2. Group of bacteria that are fastidious, obligate
intracellular pathogens
They are pleomorphic & coccobacillary
The organisms will not show up on Gram
stain, but can be seen when either Gimenez or
Giemsa stains are used
3.
4. Spotted Fever Group
Typhus Group
Transitional group
The Others
The outer membrane protein A (ompA) gene
is present in spotted fever but not typhus
group organisms
5.
6.
7.
8. Rickettsia are usually introduced into human
skin by the bite of an insect (flea or louse) or
an arachnid (tick or mite)
These arthropods serve as both host and
vector to the rickettsia and reside on the
reservoir animals (dogs, mice, rats, and flying
squirrels)
9. Two of the rickettsial diseases are unique in
that humans may acquire them by direct
inhalation
Q fever (Coxiella burnetii)
Epidemic typhus (Rickettsia prowazekii)
12. very similar for all infections regardless of
species
Vasculitis caused by the invasion and
multiplication of the organism in the
endothelial and smooth muscle cells of the
blood vessels
13.
14. Thrombosis, occlusion, and necrosis of blood
vessel walls
Thrombocytopenia with hemorrhage
Massive capillary leakage into the interstitial
spaces results in edema, hypovolemia,
hypotension, and adult respiratory distress
syndrome (ARDS)
Encephalitis, myocarditis, & nephritis are the
common clinical consequences
Hyponatremia is due to ADH response
16. IP: 2 to 14 days
H/o exposure to tick/ close contact with pets/
Endemic area/ similar illness in family
17. Initial Non-specific symptoms – Calf muscle
pain and tenderness are more common in
children.
Gastro-intestinal symptoms are more
commonly associated
Skin rash: 2-4 days after onset of illness.
22. Rocky Mountain spotted Fever:
-Rash typically appears on 4th day as
blanching maculopapular lesions on the
extremities
Louse borne or Epidemic typhus:
-Rash first appears in axillary folds then
involving the trunk and extremities.
- Brill-Zinsser disease
23. Murine (fleaborne or endemic) typhus:
- Relatively mild illness with less
complications
-Rash is non-purpuric,non-confluent,less
extensive
-History of a flea bite and the presence of
rats in the house support the diagnosis but
this is only reported 30% of the time.
24. Scrub typhus:
-Occurs mostly in Asian countries
-characterised by painless eschar and
“satellite lymphadenopathy”
Rickettsial pox:
-best known because of its association with a
varicelliform rash.
25. Usually does not affect children
No vector is involved
Presents as both acute or chronic forms
Endocarditis in chronic variety
Bioterrorist threat?
26. Low or normal WBC count; in the late stages
there is leucocytosis
Anemia, thrombocytopenia and elevated
serum transaminases
Hyponatremia
CSF analysis is usually normal; rarely
mononuclear plecytosis (<300 cells/micro L)
27. Serological evidence of infection usually not
occur earlier than second week of illness.
28. Gold standard test
IgM titre >1:64
IgG titres >1:64 but <1:125 suggests
previous infection
A single titer is neither sensitive (patients can
die before seroconversion) nor specific (an
elevated titer can represent prior infection)
ELISA – available in India and is the preferred
diagnosis at present
29. Slide agglutination test
Tests the presence of antigenic cross-
reactivity between Rickettsia spp. and certain
serotypes of non-motile Proteus spp.,
suffers from poor sensitivity and specificity,
with a recent study showing an overall
sensitivity as low as 33% and specificity of
46%.
33. Drug of choice for all ages –
Doxycycline(4 mg/kg/day divided every 12 hr
PO or IV, maximum 200 mg/day)
Chloramphenicol – Allergy to Doxycycline,
Pregnant women (50-100 mg/kg/day divided
6th hourly, max 3 g/day)
Continued for minimum of 5-7 days and for
atleast 3 days until patient is afebrile.
34. Azithromycin, Clarithromycin
Fluoroquinolones
Rifampicin
-Found to be more effective in typhus groups.
35. Patient coming from endemic area.
H/O contact-pets/ h/o tick bite.
Classical triad
Rash without coryza.
hepatosplenomegaly,edema,gangrene,anemia,thrombocyto
penia
Fever,rash,altered sensorium, convulsions
PUO and not responding to routine antibiotics
36.
37.
38. When applied to the patients presenting with
fever of unknown source, a clinical score of
14 or more on the proposed scoring system
has very high sensitivity and specificity for
the diagnosis of spotted fever group of
rickettsial diseases.