Molecular analysis of mitochrondrial cytb of Pediculus humanus capitis in Thailand revealed potential historical connection with South Asia.

BACKGROUND: Pediculus humanus capitis or head louse is an obligate ectoparasite and its infestation remains a major public health issue worldwide. Molecular analysis divides head lice into six clades and intra-clade genetic differences have been identified. Several hypotheses have been formulated to elucidate the discrepancies of the variety of head lice among different regions of the world. It is currently concluded that head lice distribution might be associated with human migration history. This study aims to investigate genetic data of human head lice in Thailand. We believe that the analysis could help establish the correlation between local and global head lice populations. METHOD: We investigated mitochondrial cytochrome b (cytb) gene of the collected 214 head lice to evaluate genetic diversity from 15 provinces among 6 regions of Thailand. The head lice genes were added to the global pool for the phylogenetic tree, Bayesian tree, Skyline plot, and median joining network construction. The biodiversity, neutrality tests, and population genetic differentiation among the 6 Thailand geographic regions were analyzed by DNAsp version 6. RESULTS: The phylogenetic tree analysis of 214 collected head lice are of clade A and clade C accounting for roughly 65% and 35% respectively. The Bayesian tree revealed a correlation of clade diversification and ancient human dispersal timeline. In Thailand, clade A is widespread in the country. Clade C is confined to only the Central, Southern, and Northeastern regions. We identified 50 novel haplotypes. Statistical analysis showed congruent results between genetic differentiation and population migration especially with South Asia. CONCLUSIONS: Pediculosis remains problematic among children in the rural areas in Thailand. Cytb gene analysis of human head lice illustrated clade distribution and intra-clade diversity of different areas. Our study reported novel haplotypes of head lice in Thailand. Moreover, the statistic calculation provided a better understanding of their relationship with human, as an obligate human parasite and might help provide a better insight into the history of human population migration. Determination of the correlation between phylogenetic data and pediculicide resistance gene as well as residing bacteria are of interest for future studies.

Stigma resulting from head lice infestation: A concept analysis and implications for public health.

AIM: The aim of this concept analysis was to examine stigma in the context of head lice, illuminating its components and providing insights for the development of appropriate nursing interventions. BACKGROUND: Stigma associated with the phenomenon of head lice management is pervasive, promulgating fear and influencing policy and treatment practices. Few studies have examined stigma in this context. METHOD: The method followed was the Rodgers's evolutionary method. DATA SOURCES: Health, education, and social sciences databases were searched and yielded 20 articles spanning 1996-2018 used to create a relevant literature review. RESULTS: Stigma arising from head lice infestation is preceded by an actual or perceived case of head lice, negative perceptions of lice, negative perception of groups or persons with head lice, or being associated with a group or person of lesser status believed to be a carrier of head lice. Defining attributes include marks of infestation, negative and unfair beliefs, and shame. Consequences of stigma are economic costs, social costs, mistreatment, and overtreatment with pediculicides. CONCLUSION: The concept of stigma in the context of head lice management is multifaceted. Further research is required to understand the magnitude of stigma as well as other factors associated with optimal treatment of children with head lice.

Serie parasitosis en dermatología: pediculosis / Parasitosis in dermatology: pediculosis

La enfermedad producida por Pediculus humanus capitis, conocida como pediculosis, es una parasitosis específica del ser humano de distribución mundial. El contagio puede ser directo por contacto con el cuero cabelludo de una persona afectada, o por fómites contaminados con parásitos, por lo que no distingue raza, sexo, edad ni nivel socioeconómico. Presentamos el caso de una paciente de 80 años con una forma típica de pediculosis. (AU)

The disease caused by Pediculus humanus capitis, known as pediculosis, is a human specific parasitosis. It has a worldwide distribution. Transmission can be by direct contact with the scalp of an affected person or by contaminated fomites with parasites. This infestation makes no distinction of race, sex, age, or socioeconomic status. We present a case of an 80 years old patient with a typical case of pediculosis. (AU)

Effect of permethrin-impregnated underwear on body lice in sheltered homeless persons: a randomized controlled trial.

IMPORTANCE: The control of body lice in homeless persons remains a challenge. OBJECTIVE: To determine whether the use of long-lasting insecticide-treated underwear provides effective long-term protection against body lice in homeless persons. DESIGN, SETTING, AND PARTICIPANTS: A randomized, double-blind, placebo-controlled trial was conducted in February and December 2011 in 2 homeless shelters (Madrague Ville and Forbin) in Marseille, France. Of the 125 homeless persons screened for eligibility, 73 body lice-infested homeless persons, 18 years or older, were enrolled. INTERVENTIONS: Body lice-infested homeless persons were randomly assigned to receive 0.4% permethrin-impregnated underwear or an identical-appearing placebo for 45 days, in a 1:1 ratio, with a permuted block size of 10. Visits were scheduled at days 14 and 45. Data regarding the presence or absence of live body lice were collected. MAIN OUTCOMES AND MEASURES: The primary and secondary end points were the proportions of homeless persons free of body lice on days 14 and 45, respectively. Mutations associated with permethrin resistance in the body lice were also identified. RESULTS: Significantly more homeless persons receiving permethrin-impregnated underwear than homeless persons receiving the placebo were free of body lice on day 14 in the intent-to-treat population (28% vs 9%; P = .04), with a between-group difference of 18.4 percentage points (95% CI, 1.4-35.4), and in the per-protocol population (34% vs 11%; P = .03), with a between-group difference of 23.7 percentage points (95% CI, 3.6-43.7). This difference was not sustained on day 45. At baseline, the prevalence of the permethrin-resistant haplotype was 51% in the permethrin group and 44% in the placebo group. On day 45, the permethrin-resistant haplotype was significantly more frequent in the permethrin group than in the placebo group (73% vs 45%, P < .001). CONCLUSION AND RELEVANCE: Permethrin-impregnated underwear is more efficient than placebo at eliminating body louse infestations by day 14; however, this difference was not sustained on day 45. The use of permethrin may have increased the resistance to permethrin in body lice and thus must be avoided. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01287663.

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.

Assessment of the safety and efficacy of three concentrations of topical ivermectin lotion as a treatment for head lice infestation.

BACKGROUND: Ivermectin is a broad-spectrum parasiticide in widespread systemic use, including as an off-label treatment for head lice infestation. The potential of the topical use of ivermectin as a treatment for head lice infestation was suggested by an in vitro report of a novel lotion formulation. OBJECTIVES: This study investigated the relative effectiveness of three ivermectin lotion concentrations (0.15, 0.25, and 0.5%) compared with vehicle placebo in eliminating head lice infestation. METHODS: In this randomized, blinded study, 78 head lice-infested subjects, aged 2-62 years, received a single, 10-minute application of product on day 1. Evaluations were completed at two and six hours post-application, and on days 2, 8 (±1), and 15 (+2). Safety was assessed according to the evaluations of trained observers and adverse event (AE) reports. Efficacy was assessed according to scalp and hair examinations. RESULTS: Compared with placebo, all ivermectin concentrations resulted in the statistically significant (P ≤ 0.003) eradication of head lice through to day 15, with the highest level of eradication (73.7%) in subjects who received the 0.5% concentration. The severity of pruritus decreased from baseline in all treatment groups, including the placebo group, from six hours post-treatment to day 15, with the greatest reduction in the 0.5% concentration group. No ocular irritation was observed. All three ivermectin treatment strengths and vehicle were well tolerated. CONCLUSIONS: A single application of a 0.5% concentration of this ivermectin lotion formulation shows promise as a safe and effective treatment for head lice infestation and the associated signs of pruritus.

Prevalence and risk factors of Pediculus (humanus) capitis (Anoplura: Pediculidae), in primary schools in Sanandaj City, Kurdistan Province, Iran.

Human head lice, Pediculus (humanus) capitis, infest people worldwide and are most prevalent in children. The aim of this study was to determine the prevalence of head lice, in relation to socioeconomic status of the family and hygienic practices in the home. The prevalence rate was determined in 27 primary schools that had 810 students in Sanandaj city who were selected by multistage, systematic random sampling. A total of 38 students from all grades were infested with different rates of infestations. In addition, standard questionnaire recorded information about demographic features of each student were fulfilled. Children aged 10-11 years were the most frequently affected, there was a significant relationship between head louse infestation, family income and parents education level (α=5%). Pediculosis is a public health problem in many parts of the world. Pediculosis was found to be more prevalent among children of fathers with lower level of education and socioeconomic status, it is necessary to give health education to families in order to prevent pediculosis in this area.

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.

Of lice and math: using models to understand and control populations of head lice.

In this paper we use detailed data about the biology of the head louse (pediculus humanus capitis) to build a model of the evolution of head lice colonies. Using theory and computer simulations, we show that the model can be used to assess the impact of the various strategies usually applied to eradicate head lice, both conscious (treatments) and unconscious (grooming). In the case of treatments, we study the difference in performance that arises when they are applied in systematic and non-systematic ways. Using some reasonable simplifying assumptions (as random mixing of human groups and the same mobility for all life stages of head lice other than eggs) we model the contagion of pediculosis using only one additional parameter. It is shown that this parameter can be tuned to obtain collective infestations whose characteristics are compatible with what is given in the literature on real infestations. We analyze two scenarios: One where group members begin treatment when a similar number of lice are present in each head, and another where there is one individual who starts treatment with a much larger threshold ("superspreader"). For both cases we assess the impact of several collective strategies of treatment.

[Ectoparasites. Part 2: Bed bugs, Demodex, sand fleas and cutaneous larva migrans]. / Ektoparasitosen. Teil 2: Bettwanzen, Haarbalgmilben, Sandfloh und Larva migrans cutanea.

Ectoparasites or epidermal parasites include a very heterogenous group of infections of the outer layers of the skin. Worldwide the most common are scabies, lice, tungiasis, and hookworm-induced cutaneous larva migrans. In recent years, bed bug infestations in hotels or vacation homes seem to have become more frequent. Demodex folliculorum and Demodex brevis are found in the facial and scalp hair follicles in 95% of individuals. Classic Demodex folliculitis is often overlooked in differential diagnostic considerations. This inflammatory sebaceous gland disease as well as Demodex blepharitis both provide a diagnostic and therapeutic challenge. Permethrin can be used topically against demodicosis. Vacationers who go barefoot on beaches in tropical Africa, South America and subtropical Asia risk infestations from female sand fleas. The lesions can be curetted or removed with a punch biopsy, then treated with antiseptics or even systemic antibiotics if a secondary infection develops. Cutaneous larva migrans is one of the most common imported ectoparasite infections from the tropics. Topical treatment measures include thiabendazole or cryotherapy. If the infestation is severe, systemic antihelminthics or ivermectin can be employed.

[Ectoparasites. Part 1: lice and fleas]. / Ektoparasitosen. Teil 1: Läuse und Flöhe.

Ectoparasites and epidermal parasitic skin diseases are a heterogeneous group of infections of the external layer of the skin. The most common forms world-wide are scabies, lice (Pediculosis capitis, corporis, vestimentorum and pubis), tungiasis and the hookworm-associated Larva migrans cutanea. The head louse is the most widespread parasite in children in Germany. The symptoms, apart from pruritus, eczematous skin eruptions and ictus reactions of the skin, are often unspecific and many differential diagnoses must be considered. Treatment of ectoparasites includes manual procedures, such as repeated cleansing and combing out of lice-infected hair and also local antiparasitic treatment with permethrin, pyrethrum extract, allethrin and dimeticon. Lindan which has been used for decades can no longer be used in medications after 2008 after a decision of the EU Commission. Failure of treatment of head lice can be a result of errors in the treatment which favor survival of the eggs, larvae or adults. This can be a result of too short reaction times and too economical use or unequal distribution of medications, excessive dilution due to wet hair or omitting repeated treatment stages. Additionally resistance of head lice to pyrethrum is a known phenomenon and has been reported in several countries.

A stochastic model for head lice infections.

We investigate the dynamics of head lice infections in schools, by considering a model for endemic infection based on a stochastic SIS (susceptible-infected-susceptible) epidemic model, with the addition of an external source of infection. We deduce a range of properties of our model, including the length of a single outbreak of infection. We use the stationary distribution of the number of infected individuals, in conjunction with data from a recent study carried out in Welsh schools on the prevalence of head lice infections, and employ maximum likelihood methods to obtain estimates of the model parameters. A complication is that, for each school, only a sample of the pupils was checked for infection. Our likelihood function takes account of the missing data by incorporating a hypergeometric sampling element. We arrive at estimates of the ratios of the "within school" and "external source" transmission rates to the recovery rate and use these to obtain estimates for various quantities of interest.

Host-symbiont interactions of the primary endosymbiont of human head and body lice.

The first mycetome was discovered more than 340 yr ago in the human louse. Despite the remarkable biology and medical and social importance of human lice, its primary endosymbiont has eluded identification and characterization. Here, we report the host-symbiont interaction of the mycetomic bacterium of the head louse Pediculus humanus capitis and the body louse P. h. humanus. The endosymbiont represents a new bacterial lineage in the gamma-Proteobacteria. Its closest sequenced relative is Arsenophonus nasoniae, from which it differs by more than 10%. A. nasoniae is a male-killing endosymbiont of jewel wasps. Using microdissection and multiphoton confocal microscopy, we show the remarkable interaction of this bacterium with its host. This endosymbiont is unique because it occupies sequentially four different mycetomes during the development of its host, undergoes three cycles of proliferation, changes in length from 2-4 microm to more than 100 microm, and has two extracellular migrations, during one of which the endosymbionts have to outrun its host's immune cells. The host and its symbiont have evolved one of the most complex interactions: two provisional or transitory mycetomes, a main mycetome and a paired filial mycetome. Despite the close relatedness of body and head lice, differences are present in the mycetomic provisioning and the immunological response.

Safety and efficacy of pediculicides for head lice.

Head lice infestation is a common and growing problem, primarily affecting school-aged children. There are growing numbers of treatment failures due to the emergence of treatment-resistant lice to the popular over-the-counter products that have been used for the past several decades. Resistance has also decreased the efficacy of lindane, a prescription pediculicide that has been commonly used for several generations. Malathion, recently reintroduced in the US as a prescription pediculicide, has been associated with some treatment resistance depending upon its formulation. Other insecticidal treatments, such as ivermectin, will have to be developed further, given the limited options presently available for the treatment of head lice. Given the number of anecdotal and market-driven reported studies on head lice, assessment of topical lice therapies requires standardised in vitro testing. Based on concerns about safety and decreasing efficacy due to resistance, a reassessment of the general topic of pediculicides for head lice is warranted.

Overview: the state of head lice management and control.

Head lice infestations affect millions of people in the United States. Children become infested more often than adults and account for the largest percentage of infestations. Head lice have not been shown to transfer disease, and they are not associated with serious morbidity. The most common effect of lice infestation is pruritus of the scalp with occasional cutaneous infection caused by scratching. Nevertheless, many schools have "no-nit" policies, which require the dismissal of children from school if nits or lice are found. These policies are ineffective in preventing infestations and result in many missed days of school. Lice infestations are most effectively managed with pediculicides. Pyrethroids are the mainstay of over-the-counter products. Prescription pediculicides include OVIDE (malathion) Lotion, 0.5% and lindane (formerly marketed as Kwell). Resistance to pyrethroids due to misuse and overuse has been documented. Lindane resistance also has been reported, and serious safety issues about lindane have been raised by the Food and Drug Administration. Lindane labeling now includes warnings and several restrictions in its use. Malathion is not associated with major systemic safety issues or the development of resistance within the United States. A contributor to pediculicide resistance is misdiagnosis of lice infestations. Survey data reveal frequent misdiagnosis of infestations in children who do not have live lice. Physicians generally are more likely to misdiagnose infestations than nonhealthcare providers. Misdiagnosis contributes to resistance by causing overuse, and consequently overexposure, of pediculicides. These agents should be used only if live lice or viable nits are discovered. Head lice infestations generally do not contribute to health risks for individuals or the public. The most serious consequence is the social cost of missed school days and the associated cost of lost productivity and wages of parents who must care for children sent home from school. Better diagnosis, more appropriate use of pediculicides, and elimination of no-nit policies will improve the overall management of head lice infestations.