a. Life Cycle. All lice have three stages of development during their life cycle.
These are the egg, the nymph, and the adult. In the nymph stage, the louse looks like a
b. Species of Military Importance. Three species of lice that are of importance
are the body louse, the head louse, and the crab louse (figure 5-6). They live on human
blood. If they are unable to feed, they will die in a relatively short time. Lice are spread
by contact with infested persons or contact with things onto which adult lice or eggs
have dropped such as straw, debris, blankets, clothing, or latrine seats.
Figure 5-6. Adult lice. A Body louse. B Head louse. C Crab louse.
5-11. LOUSE-BORNE DISEASES
The louse-borne diseases are typhus fever (epidemic), relapsing fever, and
trench fever. Of these, epidemic typhus is the most important. Trench fever was very
common among European armies during World War I, but has greatly declined in
incidence since then. Relapsing fever is usually present wherever epidemic typhus
occurs. These diseases are spread from man-to-man by lice and occur in epidemics.
They are serious infections and are a special threat to armies. A good vaccine against
typhus fever is available, but as yet none is available for relapsing fever or trench fever.
a. Disease Transmission. Disease is seldom transmitted by the actual bite of
the louse. The disease organisms contained in the gut of the louse are excreted with
the droppings of the louse when it feeds. Louse bites itch. When the person scratches,
the feces containing the disease organisms are rubbed into the tiny skin abrasions.
Scratching also may crush the louse and rub the disease organisms contained in its
intestines into the wound. This is especially true in the case of relapsing fever.
b. Body Lice. Body lice are the vectors of epidemic typhus. They remain in the
clothing except when feeding on a person's body. They attach their eggs to the fibers of
clothing, especially along the seams, and occasionally to body hair.