What’s new in the head lice arsenal?

Each year, an estimated 6 million to 12 million lice infestations occur among children aged 3 to 11 years and cost an estimated $1 billion annually in treatment, lost wages, and other collateral damage. As the summer months approach and the likelihood of transmission at summer sporting events and campouts looms, the American Academy of Pediatrics (AAP) has updated its clinical guidance report on head lice management in the May 2015 issue of Pediatrics.

More: Head lice myths, facts, and treatments

Life infestations know no socioeconomic boundaries, and occur most often in children because of the frequency of head-to-head contact. “Lice are a nuisance or annoyance. They do not jump, they crawl, and direct, generally prolonged contact is needed for someone to get an infestation from another child or adolescent,” says Cindy Devore, MD, FAAP, lead author of the new AAP guidance and a member of AAP’s Council on School Health and Committee on Infectious Diseases. “Anyone can get head lice. They are not life-threatening or disease carrying and in most areas of the [United States] will respond to adequate treatment with common over-the-counter (OTC) medicines following exact manufacturer instructions.”

Devore says none of the original recommendations from the 2010 version of the same guidance have changed, but that 2 new medications are now available. The guidance also reiterates the AAP’s previous stance on school rules regarding children with lice and lice screenings. Children who have been found to have nits or an active infestation should be allowed to remain in school, be treated at home, and return to school without exclusion, according to the AAP clinical report.

In regard to the 2 new medications, Devore notes that topical spinosad and topical ivermectin use are not recommended in infants aged younger than 6 months, but can be used for children and adolescents aged 6 months and older. Retreatment may not be necessary with these newer prescription medicines, Devore adds, but should live lice be found, parents should check with their pediatricians for retreatment guidance.

“Parental surveillance, especially following sleep-away camps or slumber parties, is one of the best ways to detect and treat cases early and decisively. However, in regions with known resistance to OTC medicines or in children or adolescents who upon discussion with their pediatricians appear to have failed conventional OTC treatment, prescription is available,” Devore says. “No child or adolescent should be excluded from school for live lice or nits.”

Although prevention is key in many situations, there are no sure-fire methods to prevent lice infestation. Daily bathing is not an effective solution because lice can survive submerged in water for 20 minutes and their eggs are not susceptible to pesticides. The recommendation, rather, is for regular surveillance so infestations can be caught early and to avoid spreading lice to others.

Lice are not responsible for the spread of any disease, although excessive scratching as a result of an infestation could lead to a bacterial infection. Also, lice can be spread among anyone regardless of socioeconomic status or hygiene practice. Yet despite this knowledge, infestations still carry with them a stigma and oftentimes social ostracization, the AAP notes in its new report.

Adult lice-or head louse-are roughly the size of a sesame seed (2-mm to 3-mm in length) with 6 legs and a tan to grayish-white color. Female adults can live 3 to 4 weeks and lay up to 10 eggs in a single day. The eggs attach themselves along hair shafts within 4 mm of the scalp with a glue-like substance created by the louse. Viable eggs can be difficult to see because of pigmentation that camouflages the eggs against the hair, but eggs can usually be detected along the border of the posterior scalp.

Eggs take between 8 and 12 days to hatch depending on the climate, and the nymph then passes through 3 stages over the next 9 to 12 days until it reaches adulthood. The female louse can lay eggs about 1.5 days into adulthood. Empty egg casings-nits-are left behind as the nymphs hatch and are easier than eggs to detect because they appear white against dark hair. Lice can’t survive for more than a day without a host, and eggs can’t hatch at temperatures lower than what is found near the scalp.

Louse feed on humans by injecting small amounts of saliva into the scalp at the hair shaft, injecting vasodilators and anticoagulants so that it can suck small amounts of blood every few hours. Pruritus results from sensitivity to components of the saliva, but can take 4 to 6 weeks from the beginning of an infestation for this symptom to develop.

Lice are most frequently spread by head-to-head contact. They can only crawl, not hop or jump, although the AAP notes that there have been reports of static electricity produced by combing ejecting an adult louse from a scalp to a distance of 1 meter away. Most often, lice infestations spread through brushes, hats, and combs, although lice found on combs are likely to be injured or dead, says the AAP.

Physicians have been somewhat removed from the battle against lice infestations, says the AAP, because parents and non-healthcare personnel are often the ones to make the diagnosis of the infestation, and effective OTC remedies are readily available.

“However, the potential for misdiagnosis and the resulting improper use of pediculicides and the emergence of resistance to both available and newer products, many without proof of efficacy or safety, call for increased physician involvement in the diagnosis and treatment,” says the AAP in its new report.

NEXT: Diagnosing an infestation

Diagnosis can be made by a visual examination for nits, nymphs, or adult lice. It may be easier to detect lice by using a lice comb, or even lubricants, which can slow the movement of the quick-crawling lice.

Tiny eggs are most often spotted at the nape of the neck or behind ears, and eggs or nits will be firmly attached to the hair shaft. Take care not to confuse lice or their eggs with other debris found in hair, the AAP cautions. “Many presumed ‘lice’ and ‘nits’ submitted by physicians, nurses, teachers, and parents to
a laboratory for identification were found to be artifacts, such as dandruff, hairspray droplets, scabs, dirt, or other insects,” the AAP says.

First-line treatments for lice infestation include permethrin and pyrethrins, but those medications belong to a chemical class to which there is now increasing resistance. Second-line treatments, lindane and malathion, also have limitations, specifically related to safety concerns about flammability and noxious odor, says the AAP report. Benzyl alcohol and spinosad both have been recently approved by the US Food and Drug Administration (FDA) for the treatment of lice infestation. Up to 2 treatments with either agent is effective, the AAP says, but in all these treatments, the short generation time of the louse and exposure to all life stages are increasing resistance, so new therapies are needed.

Ivermectin is an oral medication used to treat nematode infections, and the drug is now approved by the FDA for combating louse and scabies infections when conventional methods have failed. Ivermectin also has been shown to be effective against permethrin-resistant head lice in vitro using 2 oral doses of 400 μg per kilogram of body weight spaced 1 week apart, reports the AAP. The academy says ivermectin would be useful in delaying emerging resistance, or managing existing resistance to other traditional treatments, and that it could be developed as a topical formulation to avoid systemic effects. Pruritus was the most common adverse effect of ivermectin treatment in recent studies, and in 1 trial, 94.9% of participants were louse-free after the first day of an oral ivermectin dose.

More: When fever and rash become emergent

Ivermectin primarily targets glutamate-gated chloride ion channels. Permethrin and pyrethrins act by binding to voltage-gated sodium channels, and widespread resistance to permethrin has been reported. Even with nit combing as an adjuvant therapy, permethrin has failed to reach efficacy of 50%, says the AAP, whereas ivermectin was at least 70% effective even after 2 weeks. With the absence of adverse effects in recent studies, the AAP says topical ivermectin is a novel treatment useful in cases of resistance and it is highly effective when administered in a topical formulation within 24 hours, with most patients remaining louse-free for 2 weeks after a single treatment and without the need for nit combing.

Although there are many treatments available, including the new medications, the AAP says pediatricians should stick with what has worked. Without demonstrated resistance in the community, the AAP recommends using OTC medications containing 1% permethrin or pyrethrins as first-line treatment for active infestations. Chronic problems are best handled through regular checks by parents and an OTC pediculicide followed by wet combing and possibly reapplications at days 9 and 18.

Areas experiencing resistance against the traditional treatments can reach into the new arsenal of medications to fight lice infestation, such as spinosad or topical ivermectin.

Ideal treatments of lice infestation should be affordable, accessible, effective, and easy-to-use, says the AAP. Additionally, treatment should not be initiated unless there are living lice present.

NEXT: A review of current treatments

The clinical report lists these current available treatments for head lice:

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• Permethrin (1%)-The most studied treatment, this pediculicide is the least toxic to humans. Marketed as a crème rinse under the brand name “Nix,” the product is applied to damp, shampooed hair, left on for 10 minutes, and then rinsed off. It leaves a residue that kills emerging nymphs from eggs that were not killed during the initial application. A second application is best applied on day 9 following the initial application.

• Pyrethrins plus piperonyl butoxide-Manufactured from chrysanthemum extracts, pyrethrins are formulated with piperonyl butoxide, marketed under the brand name “Rid.” It is available in shampoo or mousse formulations and applied to dry hair, left on for 10 minutes, then rinsed off with no residual activity.

• Malathion (0.5%)-An organophosphate (cholinesterase inhibitor) 0.5% malathion, marketed as “Ovide,” was taken off the market twice for adverse events related to application time, flammability, and odor, but was reintroduced in 1999. It is available by prescription only as a lotion that is applied to dry hair, left to dry on the hair, then washed off 8 to 12 hours later. There is some resistance to malathion, but it has higher cure rates after 1 application than pyrethrins or permethrin. The product may need to be reapplied 7 to 9 days after the initial application, and patients must be cautious about flammability caused by its high alcohol content. Safety of using malathion is not established in children aged younger than 6 years, and it is contraindicated for infants aged younger then 24 months.

• Benzyl alcohol 5%-Marketed as “Ulesfia,” benzyl alcohol was approved by the FDA in April 2009 to treat head lice in children aged older than 6 months. It kills the lice by asphyxiation, applied to dry hair to saturate the scalp and length of hair for 10 minutes and repeated 9 days after first application. It is available only by prescription.

• Spinosad (0.9% suspension)-Marketed as “Natroba,” spinosad was approved by the FDA for topical use in children aged 6 months and older, but it is contraindicated for those younger because it contains benzyl alcohol. The compounds in this medication are derived from natural fermentation from soil bacterium Saccharopolyspora spinosa. The medication appears to be both ovicidal and pediculicidal, damaging the developing nymphs. Spinosad has been proven in clinical trials to be roughly twice as effective as permethrin. Spinosad is available by prescription and should be applied to dry hair by saturating the scalp and working outward to the ends of the hair, then rinsed
after 10 minutes. A second treatment is given at 7 days if live lice are seen. This treatment has not been established in children aged younger than 4 years.

• Ivermectin (0.5%)-Marketed as “Sklice,” ivermectin is an anthelmintic agent approved by the FDA in 2012 as a lotion to combat lice infestations for children aged 6 months and older. This medication increases the chloride ion permeability of muscle cells, resulting in hyperpolarization, paralysis, and death of the lice. Topical ivermectin is available by prescription in a lotion formulation that is applied to dry hair and scalp, and rinsed after 10 minutes. Only 1 application is required because the medication works by paralyzing pharyngeal muscles within the eggs, resulting in nymphs that are unable to feed after hatching.

• Lindane (1%)-Lindane is no longer recommended by the American Academy of Pediatrics.

• Permethrin (5%)-Although it is not approved by the FDA for the treatment of lice infestations, permethrin 5% can be given under prescription for the treatment of scabies in infants aged younger than 2 months. It has been used for the treatment of head lice that seem to be resistant to other treatments, AAP notes.

• Crotamiton (10%)-Also not approved by the FDA for lice management, this product can be used under prescription for scabies. However, 1 study showed it was effective against lice when applied to the scalp and left for 24 hours. Safety for children has not yet been established.

• Ivermectin (oral)-Oral ivermectin, is marketed as “Stromectol,” is an anthelmintic agent that is structurally similar to macrolide antibiotic agents but without any antibacterial properties. To be effective against lice, a single oral dose of 200 mcg/kg is given, then repeated in 10 days. A single oral dose of 400 mcg/kg repeated after 7 days has shown to be more effective than 0.5% malathion lotion. However the medication should not be given to children weighing less than 15 kg because of a higher risk of adverse drug reactions involving crossing of the blood/brain barrier and neural transmission interruption.

• Sulfamethoxazole-trimethoprim-An oral antibiotic marketed as “Septra,” this medication is not currently approved by FDA for treating lice, but it is believed to kill symbiotic bacteria in the gut of the louse and maybe even have a direct toxic effect. Rare but severe allergic reactions have occurred in small-scale trials.

• Essential oils-Combinations of oils such as anise, ylang-ylang, and coconut oils have been combined into products some researchers say are as effective as permethrin products against lice, but natural products also are not required to meet FDA efficacy standards. Without more data available about possible adverse effects, the AAP recommends avoided essential oils in infants and young children.

• Occlusive agents-Items such as mayonnaise, butter, and oils are applied to suffocate lice but have not been thoroughly evaluated in clinical trials for effectiveness against lice.

• Desiccation-A custom-built device called AirAllé from a company in Utah uses a single 30-minute application of hot air to desiccate the lice. Early testing revealed a 100% mortality rate among eggs and 80% mortality rate among nymphs. However, the machine is expensive and requires special operator training. A regular hair dryer would not have the same effect, the AAP cautions, and could actually increase the spread of a lice infestation.

• Manual removal-There is little data on the benefits of manual removal, but AAP acknowledges the “obvious benefit” of not using pesticides on children. “There is an obvious benefit of the manual removal process that can allow a parent and child to have some close, extended time together while safely removing infestations and residual debris without using potentially toxic chemicals on the child or in the environment,” the AAP report states. “Furthermore, manual removal of nits will help to diminish the social stigma and isolation a child can have in the school setting. Individuals also may want to remove nits for aesthetic reasons or to decrease diagnostic confusion.”

Fine-toothed “nit combs” are sold commercially and make manual removal easier. Combing is most easily accomplished on wet hair, the report notes. Products such as vinegar are sometimes used to loosen the “glue” that the louse uses to attach its eggs to the hair shaft, but no clinical evidence supports the use of such products. Additionally, hair length is not related to the likelihood of infestation or effective treatment against nits, the AAP says.

All members of a household in which lice infestation has been found should be checked and treated, if necessary. It is also good practice to treat any individuals who share a bed with a person experiencing an infestation whether or not any lice are found. Changing pillowcases and cleaning items that touched an infested person’s head 24 to 48 hours prior to treatment help control the spread of infestation or reinfestation.

The report notes that washing, soaking, or drying items at temperatures above 130°F will kill lice, plus vacuuming is effective on carpeting and fabric surfaces. Items that are possibly infected but that cannot be laundered also may be placed in a sealed bag for 2 weeks, during which time any hatched nymphs or adult lice will die without the ability to feed. Exhaustive cleaning is not beneficial in combatting a louse infestation, the AAP adds.

NEXT: Has school management changed?

In regard to school management, the new guidance reiterates its assertion that children should not be excluded from school or school events because of lice, and that screening for nits is not a good indicator of infestation. In fact, such screenings have been shown to have little effect on the incidence of head lice and are not cost effective. For example, the AAP highlights a study in which, of 1729 children screened for head lice, only 31% of the 91 children with nits had an active live lice infestation. Another 18% with nits developed an infestation within 2 weeks of observation.

“Because of the lack of evidence of efficacy, routine classroom or schoolwide screening should be discouraged,” the AAP says. “Although children with at least 5 nits within 1 cm of the scalp were significantly more likely to develop an infestation than were those with fewer nits (32% vs 7%), only one- third of the children at higher risk converted to having an active infestation. School exclusion of children with nits alone would have resulted in many of these children missing school unnecessarily.”

Additionally, says the AAP, lice infestations have low contagion in classrooms. Between that and the fact that children who are diagnosed have likely been infested a month or more by the time of diagnosis, students diagnosed with a lice infestation should remain in class but close head contact with others should be discouraged. Alerting an entire classroom of parents also should be questioned, the AAP says, citing sentiments from experts that “because of the relatively high prevalence of head lice in young school-aged children, it may make more sense to alert parents only if a high percentage of children in a classroom are infested.”

“No-nit” policies that exclude children from school activities until all nits are removed also should be abandoned according to many health professionals, the report says. “International guidelines established in 2007 for the effective control of head lice infestations stated that no-nit policies are unjust and should be discontinued because they are based on misinformation rather than objective science,” the report states. “The American Academy of Pediatrics and the National Association of School Nurses discourage no-nit policies that exclude children from school. However, nit removal may decrease diagnostic confusion, decrease the possibility of unnecessary retreatment, and help to decrease the small risk of self-reinfestation and social stigmatization.”