DISEASES TRANSMITTED BY LICE
a. General. Typhus fever (epidemic) is rickettsial disease which may survive in
lymphoid tissues for many years; recurrence is possible (Brill's disease). Epidemic
louse-borne typhus is caused by an infection with Rickettsia prowazekii, which is a
parasite of the body louse. Ultimately, the parasite kills the louse. Transmission of this
disease is prevalent in crowded living conditions, war, famine, or any kind of situation
that predisposes heavy infestation of lice. If the louse sucks the blood of a victim
infected, the organism starts growing in the gut of the louse and stays there. When the
louse then has a blood meal off another victim, the louse defecates simultaneously, and
the infected feces are rubbed into the bite wound when it itches. It is also possible for
dry, infectious louse feces to enter the respiratory tract mucous membranes, causing
human infection. Once the typhus patient has been bathed and deloused, he is no
longer infectious for other humans.
b. Signs and Symptoms. Following an incubation period of 10-14 days, the
patient begins to have chest pains, coughing, headache, and prodromal malaise. After
this comes "influenzal symptoms" that progress to stupor and delirium. Other
symptoms are flushed face, conjunctivitis, and rales at the lung bases. Following this is
a macular rash (soon it is papular) appearing in the axillas, then the trunk and onto the
extremities. The rash seldom goes to the face, palms, or soles. In nonepidemic
conditions, the prodromal symptoms and the beginning febrile stage are not specific
enough for diagnosis of typhus--sometimes even the rash is missing or difficult to see in
c. Treatment. Tetracycline, parenteral fluids, and oxygen may be administered.
A vaccine is available that gives good protection against severe disease; however, it
does not prevent infection or mild disease. The best prevention of the disease is louse
control with insecticides and frequent bathing.
Another louse-borne disease is relapsing fever which was previously
described under tick-borne diseases.
Section IV. FLEA-BORNE DISEASES
Fleas which attack humans live primarily on cats, dogs, and rodents. Rodent
fleas are the vectors for the transmission of plaque and typhus fever (murine). When
the normal rodent hosts are unavailable, rodent fleas will readily attack man. Plaque is
transmitted through the bite of the infected flea. Typhus fever (murine) is transmitted
when flea feces or crushed fleas are scratched into the skin.