The parasite infests the armpits, beard, eyebrows, eyelashes, and
particularly the pubic region, where it takes blood meals; females attach eggs to hairs.
The incubation period requires from 7 to 10 days. Nymphs reach the
adult stage in about 15 days.
5-49. EPIDEMIC TYPHUS AND RELAPSING FEVER
a. Epidemic Typhus
(1) First week. While the onset of this louse-borne disease is variable,
typically the 6- to 15-day incubation period is followed by sudden onset of chills,
headache, general pains, and malaise. Fever, which is low during the early part of the
first week, rises steadily and rapidly and is accompanied by excruciating headaches. A
rash occurs on about the fifth or sixth day.
(2) Second week. During the second week, fever remains elevated and the
patient becomes desperately ill.
(3) Third week. Recovery may occur in the third week, otherwise death from
urea in the blood, pneumonia, circulatory collapse, or some other immediate cause may
occur. In epidemics, from 10 percent to 40 percent of the cases terminate fatally in the
absence of specific therapy.
(4) Transmission. Transmission of the etiologic agent, Rickettsia prowazekii,
seldom occurs through the actual bite of the louse. Instead, scratching of the itching
louse bites has the effect of rubbing rickettsiae-laden louse feces or juices from crushed
lice into the bite wounds or other skin abrasions.
(5) Immunity/recurrence. One attack usually confers lasting immunity to
reinfection; however, a recurrence (Brill's disease) may occur several years after the
primary attack and in the absence of lousiness. The recurrence is not so severe as the
primary attack, but the patients are infective to lice and may serve as the foci of new
outbreaks of epidemic typhus in susceptible, louse-infected populations. Tetracycline
antibiotics or chloramphenicol usually renders the patient afebrile.
b. Epidemic Relapsing Fever. This disease occurs in limited localities in Asia,
Eastern Africa, North and Central Africa, and South America. Epidemics are common in
wars, during famines, or wherever malnourished, overcrowded populations with poor
personal hygiene and the body louse coincide. Causative agent of the disease is the
spirochete, Borellia recurrentis.