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Typhus
Typhus is caused by Rickettsia bacteria, which are intracellular parasites carried by arthropod hosts like lice and ticks. There are several types of typhus including epidemic typhus spread by human lice and Rocky Mountain spotted fever spread by ticks. Symptoms can range from mild to severe fever, headache, rash and organ damage. Diagnosis involves identifying the bacteria through PCR testing, antibody levels or tissue staining. Treatment is with doxycycline or chloramphenicol antibiotics.
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Typhus
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- 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 • Widespread vasculitisand endothelial proliferation affect organs • Thrombotic occlusion gangrene
- 4. • Travellers/ inhabitantsof 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 • Brill Zinnser Disease • Rash: truncal, then peripheral
- 8. Rocky Mountain Spotted Fever • R. rickettsii • Tick- borne • Rash begins as macules on hands/feet Spreading, becoming petechial or hemorrhagic
- 9. Tick Typhus • R. conorri • 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 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
- 16. 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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