Typhus

Typhus is a group of infectious diseases that includes endemic typhus, epidemic typhus, and scrub typhus. Endemic typhus is caused by Rickettsia typhi, which is transmitted via rat and cat fleas. Epidemic typhus is caused by R. prowazekii, which is transmitted by the body louse. Scrub typhus is caused by Orientia tsutsugamushi, which is transmitted by chiggers (mites) from rodents. All three types of typhus manifest with flu-like symptoms and a maculopapular or petechial rash that spreads from the trunk to the extremities. Symptoms in epidemic typhus are often more severe and can include neurological symptoms (e.g., seizures). Clinical features of scrub typhus also include an eschar at the site of mite attachment and lymphadenopathy. Relative bradycardia despite fever may also be seen in scrub typhus. Diagnostics for all three types include serology and positive Weil-Felix reaction, and treatment of all three types includes doxycycline or chloramphenicol.

• Definition: an exanthematous typhus fever caused by Rickettsia typhi
• Epidemiology: occurs worldwide, mainly in warm coastal regions, southern US
• Pathogen: Rickettsia typhi
• Transmission: : via vector (rat and cat fleas)
• Clinical features
  • Incubation period: 8–16 days
  • Fever, severe headache, malaise
  • Maculopapular or petechial rash erupts on the trunk; and spreads to the extremities (palms and soles are spared).
  • No eschar (scab at site of flea bite)
  • Relative bradycardia ^[1]
• Diagnostics
  • Indirect immunofluorescence (four-fold rise in antibodies)
  • Positive Weil-Felix reaction: a diagnostic test for rickettsial infections, whereby suspensions of proteus antigens (OX 19, OX 2, or OX K) are mixed with a patient's serum ^[2]
    • Agglutination occurs in the serum of patients infected with Rickettsia.
    • No longer recommended in routine practice due to low sensitivity and specificity
    • Still valuable test in resource-limited areas where indirect immunofluorescence is not available
• Treatment: doxycycline OR chloramphenicol

The rash of Typhus starts on the Trunk.

• Definition: an exanthematous typhus fever caused by Rickettsia prowazekii
• Pathogen: Rickettsia prowazekii
• Transmission: via vector
  • Feces of infected body louse
  • The louse is transmitted by direct contact
• Epidemiology
  • Extremely rare in the US
  • Occurs mainly in central and eastern Africa, central and South America, and Asia ^[3]
• Clinical features
  • Abrupt onset of fever, severe headache, malaise, myalgia, abdominal pain, nausea, cough
  • After 4–5 days: maculopapular or petechial rash that spreads from the trunk to the extremities
  • Possibly neurological symptoms: e.g., confusion, coma, seizures
  • Brill-Zinsser disease: exacerbated recurrence many years after the primary episode
• Diagnostics
  • Serology
  • Positive Weil-Felix reaction
• Treatment: doxycycline OR chloramphenicol

The rash of Typhus starts on the Trunk.

• Definition: an exanthematous typhus fever caused by Orientia tsutsugamushi.
• Epidemiology: occurs mainly in central, eastern, and southeast Asia, as well as northern Australia and South Pacific
• Pathogen: Orientia tsutsugamushi
• Transmission: via vector Trombicula mites larvae (chiggers) from rodents
• Clinical features
  • Incubation period: 7–10 days
  • Fever, severe headache, myalgias, arthralgia, cough
  • Maculopapular rash
  • Eschar at site of mite attachment
  • Lymphadenopathy
  • Relative bradycardia despite fever
• Diagnostics
  • Serology (four-fold rise in antibodies)
  • Positive Weil-Felix reaction
• Treatment: doxycycline OR chloramphenicol