The chance of a head lice infestation goes up in schools where lockers and coat hooks are shared, not assigned. Head lice are spread by person to person contact and sharing of personal items like combs, hairbrushes, and head ware. Unlike the head louse, body lice spend much of their time on clothing, usually in areas where the cloth is in contact with the body. Eggs are laid on clothing as well. They generally occur in crowded, unsanitary conditions.
Body lice are uncommon in most of the U.S. population.
As the name suggests crab lice look superficially like tiny crabs with their enlarged second and third pairs of legs. As with other lice, person to person contact is the most common means of transmission. Lice cannot survive off their human host for long. Therefore there is little benefit from treating the whole house with insecticide. Rather, you must concentrate your efforts on where lice live.