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Epidemic Typhus Fever

Epidemic typhus fever, as the name implies, has the potential to cause serious disease in large numbers of people under certain conditions that contribute to heavy infestations of body lice. Indeed, historical accounts such as Rats, Lice, and History (see references below) have chronicled the impact of epidemic typhus fever, especially in association with war and natural disasters when outbreaks of body lice occur among people in refugee camps. Today, outbreaks of epidemic typhus are limited, but the disease has the potential to re-emerge. Examples include in Burundi (Africa) refugee camps in 1997-1998, when about half a million people were afflicted, and in China in 1999, when more than 5,600 people were afflicted following an earthquake.

Rickettsia prowazeckii and flying squirrels

Rickettsia prowazeckii has been isolated from southern flying squirrels, Glaucomys volans, an apparent reservoir host. The flying squirrels were removed from attics of houses in which human cases of epidemic typhus fever occurred. Very few cases have been reported, however, all from the eastern and southeastern U.S. Details of transmission are not fully known, but available evidence suggests that human infections resulted from inhaling infected feces of a louse that is a host-specific parasite of the southern flying squirrel. This louse and the human body lice were not involved in transmission to humans.

Causative agent

  • A bacterium, specifically a rickettsia with the scientific name Rickettsia prowazekii.
  • It is an intracellular parasite that invade cells lining the walls of small blood vessels.

Geographical distribution of cases

  • Formerly in temperate regions, but now limited primarily to high elevations in the subtropics and tropics.
  • NOTE: Potential exists for transmission in the U.S. among homeless infested with body lice.

Symptoms of infection

  • Fever, malaise, head and muscle ache, cough, and general weakness.
  • Blotchy rash that spreads from the abdomen to chest to rest of body, but rarely to hands and feet.
  • Severe disease includes prostration, delirium, very low blood pressure, and coma.
  • NOTE: The death rate can be very high during epidemics.

Reservoir of Rickettsia prowazekii

  • Humans who survive infection and harbor rickettsiae in their lymph nodes for months to many years.
  • NOTE: A re-occurring human infection, Brill-Zinsser disease, is the source of rickettsiae to body lice.

Vectors of Rickettsia prowazekii

  • The human body louse Pediculus humanus.

Mode of transmission

  • Via feces of infected body lice being scratched into the skin by an infested human.

Diagnosis of infection

  • Symptoms together with an infestation of body lice.
  • Laboratory tests that detect antibodies to Rickettsia rickettsii in a patient's blood.

Treatment of infection

  • An antibiotic prescribed by a physician.

Prevention of infection

  • There is no vaccine available in the U.S.
  • NOTE: A vaccine used in Africa is ineffective and has caused adverse side effects in some people.
  • Avoid human body louse infestations.
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