Harry Williams, Professor, ancl Jaimes Yanes, Jr., former Assistant Professor Entomology and Plant Pathology

Common Name		Scientific Name
Body Louse		Pediculus humanus humanus L.
Head Louse		Pediculus humanus capitis DeG.
Crab or Pubic Louse		Phthirus pubis (L.)

Human lice infestations can be detected by the feel of something crawling over the skin or by using a hand lens or reading glass to see the minute grayish louse. Infestations can cause intense itching and scratching and, in severe situations, result in scarred, hardened, pigmented skin known as "hobos disease." Inspection of the hair may reveal louse eggs (nits). Outbreaks seem to be associated with crowded conditions with limited facilities for bathing and laundering.

Identification

Human lice are small, wingless insects with sucking mouthparts, head narrower than the thorax and legs designed for grasping hairs or fibers. The body louse (about 1/8 inch long) is similar to the head louse (about 1/6 inch long). Both have grayish-white bodies; the head louse has dark areas along the abdominal side. The crab louse is broadly oval, somewhat crab-shaped with large claws on the middle and hind legs, about 1/16 inch long and dirty white to pink. Lice eggs are 1/16 inch long.

Life Cycle and Habits

The three species of lice are similar in development. Egg are cemeted to hairs, by the head or crab louse, and to clothing fibers and seams by the body louse. Eggs hatch in eight to 10 days at 80 F to 85 F. Eggs do not hatch when temperatures are below 70 F for seven to nine days. The louse nymphs (immatures) feed on blood meals and molt three times before becoming sexually mature adults. Mated females deposit eggs daily over a 20- to 30-day period. Body lice deposit 275 to 300 eggs, head lice 50 to 100 eggs and crab lice about 30 eggs per female. The entire life cycle requires 18 to 27 days, with the adults living up to 35 to 40 days.

The body louse lives on clothing in close contact with the skin. This louse is most common in overcrowded, unsanitary conditions often when clothing is not changed regularly. People sleeping or huddled together in their clothing aid the spread of lice. Lice infested clothing in lockers, closets or bedding are sources of infestation. This louse is a vector of several diseases, such as epidemic typhus and relapsing fever. The adult body louse can survive no longer than 10 days off its host. All stage, including eggs, die within 30 days away from the host.

The head louse commonly infests school children, in addition to adults. Eggs are firmly attached to the base of hairs, usually behind the ears and on the back of the neck. These lice are spread by direct contact with infested persons, or by using infested articles, such as hats, wigs, hairbrushes, combs, towels, scarves and hair rollers. Lice may also be spread among the population by using the bed or other furniture of an infested person. Head lice are usually not found below the neck of an individual, but were recorded in armpits and even the chest.

Crab lice are found primarily in the pubic region, but may occur in the armpits, beards and eyebrows. These lice may be spread during sexual intercourse and only rarely are spread by loose hairs left on bedding and toilets by infested persons. Crab lice die after 24 hours if not attached to a human.

Control Measures

Control of human lice is a medical problem that must be left to a physician, pharmacist or health department personnel. Chemical treatment of these premises is seldom necessary because lice cannot live off the host for indefinite periods of tune. Schools, jails, hospitals, boarding houses and other crowded living quarters need a public educational program for effective lice control.

Prevention: Proper sanitation is critical in lice control. Hair should be washed frequently, bedding and undergarments laundered, clean clothing worn and premises thoroughly cleaned with hot water and a strong cleaning agent, such as disinfectant. Laundering or dry cleaning infested bedding and garments will kill body lice. Adult lice are killed within five minutes and the eggs within 10 minutes in 125 F water. Regular changes to properly laundered clothing will soon eliminate body lice. Long hair tightly braided and thoroughly combed each day ean minimize head lice problems. Special combs with teeth set close together are used to remove nits and adult head and crab lice. These combs, available at pharmacies and pet shops, can also be ordered from Cereal Soaps, Division Johanson Manufacturing Corp., Box 329 Boonton, NJ 07005.

Insecticides: When a premise treatment is required, a formulation of pyrethrum plus lindane can be applied in louse-infested clothing lockers, but the value is questionable as lice do not live off the body for indefinite periods of time. Lice can be killed with old-fashioned green soap (coconut oil base) or shampoo. Most chemicals for lice control are sold on a prescription basis through a physician. Lindan (Kwell) 1 percent shampoo, lotion or cream, and DDT (Toppocide) 1 percent lotion obtained by prescription will kill nits, nymphs and adult lice. Nonprescription insecticides for human louse control include pyrethrins (A-200 Pyrinate), Cuprex and Bornate. These do not always kill the eggs, making repeat applications necessary. More recently, lotions of 0.5 percent malathion and carbaryl are readily available and effective. Tests also indicate that for head or crab louse control, dusts of 1 percent malathion or 5 percent carbaryl (Sevin) give control after a second treatment in 10 days. Before using insecticides, read the label and follow directions.