Head lice hysteria: Balancing interventional risk with benefit
The recently published American Academy of Pediatrics Clinical Report on Head Lice comes at an opportune time for pediatric practitioners.
Each new school year brings with it a “pseudo-epidemic” of head lice, as schools focus on their newly corralled charges.
Although head lice infestation is not associated with real risk (pruritus and secondary impetigo excepted), it often induces hysteria in parents and communities. Many consider lice infections an affront to their cleanliness, with attendant disgust and embarrassment clouding parental and school judgment regarding the appropriate response to this bothersome condition. Such behavior generates significant societal costs. In 1998 an estimated 12 to 24 million lost school days occurred as a result of “no-nit” policies; in addition approximately $1 billion was spent when both direct and indirect costs of medication and lost parent work days were considered.
The latest AAP report by Frankowski & Bocchini offers a comprehensive overview of diagnostic and therapeutic issues surrounding head lice. It also provides a common sense approach to public health concerns regarding increasing therapeutic resistance that has been documented both here and in other industrialized nations.
Head lice have coexisted with humans since antiquity, and the organism has proven quite capable of eluding eradication. In remote areas of Central & South America, almost everyone is infested. In the United States, children 3-12 years of age are most commonly affected, and in 1997 it was estimated that 6-12 million infections occur yearly. All socio-economic groups are affected, and hair length does not seem as important to infection load as does frequency of brushing; those with daily brushing routines often have less organisms.
Familiarity with the louse life cycle is important in designing treatment strategies. The sesame-sized (2-3mm) tan-gray adult feeds in a vampire-like fashion, injecting saliva with anticoagulant properties into the scalp and then sucking blood every 2-4 hours; this induces sensitization and sometimes severe pruritus. The female lives up to 4 weeks and produces approximately 10 eggs per day. The eggs are attached within 4 mm of the scalp, and hatch in 7-12 days (average 8.5 days). A viable egg is darker than the empty white to opalescent nit casing. Some consider all eggs nits, while others label structures containing viable organism eggs, reserving the term nit for an empty casing. Hatched lice cannot jump, but do move quickly on dry hair, and can be ejected up to 1 meter if hair brushing induces conducive electrostatic forces. Transmission generally occurs as a result of direct contact with an infected head. While fomites can spread disease, this is less likely; one study showed that only 4% of pillowcases used by infested individuals contained live lice. Lice generally do not survive for more than a day away from a scalp, and the eggs cannot hatch at room temperature.
The AAP report emphasizes that the best method of diagnosis entails finding a live louse on the head while acknowledging that this is often difficult. The presence of live eggs within one centimeter of the scalp is also diagnostic. Methods to improve diagnosis include examining wet or lubricated hair with a fine-toothed comb, as lubricating the hair decreases louse mobility; in addition focusing on the nape of the neck or behind the ears increases yield. They emphasize that dandruff, empty egg casings (nits), and other hair debris must not be confused with a live egg.
The most powerful messages from the recent recommendations concern prevention and therapy. Given that most infested children have already been afflicted for at least a month; experts feel it makes no sense to keep children home from school after diagnosis.
"No-nit” policies have not been shown to effectively decrease the spread of head lice, and generate inappropriate and significant lost school and work days for affected families. Following diagnosis, the child’s family should be notified and treatment recommended, but the child should remain in school, given the low contagion documented within classrooms. Children should not share combs, brushes or hats. A knowledgeable school nurse can be helpful in screening children if requested by a parent. Any person who has shared a bed with the index case should be empirically treated, and all family members should be evaluated. Those who have had direct head to head contact with the index case also warrant evaluation, and many schools send out notification to all families when a case of pediculosis is documented. The use of “school-alert “letters has not been studied and is controversial, but may help to increase awareness while at the same time providing reassuring factual information. Fomite transmission is less likely than direct contact, but it is appropriate to clean hair care items and bedding of the infested individual. Any items that have been in contact with the head of the infested person within 24-48 hours before treatment could theoretically transmit disease, and clothing, head gear, furniture, carpets and rugs can be considered for cleaning at temperatures greater than 130degrees F. Furniture may be vacuumed.
The ideal treatment would be safe, effective, easy to use and inexpensive. Although resistance to various agents has been documented, insufficient comparative trials utilizing uniform inclusion criteria are available to define one clearly superior agent. Resistance is also a “moving target,” and appears to occur in any chemical agent if it is used for a long-enough period. A 2001 Cochrane analysis addressing louse therapy was subsequently withdrawn in 2007, in recognition of the incomplete nature of the discussion on resistance. The optimal therapy for any one area will depend on local resistance patterns. Given the lice life cycle and average incubation period of 8.5 days, reapplication at 9 days is sensible, and some recommend three treatments (days 0, 7, and 13-15) to ensure complete eradication. No clear benefit has been shown with products marketed to loosen nits/eggs from the hair shaft.
FDA approved products include permethrin 1%, pyrethrins such as RID & Pronto, malathion (Ovide) and Benzyl alcohol 5% (Ulesfia). The FDA has issued a health advisory regarding lindane, which is not recommended for first-line use due to its potential neurotoxic effects. One percent permethrin lotion or pyrethins (OTCs) can be utilized as first-line therapy when resistance is not a concern. Permethrin 1% is thought to be the best-studied pediculocide in the United States, and the least toxic. A cream rinse formulation (Nix) can be applied to towel-dried hair previously washed with a non-conditioning shampoo, and then rinsed off after 10 minutes. A residue remains on hair which can kill emerging nymphs.
Unfortunately, neither permethrin nor pyrethrin products are strongly ovicidal, and therefore repeat treatments are recommended. In contrast, malathion (Ovide), an organophosphate has high ovicidal activity. This advantage must be weighed against its flammable nature and it is contra-indicated in children younger than 24 months.
A recently FDA approved prescription product , benzyl alcohol 5% (Ulesfia), kills lice by asphyxiation A 75% cure rate was noted in two studies 14 days after application. The drug is not ovicidal. Another non-FDA approved suffocation agent, Nuvo lotion, consists of Cetaphil lotion, and can be applied, dried, and left on overnight.
The AAP guidelines give credence to the use of nonchemical options in families who want to avoid chemicals, or for whom chemical options have failed. These include twice weekly combing of wet hair with fine-toothed combs, and removal of live insects and eggs. Other options include occlusive methods utilizing products such as petrolatum. These methods are messier and time-consuming, but more acceptable to some families. Essential oils are also available, often in combinations (eg. anise, ylang-ylang & coconut oils with alcohol (Clean 1-2-3)), but efficacy has not been well documented for such products. Though not mentioned in the report, a topical eucalyptus-clove oil combination shows promise and appears to have fumigant as well as topical pediculocidal activity; thus lice may be killed by the “fumes” of the volatilized oils and thus direct contact may not be necessary, making the application process less onerous. The report also reviews the characteristics of other non-FDA approved options, including oral trimethoprim-sulfamethoxizole and ivermectin, but considers them second-line therapies.
The new clinical report provides practitioners and families with a common-sense, flexible approach to therapy, and reinforces the need for health care providers to weigh “risk-benefit” ratios when considering interventions for this benign but bothersome affliction.
Take home points:
- Healthy children with head lice should NOT be excluded from school. “No-nit” policies should be eliminated.
- 1% permethrin or pyrethrins can be utilized as first-line therapy, unless resistance has been documented in the community
- Reapplication is recommended; repeat at 9 days, or utilize 3 treatment therapy (day 0, 7, 13-15 )
- Options for resistant areas or cases include “wet-combing”, or an occlusive agent such as petrolatum or Cetaphil lotion.
- Other more expensive options for resistance include benzyl alcohol 5% in children older than 6mos, and malathion in those 2 years or older
For more information:
- Frankowski BL & Bocchini JA. Pediatrics. 2010;126:392-403.
- Hansen RC. Clin Pediatr. 2004;43(6)523-527.
- Gratz NG. Human Lice: Their Prevalence, Control, and Resistance to Insecticides – A review, 1985-1997. Geneva, Switzerland: World Health Organization , WHO Pesticide Evaluation Scheme; 1997.
- Burgess If, Pollack RJ, Taplin D. Cutting through controversy: Special report on the treatment of head lice. In: The Treatment of Head Lice. Englewood, Co Postgraduate Institute for Medicine; 2003:3-13.
- Jones KN. Clin Infect Dis. 2003;36(11):1355-1361.
- Burgess IF. Adv Parasitol. 199536:271-342.
- Dodd CS. Cochrane database Syst Rev. 2007;(4)CD001165.
- Meinking TL. Pediatric Dermatol. 2010;27(1):19-24.
- Choi HY. J Med Entomol. 2010 May;47(3):387-91.