Rickettsia typhi

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Rickettsia typhi /
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  • Causes murine typhus or flea-borne typhus

Microbiology

  • Flea-borne Gram-negative intracellular bacterium Rickettsia typhi

Life Cycle

  • Flea bites, flea poops, feces get rubbed into the bite wound
  • Flea acquires infection from feeding on a rickettsemic host

Epidemiology

  • Flea vector (Xenopsylla cheopis) with a rat reservoirs (Rattus spp.)
    • Also, cat flea vector (Ctenocephalides felis) in sourthern US
    • Possibly opossums as reservoirs
  • Worldwide distribution
  • In the US, most cases are in southern Texas and California

Clinical Presentation

  • Incubation period of 1 to 2 weeks, but rarely remember flea exposure
  • Fever, headache, nausea and vomiting are common, as well as myalgias
  • Rash develops over the course
    • Usually described as maculopapular, sometimes with petechiae
    • On trunk, but can involve extremities
    • Rarely on palms and soles
  • May have leukopenia and thrombocytopenia early in the course
  • Elevated AST is common, as well as other liver enzymes
  • Further nausea/vomiting and anorexia, cough, and hepatosplenomegaly may all develop
  • Neurologic complications include confusion, seizures, and ataxia
  • They often develop hypoalbuminemia and electrolyte abnormalities such as hyponatremia and hypocalcemia
  • CSF shows aseptic meningitis
  • 1 to 4% mortality
  • Sort of like a milder version of R. prowazekii