettsiae multiply in the gut appear in the faeces after 3-5 days . Lice defecate while feeding . Infection transmitted when the contaminated louse faeces is rubbed through the minute abrasions caused by scratching . .

24. Epidemic typhus Other modes of transmission
Aerosols and dried faeces through inhalation
Through conjunctiva

25. Endemic typhus Murine or fleaborne typhus
Milder disease than epidemic typhus
Natural infection in rats
R.typhi (R.mooseri)-causative agent
Vector –Xenopsylla cheopis (rat flea)
Rickettsia multiplies in the gut of the flea shed in faeces. Flea is un affected but remain infectious for the rest of life

26. Human infection is a dead end Man to man transmission does not occur .
Mode of transmission
Through the bite of infected fleas .when their saliva /faeces rubbed in
Through aerosols of dried faeces .
Ingestion of food contaminated with rat urine /flea faeces
Human infection is a dead end
Man to man transmission does not occur .

27. NEILL-MOOSER REACTION tunica reaction
Animal inoculation test to differentiate R.typhi and R.prowzekii
Both are closely similar
Blood sample collected from a patient
Inoculated intra peritoneally
Male guinea pigs
Scrotal inflammation
Scrotum becomes enlarged ()
Testes cannot be pushed back into the abdoman because of
inflammatory adhesions between the layers of tunica vaginalis

28. Endemic typhus If test is positivie R.typhi
If test is negative R.prowzekii

29. Tick typhus R.rickettsii  discovered by Ricketts in 1906 .
First insect transmitted bacterial pathogen to be recognised
Causative agent for Rocky mountain spotted fever
Most serious type of spotted fever
Prevalent in north/ south America
Transmitted by ticks  Dermacentor andersoni

30. Rickettsial pox Mildest Rickettsial disease of humans
Self limited , non fatal , vasicular exanthem first observed in New york 1946
Resembles chicken pox
Also called vesicular /varicelliform Ricketsiosis
R. akari-causative agent
Reservoir of infection –domestic mouse
Vector – mite
R. akari has also been isolated from wild rodent in Korea
The disease has also been reported from Eastern Europe and Korea .

31. Scrub typhus Orientia tsutsugamushi – causative agent
Formerly-R.tsutsugamushi
-R.orientalis
Tsutsugam=dangerous
Mushi = insect /mite
It is a place disease
Found only in area with suitable climate plenty of moisture scrub vegetation

32. Scrub typhus Vector –trombiculid mites Leptotrombidium
L. akamushi – Japan
L.deliensis- in India
The mite inhabit sharply demarcated areas in the soil where the micro ecosystem is favourable
. (Mite islands)
Humans are infected while passing through these Mite islands. Bitten by mite larvae (Chiggers)
Chigger – borne typhus

33. Scrub typhus
The mite larvae feed on the serum of warm blooded animals only once during its cycle of development .
Adult mites feed only on plants
Resrviors –rodents and birds
Scrub typhus originally found in scrub jungles sandy beaches, mountains ,deserts & equatorialrain forests.
Zoonotic tetrad
4 factors essential for establishment of disease
Orienta tsutsugamushi
Chiggers
Rats
Transitional forms of vegetation
Incubation period -1-3 weeks

34. Scrub typhus Symptoms : fever , headache , conjunctival congestion
A characteristic eschar over the site of mite bite
Regional lymphadenopathy
Maculo papular rash
Pneumonia
Encephalitis

35. The disease is not a serious problem in civilian practice ,but assumes great importance in military medicine especially during jungle war fare

36. Ehrlichiosis Three types of human infections identified .
Resembling Glandular fever –endemic in japan E.sennetsu
Human monocytic Erlichiosis- E.chaffeenis
Human granulocytic Erlichiosis -E. equi- /E.phagocytophila
E. sennetsu-Erlichiosis resembling –

37. Glandular fever type of Ehrlichiosis
Reported from Japan 1954
E.sennetsu- causative agent
Endemic in Japan lymphoid hyperplasia
Atypical lymphocytosis
No arthropod vector
Ingestion of fish carrying infected flukes –human infection

38. Human monocytic Ehrlichiosis
E.chaffeenis causative agent
Vector amblyoma ticks
Reservoir – deer and rodents
Leucopenia ,thrombocytopenia ,and elevated liver enzymes
Multisystem invovement
Fatality rate high

39. Human granulocytic Ehrlichiosis
E. equi- /E.phagocytophila is the causative agent
Vector –ixodid tick
Reservoir –deer,cattle ,sheep
Leucocytopenia , thrombocytopenia
Examination of blood film by giemsa stain –morula form of Ehrlichia
Treatment : Doxycycline

40. ‘Q’ fever Coxiella burnetti Zoonosis Vector –ixodid ticks
Coxiella abundant in tick faeces , survive in dried faeces for long periods
Shed in the milk of infected animals
Particularly abundant in products of conception contaminate environment at parturition

41. Person to person transmission is rare
‘Q’ fever
Human infection
occupational hazard
Veterinary surgeons
Person handling wool or hides
Meat animal products contaminated with Coxiella burnetti
Drinking infected milk
Routes of entry
Through skin mucosa
Inhalation
Ingestion
Person to person transmission is rare
Ticks are not important in human infection

42. Human disease
Acute systemic infection –interstitial pneumonia
Chronic infection – hepatitis ,meningitis , endocarditis
Spontaneous recovery is usual
Coxiella burnetti is an obligate intracellular pathogen primarily affect monocytes –macrophage cells
Remain dormant after recovery in the tissue of the patient for 2-3 years latent infection

43. In dried faeces or wool it survives for a year
It cannot be destroyed with pasteurisation by the holder method but flash method is effective
Lab 
Culture - yolk sac of chicken embryo cell cultures
Serology – CFT,IFA
Isolation of Coxiella from blood, sputum and other clinical specimens possible. But not recommended due to laboratory infection

44. Treatment : Doxycycline Endocardits : combination therapy
Vaccines
Formalin killed whole cells trichloro acetic acid extracts
live attenuated vaccine
Treatment : Doxycycline
Endocardits : combination therapy
Tetracycline +Co- trimoxazole
Tetracycline+ Rifampicin

45. Trench fever/5 day fever
During the first word war more than million cases occurred among soldiers fighting in the trenches in Europe
Disease not fatal .Slow course and prolonged convalescence  considerable loss of man power
Exclusively a human disease
No animal reservoir
Causative agent B. quintana /Rochalimaea quintana
vector – body louse

46. The lice are unharmed but remain infective through out their life
The faeces of lice become infectious 5-10 days after an infectious meal.
The lice are unharmed but remain infective through out their life
Vertical transmission does not occur in lice
Culture
B. quintana grows on blood agar –this is the only rickettsiae which can grow on artificial media
The disease leads to chronic or latent infection

47. Oroya fever Causative agent: Bartonella. bacilliformis
Outbreak of fever killed thousands of workmen in 1870 when the railway line from Lima to Oroya in PERU was built – oroya fever
Some of the survivers developed nodular ulcerating skin lesions - Verruga peruvana
The common etiology of these two condition established by a Peruvian medical student – Daniel carrion in who injected himself with the infected material obtained from a case of Verruga peruvana developed oroya fever and died –
Carrions diseae

48. Daniel carrion

49. Mortality high in untreated cases
Clinical features
Fever
Progressive anaemia – bacterial invasion of erythrocytes
Mortality high in untreated cases
A late sequele in survivors or in those with asymptomatic infection
B. bacilliformis seen inside in RBC and in skin lesions
Pleomorphic gram negative rods
Motile by a tuft of polar flagella
Culture :semisolid agar with rabbit or human blood

50. Bartonella henselae Causative agent – cat scracth disease
Immunodefifient pts (HIV)-
Bacillary angiomatosis
Bacillary peliosis
Vascular nodules / tumours appear on skin and mucosa
Affect liver and spleen
sis
Lymphnode biopsy- smear – staining
Culture –blood agar – prolonged incubation

51. Weil –Felix reaction Serological diagnosis of Rickettsial disease
Simple ,tube agglutination test –heterophile agglutination test
Weil –Felix 1916
Sharing of an alkali stable carbohydrate antigen by some Rickettsia and by certain proteus (non motile )
Proteus vulgaris OX 19 & OX 2
Proteus mirabilis OX K
Sera of patients mixed with proteus antigen produce agglutination in high titres 1:10001:5000 by the second week declines rapidly during convalescence .
False positves  UTI, Typhoid fever ,liver disease

52. Weil –Felix Reaction Heterophyle Agglutination
OX 19
OX 2
OX K
Epidemic typhus
+++ + -
Endemic typhus
Tick born spotted fever ++
Scrub typhus

53. Weil –Felix reaction is not done for the diagnosis of Q fever which is caused by Coxiella burnetti