Head lice infestation

Head lice are generally uncomfortable, but typically do not constitute a serious condition. Itching may take 2–6 weeks to develop upon first infestation, and sooner in subsequent infestations. In Ethiopia, head lice appear to be able to spread louse-born epidemic typhus and Bartonella quintana. In Europe, the head lice do not appear to carry these infections. ==Transmission==

Head lice spread through direct contact of the head of an infested person with the head of a non-infested person. Head lice do not leap or spring as a means to transfer to their hosts; instead, they move by crawling. Transmission by indirect contact (e.g. sharing bedding, clothing, headwear, the same comb) is much less common. Pets are not vectors for head lice. Other lice that infest humans are the body louse and the crab louse (aka pubic lice). The claws of these three species are adapted to attach to specific hair diameters. Pubic lice are most often spread by sexual contact with an infested person. Body lice can be found on clothing and they are not known to burrow into the skin. ==Diagnosis==

The condition is diagnosed by finding live lice and unhatched eggs in the hair. Finding empty eggs is not enough. This is made easier by using a magnifying glass or running a comb through the child's wet hair, the latter of which is the most assured method of diagnosis and can be used to monitor treatment. In questionable cases, a child can be referred to a health professional. However, head lice infestation is commonly overdiagnosed, with extinct infestations being mistaken for active ones. Infestations are only considered extinct if nits are more than 0.25 inches away from the scalp and nymphs and adult lice are absent. As a result, lice-killing treatments are more often used on non-infested than infested children. The use of a louse comb is the most effective way to detect living lice. With both methods, special attention should be paid to the area near the ears and the nape of the neck. The use of a magnifying glass to examine the material collected between the teeth of the comb could prevent misdiagnosis. The presence of nits alone, however, is not an accurate indicator of an active head louse infestation. Generally, white nits are empty egg casings, while brown nits may still contain viable louse larvae. One way to determine the nit is to squeeze it between two fingernails; it produces a characteristic snapping sound as the egg bursts. Children with nits on their hair have a 35–40% chance of also being infested with living lice and eggs. If lice are detected, the entire family needs to be checked (especially children up to the age of 13 years) with a louse comb, and only those who are infested with living lice should be treated. As long as no living lice are detected, the child should be considered negative for head louse infestation. Accordingly, a child should be treated with a pediculicide only when living lice are detected on their hair (not because they have louse eggs/nits on their hair and not because the scalp is itchy). ==Prevention==

Examination of the head at regular intervals using a louse comb enables the early diagnosis of louse infestation. Early diagnosis makes treatment easier and reduces the possibility of infesting others. In areas and times when louse infestations are common, weekly examinations of children, especially those aged 4–15 years, carried out by their parents, will aid in control. Additional examinations are necessary if the child has come into contact with infested individuals, if the child frequently scratches their head, or if nits suddenly appear on the child's hair. Clothes, towels, bedding, combs, and brushes, which came in contact with the infested individual, can be disinfected either by leaving them outside for at least two days or by washing them at 60 °C (140 °F) for 30 minutes. This is because adult lice can survive only one to two days without a blood meal and are highly dependent on human body warmth. ==Treatment==

There are several treatments effective for head lice. These methods include combs, shaving, medical creams, and hot air. Medical creams usually require two treatments a week apart. There is no evidence of pesticide resistance. Abametapir was approved for medical use in the United States in July 2020. Resistance to several commonly used treatments is increasing worldwide, with patterns of resistance varying by region. Head lice have demonstrated resistance to permethrin, malathion, phenothrin, and carbaryl in several countries around the world. A 2012 review of head lice treatment recommended against the use of tea tree oil for children because it could cause skin irritation or allergic reactions, because of contraindications, and because of a lack of knowledge about the oil's safety and effectiveness. Other home remedies, such as putting vinegar, isopropyl alcohol, olive oil, mayonnaise, or melted butter under a shower cap, have been disproven. Environment After treatment, people are often instructed to wash all bedding and vacuum all areas the head may have been, such as car seats, coat hoods, and sofas, but this is not always necessary, since adult lice will die within 2 days without a blood meal, and newly hatched lice die within minutes of hatching. Outbreak management In addition to environmental management, an outbreak of head lice infestation requires synchronous treatment of all individuals who are infested and evaluation of those who have been exposed or are suspected of having head lice. Synchronous ovoidal dimethicone treatment has been shown to manage and terminate outbreaks effectively, and a single treatment is likely sufficient. Other treatment methods can be repeated 8–10 days after the initial treatment and may sometimes require a third treatment. Outbreak status and treatment effectiveness can be monitored using the wet combing method. ==Epidemiology==

The number of cases of human louse infestations (or pediculosis) has increased worldwide since the mid-1960s, reaching hundreds of millions annually. It is estimated between 1 and 20% of specific groups in Europe are infected. Lice infestation during that same period was more prevalent than chickenpox. The United Kingdom's National Health Service reports that lice have no preference for any type of hair, be it clean, dirty, or short. The number of children per family, the sharing of beds and closets, hair washing habits, local customs and social contacts, healthcare in a particular area (e.g. school), and socioeconomic status were found to be factors in head louse infestation in Iran. Other studies found no relationship between frequency of brushing or shampooing. The California Department of Public Health indicates that chronic head lice infestation may be a sign of socioeconomic or family problems. Children between 4 and 13 years of age are the most frequently infested group. In the U.S., African-American children have lower rates of infestation. But these children may have nits that hatch and the live lice could be transferred by head contact to other children. ==Stigma==

Head lice infestations are notably common, as is the stigma associated with those who experience infestations. Such stigma is even evidenced in the English language as the term "lousy", an adjective that describes something as very poor, bad, or disgusting. Misperceptions of those infected with head lice include that it is associated with low socioeconomic status, poor hygiene, unhealthiness, immigration status, and homelessness. Though these negative beliefs are unfounded, they can lead to consequences for both the caregivers and the affected individual, such as social exclusion and isolation from peers, victim-blaming, caregiver strain, inappropriate or unsafe treatment practices, and missed work or school. Public-health implications Over-treatment or mismanagement of head lice, which can be driven by stigma, has important implications at the level of the individual and community. Though evidence-based guidelines from the CDC, American Academy of Pediatrics (AAP) and National Association of School Nurses (NASN) all recommend discontinuing "no-nit" policies in schools (meaning that a child does not need to be free of nits before returning to school), 80 percent of schools in the United States still maintain stringent policies that prevent children with infestations from attending. ==Society and culture==

• "To a Louse" (on a lady's bonnet). Perhaps the most widely known cultural reference to pediculosis capitis is in a noted poem by Robert Burns. ==Other animals==

Lice infestation in general is known as pediculosis, and occurs in many mammalian and bird species. Lice infesting other host species are not the same organism as that which causes head lice infestations in humans, nor do the three louse species which infest humans infest any other host species. ==References==