Human Lice Control
These human-infesting biting insects receive their common names from the areas they typically latch on to. Remember: lice infestation of any area of the body is a medical problem, not just a pest control problem. The body louse is a vector of human diseases such as typhus, relapsing fever, and trench fever. The other varieties of lice don’t transmit diseases, but they’re still highly contagious and problematic. Lice are found all over the world. There are three main varieties of human-infesting lice:
- The head louse measures 1/8 inch long and has a flat, elongate body. It attaches to people’s heads and attaches its eggs (nits) to hair.
- The body louse measures 1/8 inch long and has an elongate, flattened body. It infests clothing and feeds on adjacent body areas to feed. Body lice glue their nits to clothing fibers.
- The crab/pubic louse is 1/16” long, with a crablike body that is flattened but broadly oval in form. It occurs primarily where flat hairs are present (pubic region, armpits, eyebrows, beards), and attaches nits to body hairs.
APPEARANCE AND BEHAVIOR
Head lice live on their hosts permanently. Each female lays 50 to 100 oval nits, which are pearly white and 1/32” long. Each egg, or nit, is individually securely cemented to a head hair near the scalp. Nits require high relative humidity and warmth in order to develop and hatch.
Nits hatch in 5 to 10 days. Growing lice undergo 3 nymphal instars. The life cycle (nit to nit) takes place over about 3 weeks. Adults live for about 23 days. Head lice can survive no more than 48 hours when detached from the host. They are most commonly found above the ears and on the back of the scalp. Sometimes they’ll infest the entire scalp, but that’s less common. In some rare cases, head lice may even infest other body hairs such as in the eyelashes. Head lice are commonly transmitted by the direct contact of 2 heads, or by combs, hair brushes, or hats. Lice are always seeking a host, so if they fall off of one, they’ll try to find another.
Body lice occur primarily in the clothing, especially clothing in contact with the body. They move to adjacent body areas to feed. The female lays about 200 oval nits, which are pearly white and 1/32” long. Females lay 5 to 8 nits per day, usually during periods of host inactivity. Each nit is individually securely cemented to a clothing fiber and only occasionally to body hair.
Body lice tend to lay their nits in large numbers along the seams of underwear and in places where clothing contact the body. Look for nits on clothing near the neck, shoulder, armpit, waist, and the crotch of trousers. Body lice prefer wool clothing. When feeding, body lice usually retain their hold on the adjacent clothing. They’ll only occasionally crawl onto the body. Body lice are commonly transmitted when an infected person shares their clothing or bedding with someone else.
Crab/pubic lice live continuously on the host. The female lays 2 to 3 whitish nits per day, for a lifetime total of 15 to 50 nits. Each nit is firmly cemented to a coarse hair near the skin. Nits hatch in 7 to 8 days. Nymph lice can begin feeding within 1 to 2 hours after hatching. The first instar nymph feeds off and on for 5 to 6 days and then molts. The second instar requires 9 to 10 days, and the third instar 13 to 17 days. The life cycle (nit to nit) requires about 5 to 6 weeks.
Adults live for about 15 to 25 days. Crab lice can survive no more than 24 hours when detached from a host. Once a louse settles it does not move much. They feed off and on for several hours at a time and defecate blood and body wastes while feeding. Crab lice are transmitted by intimate or sexual body contact. They are found primarily in the public and perianal areas.
HUMAN LICE CONTROL AND PREVENTION
Control on human host infested with human lice involves the following steps:
- Use a prescribed shampoo (head) or lotion (body and crab/pubic) or over-the-counter preparations containing insecticides. Follow the instructions on the product label.
- For head and crab/pubic lice, two or more treatments are required, because not all eggs/nits are killed with the first application. The timing of the second treatment allows for the hatching of any viable nits.
- Because of secondary infections of the skin caused by scratching, you may also require an antibiotic therapy.
- Hot cycle wash and dry all the clothing, bedding, and towels used by infested individuals. You should also follow this procedure for individuals who have slept in the same bed with an infested person.
- Non-infested people should not share towels, combs, hair brushes, hats, clothing, and similar items with infested people. Note that if hot cycle washing is not available, boil clothing and bedding for at least 10 to 15 minutes.
The control of head, body, and crab/pubic lice is a medical problem. Lice spend essentially all of their time on the host (head and crab/pubic) or host’s clothes (body). They can only survive for a short time when detached from the host or host’s clothing. Lice, which are easily dislodged or drop from their host, are frail and unlikely to infest a new host.
A pest management professional should not be called upon to apply insecticides to control lice indoors or to treat infested persons. Plunkett’s Pest Control specialists do provide practical information to those requesting it. Instead, you need to contact your doctor to receive direct care next steps for eradication of your lice infestation.