Persistent head lice following multiple treatments: evidence for insecticide resistance in Pediculus humanus capitis

Antiparasitic activity of ivermectin: Four decades of research into a "wonder drug"

Parasitic diseases still pose a serious threat to human and animal health, particularly for millions of people and their livelihoods in low-income countries. Therefore, research into the development of effective antiparasitic drugs remains a priority. Ivermectin, a sixteen-membered macrocyclic lactone, exhibits a broad spectrum of antiparasitic activities, which, combined with its low toxicity, has allowed the drug to be widely used in the treatment of parasitic diseases affecting humans and animals. In addition to its licensed use against river blindness and strongyloidiasis in humans, and against roundworm and arthropod infestations in animals, ivermectin is also used "off-label" to treat many other worm-related parasitic diseases, particularly in domestic animals. In addition, several experimental studies indicate that ivermectin displays also potent activity against viruses, bacteria, protozoans, trematodes, and insects. This review article summarizes the last 40 years of research on the antiparasitic effects of ivermectin, and the use of the drug in the treatment of parasitic diseases in humans and animals.

Prevalence of head lice (Pediculus humanus capitis) infestation among schools workers in the Eastern Region, Saudi Arabia

In a cross-sectional survey in February-May 2019, the prevalence of Pediculosis capitis with demographic data and the behavioral practices were investigated among 750 participants in the Eastern region of Saudi Arabia. Female participation was highly remarked with a percentage of 94.08% compared to that of male one about 5.91%. A deficiency of knowledge about lice infestation was noted especially among illiterate participants raised from their socio-economic levels (p-value = 0.001). Lice infestation reached higher rates in children aged less than 20 years with itching of the hair scalp. The obtained results revealed that 59.33% of the respondents believed that frequency of personal hygiene and washing of hair were the best methods for preventing the lice infestation. However, the treatment of lice infestation using anti-lice agents (p-value = 0.020) was preferred by 14.26% of participants. Although knowledge about the preventive tools for lice infestation (p-value 0.089) was not significantly associated with the experience of infestation but knowledge about the appropriate treatment to kill lice (p-value 0.020) and the wrong practices in the treatment of a head lice infestation were (p-value 0.005) significantly associated with the experience of infestation. Health programs and campaigns preventions are highly advised to increase the awareness of Pediculosis capitis with an effective strategic plan to control, manage, and prevent this disease.

High efficacy of a dimeticone-based pediculicide following a brief application: in vitro assays and randomized controlled investigator-blinded clinical trial

Background

Increasing resistance of head lice against neurotoxic agents and safety concerns have led to the search for treatment alternatives. Dimeticones with a physical mode of action are safe, and bear a reduced risk for the development of resistance.

Methods

We performed in vitro bioassays to assess pediculicidal and ovicidal activities of a new dimeticone-based product, and a randomized controlled clinical trial to assess efficacy, following 10 min application. Of 153 individuals screened, 100 participants with active head louse infestations were randomly assigned to treatment with either a dimeticone-based test product, or a 0.5% permethrin-based reference product (50 participants per group). Participants received two topical applications of either the test (10 min) or reference products (45 min) at days 0 and 7 or 8. Outcome measures included the efficacies of treatment and their safety, as well as global and local tolerability at baseline, and days 1, 7, and 10.

Results

After 10 min exposure, all lice treated with the dimeticone test product were classified as non-viable in the in vitro assay. Ovicidal activity after treatment of eggs with the dimeticone test product was 96.8%. In the clinical trial, 96 patients completed all study visits. In the full analysis set (FAS) population, on day 1 after one application, 98% of patients were cured in the test group, as compared to 84% cured in the reference group. All participants in both groups were free of head lice on day 10, following two applications (100% cure rate). In total, 42 adverse events (AEs) in 23 patients of both treatment groups were recorded, with the majority of AEs classified as mild.

Conclusions

We have shown a high level of pediculicidal and ovicidal activity, and clinical efficacy and safety, of a brief application of a new dimeticone-based product. The short application time and reduced risk for the development of resistance are key drivers for improved patients’ compliance.

Trial registration

EU Clinical Trials Register EudraCT 2016–004635-20. Registered 14 November 2016.

Pediculicide Resistance in Head Lice: A Survey

The head louse is an obligate human parasite. Evidence points to the growing resistance of head lice to nonprescription pesticides (eg, synergized pyrethrins, permethrin). To gather data, recent pharmacy graduates were surveyed about treatment failures and resistant lice. The response rate was 28.4%, with 173 of 609 surveys returned. One hundred and thirty-one pharmacists provided information that they had gathered during counseling sessions or other contacts with patients. Patients who remained infested after using either synergized pyrethrins or permethrin were encountered by 81.7% and 78.6% of pharmacists, respectively; these treatment failures occurred once or twice weekly in 58.1% of pharmacists' practices. Patients treating themselves more frequently or in higher doses with pesticides in an attempt to rid themselves of lice were reported by 62.6% of pharmacists. Patients reported the use of gasoline, kerosene, or other dangerous treatments once weekly or more in the experience of 42% of pharmacists. Resistant head lice had been a problem in their areas for 1 or 2 years for 42.8% of pharmacists. A smaller percentage (5.3%) of pharmacists had received official confirmation that resistant head lice were present in their areas. Pharmacists recommended nontoxic options (eg, combing and vacuuming) 19.8% of the time with positive results. Resistance seems to be a widespread, growing phenomenon and is not entirely related to patients' inability to use pesticides correctly. Pharmacists should consider recommending nontoxic alternatives that do not pose a threat to the patient or environment and do not contribute to resistance.

Treatment of Pediculosis Capitis

An endeavour to delineate the salient details of the treatment of head lice infestation has been made in the present article. Treatment modalities including over the counter permethrin and pyrethrin, and prescription medicines, including malathion, lindane, benzyl alcohol, spinosad are discussed. Salient features of alternative medicine and physical treatment modalities are outlined. The problem of resistance to treatment has also been taken cognizance of.

Treatment of pediculosis capitis: a critical appraisal of the current literature

Pediculosis capitis is the most common ectoparasitic disease in children in industrialized countries and extremely common in resource-poor communities of the developing world. The extensive use of pediculicides with a neurotoxic mode of action has led to the development and spread of resistant head lice populations all over the world. This triggered the development of compounds with other modes of action. The current literature on treatment approaches of head lice infestation was searched, and published randomized controlled trials were critically analyzed. The following compounds/family of compounds were identified: spinosad, a novel compound with a new neurotoxic mode of action, isopropyl myristate, 1,2-octanediol, ivermectin, plant-based products, and dimeticones. The efficacy and safety of these compounds are reviewed and recommendations for the treatment of pediculosis capitis in individuals as well as the interruption of ongoing epidemics are provided.

Survey assessment on pediatricians' attitudes on head lice management

Background

Pediculosis capitis is a worldwide health problem. One of the most important factor in effective head lice eradication is to ensure that infestation is adequately recognized and treated. Our survey investigated the knowledge and practice among primary care Italian pediatricians regarding to the prevention and treatment of head lice.

Methods

The questionnaire was distributed to all the pediatricians registered at the Annual Congress of Practice in Pediatrics held in Florence, Italy, November 11–12, 2011. It includes 10 questions in a multiple choice format, and one answer for each question was provided. The questionnaire was conceived by pediatricians at the Infectious Disease Unit of the Department of Science for the Health of Woman and Child, University of Florence. Questions were designed according to the guidelines by the Italian Pediatric Society (SIP), and international guidelines, such as the Centers for Disease Control and Prevention (CDC), and the American Academy of Pediatrics (AAP).

Results

Overall, 364/600 pediatricians (60.7% of physicians registered to the Congress) returned the questionnaire. The majority of them (232/364; 63,7%) believe that parents consult their primary care pediatrician only after the failure of other “remedies”. Mostly, they prescribe Malathion (116/364, 31,8%) as first line treatment. Two-hundred-fourty-three (66.7%) of participants consider creams, foams and gels the most effective formulations. Two-hundred-sixty-two of pediatricians interviewed (72.0%) suggest to repeat the treatment after one week, 37/364 (10.2%) after two weeks. The majority of the pediatricians interviewed reported that recurrences occur in less than 30% of cases (279/364; 76,6%). In their own opinion, most of recurrences are the consequence of a reinfestation in the community (259/264; 77%). Three-hundred-thirty-four (91.7%) of them have never prescribed oral therapy for the treatment of head lice. Finally, 289/364 (79.4%) pediatricians believe that no product is effective for prevention.

Conclusions

This is the first study that investigates the clinical practice of family pediatricians about the management and treatment of head lice globally, the Italian pediatricians surveyed proved to be quite informed on the head lice management. However, even in a country where pediatric assistance is free for everybody, a considerable proportion of parents do not seek advice to their own family pediatrician. Therefore, educations of parents, other than continuous updating of pediatricians, may contribute to a better management of head lice in the community.

Knowledge, attitudes, and practices of parents/guardians regarding pediculosis in the Umm el-Jimal district of Jordan

The aim of this study is to assess the prevalence of pediculosis capitis in one district in Jordan, and to determine the knowledge, attitudes and practices of parents/guardians regarding head lice. The study was performed in Jordan’s Umm el-Jimal district from February 2010 to May 2010, and involved the surveying of 105 randomly selected households containing a total of 213 children. The households’ parents were interviewed for their knowledge, attitudes and practices regarding pediculosis, and afterward their children’s hair was checked for head lice via a 5-min visual scalp examination. Chi-square testing was used to analyse the data, with statistical significance assumed at p < 0.05. The prevalence rate of pediculosis among the 213 children was found to be 14.6%. Parental knowledge of head lice was found to be very limited; only 35.2% of the parents/guardians correctly answered 10 of the 20 questions (50%), and only 17.1% correctly answered 14 questions (70%). More than 94% of the parents reported feeling shame upon learning that their children were infested with pediculosis, and nearly 90% felt too ashamed to ask for help from a healthcare provider. Many parents used traditional/local techniques that they believed to be effective in managing pediculosis; 61% of the parents applied kerosene to the scalps of infested individuals, 39.9% used medical shampoo and 37.6% used special combs. There is a clear deficiency in Jordanian parents’ knowledge of, and practices concerning, pediculosis capitis. It is recommended that the Jordanian Ministry of Health and local health departments work together to ensure the dissemination of accurate and consistent head lice information to families.

Pediculosis capitis: new insights into epidemiology, diagnosis and treatment

Pediculosis capitis is a ubiquitous parasitic skin disease caused by Pediculus humanus capitis. Head lice are highly specialised parasites which can propagate only on human scalp and hair. Transmission occurs by direct head-to-head contact. Head lice are vectors of important bacterial pathogens. Pediculosis capitis usually occurs in small epidemics in play groups, kindergartens and schools. Population-based studies in European countries show highly diverging prevalences, ranging from 1% to 20%. The diagnosis of head lice infestation is made through the visual inspection of hair and scalp or dry/wet combing. The optimal method for the diagnosis of active head lice infestation is dry/wet combing. Topical application of a pediculicide is the most common treatment. Compounds with a neurotoxic mode of action are widely used but are becoming less effective due to resistant parasite populations. Besides, their use is restricted by safety concerns. Dimeticones, silicone oils with a low surface tension and the propensity to perfectly coat surfaces, have a purely physical mode of action. This group of compounds is highly effective and safe, and there is no risk that head lice become resistant. The control of epidemics requires active contact tracing and synchronised treatment with an effective and safe pediculicide.

Epidemiological aspects of Pediculosis capitis and treatment evaluation in primary-school children in Iran

This study was undertaken to assess the prevalence of and epidemiological factors associated with, head lice infections in Iranian primary schools in 2006 and evaluate data on the therapeutic efficacy of lindane shampoo. A total of 40586 children (19774 boys (48.72%) and 20812 girls (51.28%)] from 198 Governmentprimary schools in Kerman, were screened for head lice between March and June 2006. The diagnosis of head lice infestation was confirmed by clinical inspection of scalp and hair for the presence of adult lice nymphal stage, or eggs (nit) by line-toothed head lice comb. All children infested with lice were treated with lindane shampoo (1% gamma benzene hexachloride). The overall prevalence of head lice infestation was 1.8%. The prevalence of infestation was significantly higher in girls (2.9%) than in boys (0.6%) (p = 0.000). The infestation rate was greater among pupils who were living in rural areas (4.6%) than in urban areas (1.5%). Of the 721 children with a positive examination result, 424 pupils (58.8%) were reported as having been infested with head lice in the previous 6 months. Mother's education level was a significant risk factor in this model (p < 0.05). At 2 weeks after the primary treatment, the success rates of treatment were 49%. Comprehensive survey in our work showed the better future of the disease and related factors. Education campaigns by health care officials, physicians and teachers are expected to be helpful for head lice control. It is essential that governments should be supported form cooperation between the school authorities and public health centers to successful control head lice infestation in primary school. Also there is an urgent need to identify safe, novel insecticides for proved efficacy.

In vitro efficacy of over-the-counter botanical pediculicides against the head louse Pediculus humanus var capitis based on a stringent standard for mortality assessment

Infestation of the head louse Pediculus humanus var capitis DeGeer (Phthiraptera: Pediculidae) is an important public health problem in Australia, with up to a third of children infested in some primary schools. Insecticide resistance and inadequate attention to the application instructions of topical pediculicides are common reasons for treatment failure. This study evaluated six popular Australian over-the-counter products against head lice, primarily comprised of different botanical extracts, and compared them with permethrin 1% (Quellada) and a non-treatment control in order to assess their in vitro efficacy. We also assessed commonly used criteria for evaluating pediculicide efficacy in vitro. All tested products failed to demonstrate high levels of efficacy with the exception of Tea Tree Gel((R)), which outperformed 1% permethrin. Permethrin had a high level of efficacy, but using stringent criteria 18% of lice were not dead at 3 h, indicating some resistance to Quellada. Commonly used less stringent criteria were shown to overestimate mortality of head lice as a result of the protective phenomenon of stasis or sham death observed in exposed lice that may recover after some time. Using two different levels of stringency resulted in different rankings of efficacy for most products, with the exception of the first ranked product, Tea Tree Gel. Rankings of efficacy also varied over time, even within the different assessment criteria. Government regulatory agencies should require standard in vitro tests using stringent mortality criteria, with an observation period of >or= 6 h, to determine the efficacy of new pediculicides, and only products that cause a minimum mortality rate (e.g. 80%) in head lice collected from the target population should be licensed for sale.

Efficacy of neem seed extract shampoo on head lice of naturally infected humans in Egypt

Sixty heavily lice-infested male and female children (4-15 years) were selected and subjected to the treatment with a neem seed extract shampoo. Twenty to thirty milliliter of the shampoo were thoroughly mixed with completely wet hair and rubbed in to reach the skin of the scalp. After 5, 10, 15 and 30 min, the shampoo was washed out and the hair basically combed. Head lice were collected and examined. The neem seed extract shampoo proved to be highly effective against all stages of head lice. No obvious differences regarding the efficacy of the shampoo were observed between an exposure time of 10, 15 or 30 min. No side effects, such as skin irritation, burning sensations, or red spots on the scalp, forehead or neck, respectively, were observed.

Albendazole: single or combination therapy with permethrin against pediculosis capitis

Pediculosis capitis is a worldwide problem and a growing concern because of resistance to pediculicides. In the present study, we investigated whether albendazole could be used in the treatment of pediculosis capitis in combination with 1% permethrin or alone. A total of 150 children were randomly divided to five groups of 30 each. Group 1 got albendazole in a single dose (400 mg), group 2 got albendazole at 400 mg for 3 days, group 3 was given 1% permethrin, group 4 took 1% permethrin and albendazole in a single dose (400 mg), and group 5 got 1% permethrin and albendazole in a dose of 400 mg for 3 days. Groups given albendazole were also given another 400 mg dose of albendazole after 1 week. The success rate of treatment at the 2-week follow-up for all groups was 61.5%, 66.6%, 80.0%, 84.6%, and 82.1%, respectively. No statistically significant difference was found between the groups. The results of this study suggest that albendazole is effective against pediculosis capitis and there is no synergistic effect between albendazole and 1% permethrin.

Evaluation of extracts and oils of tick-repellent plants from Sweden

Abstract. Leaves of Myrica gale Linnaeus (Myricaceae), Rhododendron tomentosum (Stokes) H. Harmaja (formerly Ledum palustre Linnaeus: Ericaceae) and Artemisia absinthium Linnaeus (Asteraceae) were extracted with organic solvents of different polarities and the essential oils of leaves were obtained by steam distillation. The extracts or oils were tested in the laboratory for repellency against host-seeking nymphs of Ixodes ricinus Linnaeus (Acari: Ixodidae). Rhododendron tomentosum oil, 10%, diluted in acetone, exhibited 95% repellency; R. tomentosum and A. absinthium extracts in ethyl acetate, > 70% repellency; A. absinthium extract in hexane, approximately 62% repellency; and M. gale oil, 10%, approximately 50% repellency on I. ricinus nymphs. Compounds in the leaf extracts or in the oils were collected by solid phase microextraction (SPME) and identified by gas chromatography-mass spectrometry (GC-MS) and/or MS. Characteristic volatiles detected from oil or extract of M. gale were the monoterpenes 1,8-cineole, alpha-terpineol, 4-terpineol and thujenol; and of R. tomentosum myrcene and palustrol. Characteristic volatiles from leaf extracts of A. absinthium were sabinene, oxygenated monoterpenes, e.g. thujenol and linalool, and geranyl acetate. Each plant species synthesized numerous volatiles known to exhibit acaricidal, insecticidal, 'pesticidal' and/or arthropod repellent properties. These plants may be useful sources of chemicals for the control of arthropods of medical, veterinary or agricultural importance.

Scabies: New Future for a Neglected Disease

Scabies is a disease of global proportions in both human and animal populations, resulting from infestation of the skin with the "itch" mite Sarcoptes scabiei. Despite the availability of effective chemotherapy the intensely itching lesions engender significant morbidity primarily due to secondary sepsis and post-infective complications. Some patients experience an extreme form of the disease, crusted scabies, in which many hundreds of mites may infest the skin causin severe crusting and hyperkeratosis. Overcrowded living conditions and poverty have been identified as significant confounding factors in transmission of the mite in humans. Control is hindered by difficulties with diagnosis, the cost of treatment, evidence for emerging resistance and lack of effective vaccines. Historically research on scabies has been extremely limited because of the difficulty in obtaining sufficient quantities of the organism. Recent molecular approaches have enabled considerable advances in the study of population genetics and transmission dynamics of S. scabiei. However, the most exciting and promising development is the potential exploitation of newly available data from S. scabiei cDNA libraries and EST projects. Ultimately this knowledge may aid early identification of disease, novel forms of chemotherapy, vaccine development and new treatment possibilities for this important but neglected parasite.

A survey on head lice infestation in Korea (2001) and the therapeutic efficacy of oral trimethoprim/sulfamethoxazole adding to lindane shampoo

Total of 7,495 children including 3,908 boys and 3,587 girls from a kindergarten and 15 primary schools were examined for head lice infestation (HLI). The overall prevalence of HLI in this study was found to be 5.8%. Head lice were much more commonly detected in girls than in boys with prevalence of 11.2% and 0.9%, respectively. Sixty-nine children with HLI were treated with 1% lindane shampoo alone (group 1), and 45 children with HLI were treated with 1% lindane shampoo and oral trimethoprim/sulfamethoxazole (group 2), and follow-up visits were conducted 2 and 4 weeks later. The children who still had HLI 2 weeks after the primary treatment were treated again. At the 2-week follow-up visit, the treatment success rates of groups 1 and 2 were 76.8% and 86.7%, respectively, and at the 4-week follow-up visit, the rates were 91.3% and 97.8%, respectively. No statistically significant synergistic effect was observed for the combination of a 1% lindane shampoo and oral trimethoprim/sulfamethoxazole.

Getting ahead of head lice

Dermatologists are the nominal experts in the management of head lice in Australia, yet many dermatologists infrequently treat patients with this condition. Most people are managed in the community by school nurses, local council health officers, pharmacists, paediatricians or general practitioners. Only a small number will present to the dermatologist and commonly these patients will have tried a variety of treatments and failed to respond. Resistance is reported to all of the currently available insecticide treatments and this makes management of this common community-acquired infestation more involved.