A comprehensive description about various rickettsial infections encountered in Pediatrics

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

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

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)

10. Disease Rickettsial Agent Insect Vector Mammalian
Reservoir
Indian tick typhus R.conorii Tick Dog/Rodents
RMSF R.rickettsi Tick Dog/Rodents
Rickettsial pox R.akari Mite Mice

11. Disease Rickettsial Agent Vector Mammalian
Reservoir
Epidemic typhus R.prowazeki Louse Humans
Murine typhus R.typhi Flea Rodent
Scrub typhus R.tsusugamushi Mite Rodent

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

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

15.  Rocky Mountain spotted fever
 Murine (Endemic) typhus
 Epidemic typhus
 Q fever

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.

18. Fever
Headache
Rash

19. Necrotic
petechiae
Maculopapular

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%.

30. Rickettsia Agent Antigen
Spotted Fever Group
OX 2 (Pr.vulgaris)
Typhus Group, RMSF OX 19 (Pr.vulgaris)
Scrub typhus OX K (Pr.mirabilis)

31.  Complement fixation
 Latex agglutination
 Microagglutination
 Immunoperoxidase assay

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

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.