Infection: Lice Infestation

Definition
Description
Demographics
Causes and Symptoms
Diagnosis
Treatment
Prognosis
Prevention
The Future
For more information

Definition

A lice infestation is a condition in which lice are present on a person's scalp, body (or clothes), or pubic area. It is called an infestation rather than an infection because the parasites live on or near the skin and outside of the body rather than in the internal organs. Lice are tiny insects that can spread from one person to another through close contact;

through sharing such personal items as clothing, hats, combs, or hair-brushes; or through lying on a bed, pillow, or carpet that has been in contact with someone with lice.

Description

The three types of lice that infest humans are somewhat different in size and outward appearance. Head lice are 1–2 millimeters long, white or gray in color, and have flattened abdomens. The female louse lays her nits (eggs) close to the base of a hair shaft and attaches them to it with a sticky, glue-like substance. The glue is what makes it so difficult to remove the nits from the hair shaft.

Body or clothing lice are generally larger than head lice, between 2 and 4 millimeters long. The body louse lives in the seams of clothing, emerging at night to feed on the person's body. Pubic lice are smaller and broader, about 1.2 millimeters long. They have larger front claws, which is why pubic lice are sometimes called “crabs.” The claws enable pubic lice to cling to the coarse hairs in the human groin and armpit areas.

Demographics

The demographics of lice infestation vary depending of the type of lice involved. On the whole, lice infestations are common in the general population. There are at least 12 million cases in the United States each year, although this figure is only an estimate. Head lice infestations are often not reported because people find them socially embarrassing—even though the Centers for Disease Control and Prevention (CDC) states that: “Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice.” The number of all three types of lice infestations in North America has increased in recent years.

Head lice are most common in schoolchildren between the ages of three and eleven, and their families. Girls are more likely to be infested than boys because they are more likely to share clothing and other personal items with friends. It can be difficult to prevent a child from picking up head lice at school because of the amount of close contact among children and their belongings.

Body lice infest both children and adults. There is no difference in frequency between men and women. Homeless people and others who live in crowded conditions without opportunities to bathe or shower regularly are at greatest risk of getting body lice. Because the body louse lives in clothing, infestations occur in colder climates. Pubic lice are most

common in people between the ages of fourteen and forty who are sexually active.

There is some seasonal difference in lice infestations in temperate climates. Head lice infestations are more common during the warmer months while body and pubic lice infestations are more common in the fall and winter.

Causes and Symptoms

The cause of lice infestations is the presence of head, body, or pubic lice on a person's body or in his or her clothing. The life cycle of lice helps to explain some of the symptoms of an infestation. When the nit or egg hatches, about eight or ten days after being laid, it produces an immature louse called a nymph. The nymph needs blood to survive. It has sucking mouth parts on its head that can pierce the skin and draw blood to feed on. Human lice must feed about five times a day to survive, otherwise they become dehydrated and die. The nymph becomes a mature adult about ten days after hatching. Its complete life cycle is between thirty and thirty-five days in length.

The symptoms of a lice infestation depend on the area of the body that is affected:

• Head lice: itchy scalp due to an allergic reaction to the bites of the lice; small red bumps on the head or neck; sensation of something moving over the scalp; an irritated rash caused by scratching the itchy parts of the scalp.
• Body lice: itching and a rash caused by an allergic reaction to the bites of the lice. A long-term infestation may cause discoloration of the skin of the waist area and upper thighs. There may also be open sores caused by scratching the itching areas; these raw areas can become infected by other disease organisms.
• Pubic lice: itching in the genital area or other body areas with coarse hair (armpits, mustache area, eyebrows, eyelashes), and visible nits or lice crawling in the affected area.

Diagnosis

The diagnosis of lice infestation is usually made by examining the skin, hair, pubic area, or clothing of the affected person. The doctor can collect nits from the hair by using a fine-toothed comb or remove lice from the body with a piece of cellulose tape. The organisms can then be studied under the microscope to determine the type of lice involved.

Another test that can be performed involves the use of a Wood's lamp, which is a device that uses ultraviolet light to detect lice, fungal infections, and a few other types of skin infections. The patient is taken into a dark room while the doctor shines the lamp on the area that may be infested. If lice or nits are present, they will glow greenish-yellow.

Treatment

Treatment of head lice requires washing the infested person's clothing and bedding in hot water at 130°F (54.5°C) two days prior to treatment. Clothing that is not washable should be dry-cleaned. Combs and brushes should be soaked in rubbing alcohol for an hour or washed in soap and hot water. These steps are necessary to lower the risk of reinfestation. Toys or other personal items can also be cleared of lice by sealing them inside a plastic bag for at least two weeks; the lice will die from lack of air and food.

The treatment itself consists of applying an over-the-counter or prescription shampoo to the scalp that contains a drug that kills lice. The product directions should be followed exactly regarding how long the product should be left on the hair and whether it should be rinsed out afterward. Following the application, a fine-toothed or special nit comb should be used to comb nits out of the hair. This combing should be repeated every two to three days for three weeks to make sure all the lice and nits are gone. Retreatment with the medicated shampoo may be necessary.

A Poem to a Louse

Most people would not think of a head louse as a pleasant topic for a poem. But one of the best-known poems by Robert Burns (1759– 1796), Scotland's national poet, is about seeing a louse crawling up and down a lady's bonnet during a church service. The poem, written in 1786, is a commentary on class snobbery.

In the poem, Burns appears to criticize the louse for its “impudence” in choosing “sae fine a lady” for its host. He tells the creature to “gae somewhere else and seek your dinner/On some poor body.” But it is obvious by the end of the poem that he is poking some fun at the well-dressed lady, proud of her expensive bonnet, who is totally unaware that a parasite she would associate with poor people has attached itself to her own head. Burns wrote in Scots dialect rather than standard modern English.

Another treatment that has been found effective in treating head lice is a drug called Mectizan (ivermectin), which was originally

developed to treat intestinal parasites. The person needs to take only one dose of the drug.

Body lice are treated by removing all the infested person's clothing and either destroying or washing them in hot water followed by at least twenty minutes in a dryer on the hot setting. The person must take a shower and change into clean clothing. A lice-killing shampoo may be applied to the hairy parts of the person's body.

Pubic lice are treated by applying a shampoo, mousse, or lotion containing a drug called pyrethrin. These products can be purchased over the counter at a pharmacy and should be used exactly as directed on the container. There is also a drug called Ovide that requires a doctor's prescription that can also be used to treat pubic lice. Pubic lice in the eyebrows must be treated by applying a prescription ointment, as Ovide and the over-the-counter products should not be used close to the eyes.

Prognosis

The prognosis for treatment of lice is extremely good provided care is taken afterward to prevent reinfestation. Head lice and pubic lice are not known to spread other diseases. Body lice, however, are dangerous because they can transmit three potentially fatal illnesses: typhus, relapsing fever, and trench fever.

WORDS TO KNOW

Crabs: A slang term for pubic lice.

Host: An organism that is infected by a virus, bacterium, or parasite.

Infestation: A condition in which a parasite develops and multiplies on the body of its host rather than inside the body.

Nits: The eggs of lice.

Wood's lamp: A special lamp that uses ultraviolet light to detect certain types of skin infections and infestations. It was invented in 1903 by physicist Robert Wood.

Prevention

Practicing good personal hygiene, avoiding sharing personal items with others, and prompt treatment of lice infestations are the best ways of preventing the spread of lice.

The Future

Lice are not likely to disappear from the human scene any time soon. Scientists estimate that lice have been infesting humans for at least 3 million years. It is possible that researchers will discover more effective shampoos or soaps to get rid of lice, but for the time being, the best medicine is prevention.

For more information

BOOKS

Hirschmann, Kris. Lice. Farmington Hills, MI: Kidhaven Press, 2004. Somervill, Barbara A. Lice: Head Hunters. New York: PowerKids Press, 2008.

PERIODICALS

Martin, Guy. “Secret Shame Dept.: The Lice Lady.” New Yorker, January 28, 2002. Available online at http://www.newyorker.com/archive/2002/01/28/020128ta_talk_martin (accessed April 11, 2008). This is a brief article about a woman in New York City who specializes in removing head lice from infested children. It offers an interesting commentary on the social embarrassment related to lice.

Nagourney, Eric. “Remedies: Researchers Devise New Weapon for Head Lice.” New York Times, November 7, 2006. Available online at http://www.nytimes.com/2006/11/07/health/07reme.html?_r=1&adxnnl=1&oref=slogin&adxnnlx=1207983942-MstifzAXSWAkVQov04eGlQ (accessed April 11, 2008).

Wade, Nicholas. “In Lice, Clues to Human Origin and Attire.” New York Times, March 8, 2007. Available online at http://www.nytimes.com/2007/03/08/science/08louse.html (accessed April 12, 2008).

WEB SITES

Centers for Disease Control and Prevention (CDC). Parasitic Disease Information: Lice Infestation. Available online at http://www.cdc.gov/ncidod/dpd/parasites/lice/default.htm (accessed April 8, 2008).

Nemours Foundation. KidsHealth: Hey! A Louse Bit Me!. Available online at http://www.kidshealth.org/kid/ill_injure/bugs/louse.html (last updated September 2007; accessed April 12, 2008).