Typhus is caused by Rickettsia bacteria, which are intracellular parasites transmitted through arthropod bites like lice and ticks. Rickettsia infect endothelial cells and cause vasculitis. Symptoms include fever, headache, rash and can lead to organ damage. Diagnosis involves identifying the bacteria through PCR on skin biopsies or blood or detecting antibodies. Treatment is with doxycycline or chloramphenicol antibiotics. Prevention involves vector control and vaccines, though available vaccines are not very effective.

1. Typhus
The Rickettsial Disease

2. Rickettsiae:
• parasitic bacteria
• Obligate intracellular parasite
• Bigger than virus
• Smaller than bacteria
• Carried by host arthropods
• Invade human mononuclear cells, neutrophils, bld
vessel endotheliums

3. Pathology
• Rickettsia are transmitted to humans by the bite of
infected arthropod vector
• Multiply at the site of entry and enter the blood
stream
• Widespread vasculitis and endothelial
proliferation affect organs
• Thrombotic occlusion  gangrene

4. • Travellers/ inhabitants of endemic areas likely have
septicemia but (-)cultures ?Typhus
• Incubation period: 2 -23 days

5. Signs
 Mild/ asymptomatic
 Severe/ systemic: sudden fever, frontal
headache, confusion & jaundice
 Eschar: dark crusty ulcer at the site of a bite
 Rickettsial rash: macular, papular, petechial or
hemorrhagic

6. Laboratory
• Hemolysis
• Neutrophilia
• Thrombocytopenia
• Dec clotting
• Hepatitis
• Renal impairment

7. Epidemic typhus
• R. prowazeki
• Spread: human lice Pediculus humanus corporis
• Brill Zinnser Disease
• Rash: truncal, then peripheral
• Incubation period: 5 – 21 days

8. Rocky Mountain Spotted
Fever
• R. rickettsii
• Tick- borne
• Most serious form
• Incubation period – 1 week
• Rash begins as macules on hands/feet
Spreading, becoming petechial or hemorrhagic
• More similar to typhus fever but the rash appears
earlier and is more prominent.

9. Tick Typhus
• R. conorri
• Boutonneuse fever
• Rash starts in axilla
• Becoming purpuric as it spreads
• Conjunctival suffusion
• Jaundice, deranged
clotting, meningoencephalitis, renal
failure, cerebritis

10. Scrub typhus
• Oriental tsutsugamushi
• Most common in SE Asia
• Signs:
• Eschar from chigger bite
• Hepatomegaly, cough, lymphadenopathy, tachyp
nea, abdominal
pain, constipation, edema, splenomegaly, vomiting
, rash, petechiae, sudden deafness,

11. Scrub typhus
• CXR: bilateral infiltration
• Blood: LFT
inc, thrombocytopenia, neutrophilia, lymphocytosis,
+/- atypical lymphocytosis
• Complications: pneumonia, pulmonary
edema, meningitis, shock

12. Murine Endemic Typhus
• R. typhi
• Spread: fleas from rats (Xenopsylla cheopis)
• Reservoir: Rat
• to humans
• Prevalent in warm coastal ports

13. Diagnosis
• clinical history
• physical exam
• tests based on identification of the bacterial genus
and species by PCR testing of skin biopsy of skin
rash, skin lesions/blood samples
• immunohistological staining that identifies the
bacteria within infected tissue (skin tissue, usually)
• Dx late or after the disease has been treated with
antibiotics, when significant titers of antirickettsial
antibodies are detected by immunological
techniques.

14. Diagnosis
• CBC: show anemia and low platelets
• High level of typhus antibodies
• Low level of albumin
• Low sodium level
• Mild kidney failure
• Mildly high liver enzymes

15. ISOLATION
• Blood is inoculated in guinea pigs/mice.
• Observed on 3rd – 4th week.
• Animal responds to different rickettsial species can
vary
• Symptoms:
• Rise in temperature – all species.
• Scrotal inflammation,swelling,necrosis –
R.typhi, R.conori, R.akari ( except R.prowazekii)

16. Serology
• Reliable test to confirm rickettsial diseases
• Antibody detection by Weil-felix test
• Antigen detection by IFA

17. WEIL-FELIX TEST
• Heterophile agglutination test using
• non motile proteus strains (OX 19, OX 2, OX K)
• to find rickettsial antibodies in patient’s serum.
• Procedure:
• Serum is diluted in three separate series of tubes
followed by the addition of equal amount of
OX19,OX2,OXK in 3 separate series of tubes.
• Incubation at 370C for overnight.
• Observe for agglutination

18. WEIL-FELIX TEST
• Strong Agglutination with OX 19 – means epidemic
& endemic typhus.
• Strong agglutination with OX 19 & OX 2 –
• means Spotted fever
• Strong agglutination with OX K – Scrub typhus
• (Scrub typhus by Orientia tsutsugamushi
• (one of the rickettsial disease)

19. PROPHYLAXIS
• Vector control
• Live vaccine & killed vaccine are available but not
much effective

22. Treatment
• Doxycycline 100mg/ 12hrs PO/IV for 7 days or
48 hours after temp is normal
• Chloramphenicol 500mg/ 6 hours PO for 10-14 days
• Azithromycin 500 mg 1 dose for tick & Scrub typhus

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