NPIPM:Pediculus capitis
Authors: Ashley Mueller, Buyung Hadi
Identification
Head lice are wingless and flattened in appearance. Adults are relatively small, and they are about 1/10 of an inch long. They have hook-like claws at the end of each leg that they use to attach to hair shafts. Head lice do not jump or fly, but they move very quickly and tend to avoid light. Head lice eggs are called nits, and they are found at the base of the hair shaft. If they are found more than 1/2-inch away from the base of the hair shaft, usually the nits have either hatched or died.
Habitat
Head lice are found all over the world. Head lice infestations are often found in homes, daycares, schools, and other public settings. They are highly communicable and spread easily with close contact.
Life Cycle and Seasonal History
Adult females lay eggs onto hair shafts near the scalp, typically on the nape of the neck and behind the ears. The sticky eggs hatch in about one week. Immature head lice, called nymphs, are very mobile, and over approximately three weeks, they molt to become adults. Adult head lice live for about four weeks, but they are unable to survive off a host for more than one or two days.
Human Interaction and Urban Impact
Although head lice are not economically important, they can be a health concern. Head lice feed on human blood, and they use piercing-sucking mouthparts to withdraw a meal from the host. Infestation by head lice is called pediculosis. Signs of head lice include itching of the scalp and restlessness. Some individuals may develop an allergic reaction to louse saliva, which is usually itching and general discomfort. Bacteria normally present on the skin surface can infect the wound inflicted by the bite. Head louse is not a known vector to any disease.
Head lice can occur on anyone; they do not distinguish between dirty and clean individuals. Head lice are highly communicable, and they spread primarily through the sharing of combs, brushes, and personal clothing items upon which hair with attached nits may have shed. Head lice do not feed on pets or other animals.
Prevention and Management Approaches
To prevent head lice, avoid hair-to-hair contact with others. Not sharing combs, brushes, hats, and other personal clothing items will control the spread of head lice. At schools or daycares items that touch the hair, such as hats, should be placed in a wooden or metal cubby. If a cubby is not available, these items should be stored in a plastic bag. Inspect children regularly for the presence of head lice or nits, starting at the back of the neck and moving forward while parting the hair. Using a good light and a magnifying glass is helpful. Checking others in the family, even if they are not displaying any symptom, is a good prevention practice. Educate family members about how head lice can spread from person to person.
If an infestation is confirmed, wash and dry clothing items, bed linens, and other items used or worn by the person with head lice by using a hot water (130oF) laundry cycle and a high heat drying cycle. Vacuum the floor and furniture carefully, and dispose of the vacuum bag when finished. Non-washable items should be placed in plastic bags and stored in a freezer for two weeks.
Removal of nits and immature and adult lice is important in managing an infestation. Nit combs or cat flea combs are designed to remove lice and eggs, and they can be purchased from pharmacies or online. Eggs can hatch as many as 10 days after they are laid, so hair should be combed daily for two weeks after the last live head louse is observed.
There are shampoos, creams, and lotions available on the market to control head lice. If a pediculicide (insecticide against lice) is used, directions should be followed precisely and extreme care should be taken. Many pediculicides are sold with nit combs.
Other Online Resources
For information regarding labels of chemical control options, please visit NPIC MAPL
