Scabies and pediculosis

Protocol for the systematic review of the prevention, treatment and public health management of impetigo, scabies and fungal skin infections in resource-limited settings

BACKGROUND

Impetigo, scabies, and fungal skin infections disproportionately affect populations in resource-limited settings. Evidence for standard treatment of skin infections predominantly stem from hospital-based studies in high-income countries. The evidence for treatment in resource-limited settings is less clear, as studies in these populations may lack randomisation and control groups for cultural, ethical or economic reasons. Likewise, a synthesis of the evidence for public health control within endemic populations is also lacking. We propose a systematic review of the evidence for the prevention, treatment and public health management of skin infections in resource-limited settings, to inform the development of guidelines for the standardised and streamlined clinical and public health management of skin infections in endemic populations.

METHODS

The protocol has been designed in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols statement. All trial designs and analytical observational study designs will be eligible for inclusion. A systematic search of the peer-reviewed literature will include PubMed, Excertpa Medica and Global Health. Grey literature databases will also be systematically searched, and clinical trials registries scanned for future relevant studies. The primary outcome of interest will be the clinical cure or decrease in prevalence of impetigo, scabies, crusted scabies, tinea capitis, tinea corporis or tinea unguium. Two independent reviewers will perform eligibility assessment and data extraction using standardised electronic forms. Risk of bias assessment will be undertaken by two independent reviewers according to the Cochrane Risk of Bias tool. Data will be tabulated and narratively synthesised. We expect there will be insufficient data to conduct meta-analysis. The final body of evidence will be reported against the Grades of Recommendation, Assessment, Development and Evaluation grading system.

DISCUSSION

The evidence derived from the systematic review will be used to inform the development of guidelines for the management of skin infections in resource-limited settings. The evidence derived will be intended for use by clinicians, public health practitioners and policy makers in the treatment of skin infections and the development of skin infection control programmes. The review will identify any gaps in the current evidence to provide direction for future research.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42015029453.

Bullous Scabies

Scabies is a common contagious cutaneous disease and usually affects the young, characterized by polymorphous lesions that may present as burrows, pruritic papules, and inflammatory nodules. Bullous scabies (BS) is its rather rare subtype, mimicking bullous pemphigoid. We report a 15-year-old Chinese boy presenting with 1-month history of pruritic bullae on his penile skin, showing poor response to both topical steroids and systemic antihistamines, but cured by sulfur ointment alone. No recurrence occurred in the 5 years of follow-up. We also reviewed the published cases. Up to date, 44 cases, including the present, have been reported. Of them, 30 were male and 14 were female. The age range was from 1 to 89 years old, with a median age of 70.6 years. The bullous lesions may involve the arms, legs, trunk, genitals, feet, buttocks, thighs, neck, inguinal folds, and may even be generalized. Trunk and extremities are the most common involved locations. Facial or mucosa involvement had never been reported. The histological findings present as a subepidermal split with variable inflammatory infiltrate predominantly neutrophils, and eosinophilic spongiosis, or both. Eighteen of 32 patients showed positive deposition of linear-granular IgG or complement 3 alone or in various combinations, and five of 24 patients revealed circulating IgG. All the 40 cases with therapeutic details were cured by antiscabietic remedy. BS always involves the trunk and extremities. It has a predilection for elderlies and males. The treatments for BS are similar to those of classical scabies.

Management and Treatment of Human Lice

Of the three lice (head, body, and pubic louse) that infest humans, the body louse is the species involved in epidemics of louse-borne typhus, trench fever, and relapsing fever, but all the three cause pediculosis. Their infestations occur today in many countries despite great efforts to maintain high standards of public health. In this review, literature searches were performed through PubMed, Medline, Google Scholar, and EBSCOhost, with key search words of "Pediculus humanus", "lice infestation", "pediculosis", and "treatment"; and controlled clinical trials were viewed with great interest. Removing lice by hand or with a lice comb, heating infested clothing, and shaving the scalp were some of the oldest methods of controlling human lice. Despite the introduction of other resources including cresol, naphthalene, sulfur, mercury, vinegar, petroleum, and insecticides, the numbers of lice infestation cases and resistance have increased. To date, viable alternative treatments to replace insecticides have been developed experimentally in vitro. Today, the development of new treatment strategies such as symbiotic treatment and synergistic treatment (antibiotics + ivermectin) in vitro has proved effective and is promising. Here, we present an overview on managing and treating human lice and highlight new strategies to more effectively fight pediculosis and prevent resistance.

[Main parasitic skin disorders]

Cutaneous parasitic skin diseases are frequent in human pathology. There are few reliable epidemiological data on the prevalence and/or incidence of such diseases. Skin parasites are cosmopolitan but their global distribution is heterogenous; prevalence is especially high in subtropical and tropical countries. They are mainly due to arthropods (insects and mites). Many species of parasites are involved, explaining the diversity of their clinical signs. The most common are caused by ectoparasites such as scabies or pediculosis (head lice, body lice and pubic lice). Clinical signs may be related to the penetration of the parasite under the skin, its development, the inoculation of venom or allergic symptoms. Diagnosis can be easy when clinical signs are pathognomonic (e.g. burrows in the interdigital web spaces in scabies) or sometimes more difficult. Some epidemiological characteristics (diurnal or nocturnal bite, seasonality) and specific clinical presentation (single or multiple bites, linear or grouped lesions) can be a great diagnostic help. Modern non-invasive tools (dermoscopy or confocal microscopy) will play an important role in the future but the eye and experience of the specialist (dermatologist, parasitologist, infectious disease specialist or entomologist) remains for the time the best way to guide or establish a diagnosis. For most skin parasites, therapeutic proposals are rarely based on studies of high level of evidence or randomized trials but more on expert recommendations or personal experience.

Scabies: Advances in Noninvasive Diagnosis

Scabies is a common, highly contagious skin parasitosis caused by Sarcoptes scabiei var. hominis. Early identification and prompt treatment of infested subjects is essential, as missed diagnosis may result in outbreaks, considerable morbidity, and significantly increased economic burden. The standard diagnostic technique consists of mites' identification by microscopic examination of scales obtained by skin scraping. This is a time-consuming and risk-associated procedure that is also not suitable to a busy practice. In recent years, some advanced and noninvasive techniques such as videodermatoscopy, dermatoscopy, reflectance confocal microscopy, and optical coherence tomography have demonstrated improved efficacy in the diagnosis of scabies. Their advantages include rapid, noninvasive mass screening and post-therapeutic follow-up, with no physical risk. A greater knowledge of these techniques among general practitioners and other specialists involved in the intake care of overcrowded populations vulnerable to scabies infestations is now viewed as urgent and important in the management of outbreaks, as well as in consideration of the recent growing inflow of migrants in Europe from North Africa.

[Randomised clinical trial to evaluate the efficacy and safety of a new pediculicide made with saponified olive oil in the eradication of Pediculus humanus capitis]

INTRODUCTION

The aim of the study was to evaluate the efficacy and safety of a new pediculicide in the eradication of Pediculus humanus capitis infestation.

MATERIAL AND METHODS

A randomised clinical trial was designed, in which children aged between 5 and 15 years diagnosed with pediculosis were selected. Treatment was administered on days 1 and 7 after selection, and they were evaluated in 4 visits (day 2, 7, 9, and 14). The product under evaluation with saponified olive oil was Inex Pediculicide Soap^®, which was compared with Paranix^®, with a similar mechanism of action. The primary efficacy endpoint was the eradication of the parasite by day 14 (louse-free rate), using an intention to treat analysis.

RESULTS

Six paediatricians from 5 Primary Health Care centres in the Community of Madrid (Spain) and one private clinic participated in the study. A total of 45 children were included, of which 75.6% were girls (n=34). The mean age was 7.1 years (95% CI 6.3-7.9). The large majority (80%) were middle class, and 82.2% had a history of previous pediculosis. The efficacy at 14 days was 76.2% (95% CI 52.8-91.8) in the group treated with Inex Pediculicide Soap^® group, and 79.2% (95% CI 57.9-92.9) in Paranix^® group (NNT=33.3). No adverse effects were observed with treatment.

CONCLUSIONS

The 2 products were effective and safe in the eradication therapy Pediculus humanus capitis, with no statistical differences.

Efficacy assessment of biocides or repellents for the control of Sarcoptes scabiei in the environment

BACKGROUND

Sarcoptes scabiei infection is a contagious disease affecting both humans and animals. The transmission occurs either by direct contact or from the environment where mites could survive several days remaining infective. The number of products available for environmental control of S. scabiei is very limited. The objective of the present study was to assess the efficacy of biocides or repellents against S. scabiei var suis.

METHODS

Tested products included pyrethroids: permethrin, esdepallethrin and bioresmethrin, bifenthrin, cypermethrin and imiprothrin, cyfluthrin, tetramethrin and sumithrin. We also tested repellents: DEET, icaridin and IR3535. Sarcoptes scabiei var suis mites were collected from experimentally-infected pigs. For each test, 20 live mites of all motile stages were placed in a plastic Petri dish and sprayed uniformly by each product. Control mites were sprayed by distilled water. The study was performed in triplicate under room conditions and the mites were inspected under a stereomicroscope at intervals (5, 10, 15, 20, 25, 30, 40, 50, 60 min, 2, 3, 4, 5 and 24 h) after exposure to the products.

RESULTS

All the products, except the combination of tetramethrin and sumithrin (A-PAR), were able to kill all mites within 24 h. The median survival time was 50 ± 30.4 min, 120 ± 309 min, 10 ± 5.9 min, 40 ± 36.8 min, 15 ± 7.3 min, 180 ± 417 min and 1440 ± 600 min when mites were exposed to permethrin 4 %, permethrin 0.6%, esdepallethrin and bioresmethrin, bifenthrin, cypermethrin and imiprothrin, cyfluthrin, tetramethrin and sumithrin, respectively. The median survival time was 20 ± 6.5 min, 15 ± 4.3 min, 30 ± 42.1 min and 15 ± 4.9 min for DEET 25, DEET 50, icaridin 20 and IR3535 20%, respectively.

CONCLUSIONS

The results of the present study could support evidence-based use of biocides and repellents in households, hospitals and farms.

Treatment of human head lice infestations in a single application with a new galenic lotion

To evaluate the efficiency and safety of a new galenic meta-emulsion for the treatment of human head lice (Pediculus capitis) in a single application. A controlled clinical study was conducted comparing lice infestation and nit hatching observed before and after a treatment in a single application. Eighty-two of the 87 children included completed the study. An infestation control was performed on 36 and 46 children, 8 and 24 h respectively after application. Five days later, a meticulous hair examination was carried out to check that the lice infestation was completely cured. After a single application of the lotion being tested, an examination of the scalp with a head lice detection comb, as well as an examination of the rinsing water and the towel used for drying after washing, showed that out of the total 1285 lice, there were no live lice. The percentage of nits hatching before treatment was close to 70%. In comparison, after an 8-h treatment (t(+8)), the percentage of nits hatching was 2.1%, with only 0.35% of living nymphs. After a 24-h treatment (t(+24)), 1.9% hatched with 0.38% living nymphs. Nymphs were revealed to be non-viable. After 5 days (t(+120)), no living adult or immature lice were found on the subjects tested. Moreover, observation of tolerance levels to this treatment at days 1, 5 and 12 showed no side effects. The specific galenic lotion completely cured head lice infestation in the population studied in a single application. The lotion, a patented meta-emulsion, has a mechanical action that asphyxiates lice and nits. Considering the advantages of the single application, the possibility of complete concomitant therapeutics for a whole school population within only 1 day and the high level of tolerance to this treatment, this approach seems simple and promising.

[Penile dermatoses]

The diagnostics of penile skin alterations represent a urological and dermatological challenge. The spectrum of differential diagnoses ranges from benign skin alterations with no clinical significance, through infections, vesiculobullous diseases and neoplasms up to acute diseases necessitating emergency interventions. Evidence-based therapy concepts are not available for all these diseases and due to the rarity an interdisciplinary cooperation is expedient and promising.

Ectoparasites of medical and veterinary importance: drug resistance and the need for alternative control methods

OBJECTIVES

Despite multiple attempts at eradication, many ectoparasites of humans and domestic livestock remain a persistent problem in the modern world. For many years, a range of pesticide drugs including organophosphates, organochlorides and synthetic pyrethroids provided effective control of these parasites; but intensive use of these drugs has led to the evolution of resistance in many target species. This paper aims to review the effectiveness of current control methods and discuss potential alternatives for the long term sustainable control of ectoparasites.

KEY FINDINGS

Important medical ectoparasites such as scabies mites, head lice and bed bugs present a significant public health problem, and so adequate control methods are essential. Ectoparasites of domestic livestock and farmed fish (for example sheep scab mites, poultry mites and sea lice) are also of concern given the increasing strain on the world's food supply. These parasites have become resistant to several classes of pesticide, making control very difficult. Recently, an increasing amount of research has focussed on alternative control methods such as insect growth regulators, biological control using essential oils or fungi, as well as vaccine development against some ectoparasites of medical and veterinary importance.

SUMMARY

Drug resistance is prevalent in all of the ectoparasites discussed in this review. A wide variety of alternative control methods have been identified, however further research is necessary in order for these to be used to successfully control ectoparasitic diseases in the future.

A retrospective study of ectoparasitosis in patients referred to Imam Reza Hospital of Mashhad, Iran

This cross-sectional study was performed on all patients suspected to be suffering from ectoparasites who were referred to the parasitology laboratory of Imam Reza Hospital of Mashhad during 15 years (April 1995 to April 2010). All patients' data were collected from the questionnaires and then analyzed statistically. From 1814 suspected patients to be suffering from ectoparasites, 375 patients had scabies and, 99 suffer from pediculosis. The mean age of patients was 26/18 ± 17/68. The most common age of scabies was 10–19 (27/7%) and pediculosis 0–9(9/6%) (P value = 0.00). The highest incidence of pediculosis was in women (3.6%) and scabies in men (13.7%) (P value = 0.00). Pediculosis is more common in children (9/9%) and scabies in workers (32%)(P value = 0.00). Scabies and pediculosis were more prevalent in patients from Razavi Khorasan Province with 18.7% and 5%, respectively (P value = 0.08).

Clinical phenotype of scabies by age

OBJECTIVE

Scabies has a clinical presentation that seems to vary according to age. We conducted a prospective study with the goal of delineating the clinical presentation of the disease into 3 groups of age: infants, <2 years; children, 2 to 15 years; and adults, >15 years.

METHODS

This trial was a prospective, multicenter observational study in consecutive patients with a confirmed diagnosis of scabies who were seen in 13 French Departments of Dermatology and Pediatric Dermatology between April 2010 and April 2011. A standardized questionnaire was completed for each patient. To identify factors associated with patient age, comparisons between the 3 age groups were conducted by using univariate and multivariate multinomial logistic regression analyses.

RESULTS

A total of 323 individuals were included; the gender ratio (female:male) was 1.2:1. In univariate analysis, infants were more likely to have facial involvement. In multivariate logistic regression, relapse was more frequent in children (odds ratio [OR]: 2.45 [95% confidence interval (CI):1.23-4.88]) and infants (OR: 3.26 [95% CI: 1.38-7.71]). In addition, family members with itch (OR: 2.47 [95% CI: 1.04-5.89]), plantar (OR: 20.57 [95% CI: 7.22-58.60]), and scalp (OR: 16.94 [95% CI: 3.70-77.51]) involvement were also found to be independently associated with the age group <2 years.

CONCLUSIONS

There is a specific clinical presentation of scabies in infants and children. Taking into account these specificities may be helpful for the early diagnosis and the identification of cases to prevent the propagation of the disease.

The origin and distribution of human lice in the world

Two genera of lice parasitize humans: Pthirus and Pediculus. The latter is of significant public health importance and comprises two ecotypes: the body louse and the head louse. These ecotypes are morphologically and genetically notably similar; the body louse is responsible for three infectious diseases: Louse-borne epidemic typhus, relapsing fever, and trench fever. Mitochondrial DNA studies have shown that there are three obviously divergent clades of head lice (A, B and C), and only one clade of body lice is shared with head lice (clade A). Each clade has a unique geographic distribution. Lice have been parasitizing humans for millions of years and likely dispersed throughout the World with the human migrations out of Africa, so they can be good markers for studying human evolution. Here, we present an overview of the origin of human lice and their role in vector pathogenic bacteria that caused epidemics, and we review the association between lice clades and human migrations.

Norwegian crusted scabies: an unusual case presentation

Scabies is a contagious condition that is transmitted through direct contact with an infected person and has been frequently associated with institutional and healthcare-facility outbreaks. The subtype Norwegian crusted scabies can masquerade as other dermatologic diseases owing to the heavy plaque formation. Successful treatment has been documented in published reports, including oral ivermectin and topical permethrin. Few case studies documenting the treatment of Norwegian crusted scabies have reported the use of surgical debridement as an aid to topical and/or oral treatment when severe plaque formation has been noted. A nursing home patient was admitted to the hospital for severe plaque formation of both feet. A superficial biopsy was negative for both fungus and scabies because of the severity of the plaque formation on both feet. The patient underwent a surgical, diagnostic biopsy of both feet, leading to the diagnosis of Norwegian crusted scabies. A second surgical debridement was then performed to remove the extensive plaque formation and aid the oral ivermectin and topical permethrin treatment. The patient subsequently made a full recovery and was discharged back to the nursing home. At 2 and 6 months after treatment, the patient remained free of scabies infestation, and the surgical wound had healed uneventfully. The present case presentation has demonstrated that surgical debridement can be complementary to the standard topical and oral medications in the treatment of those with Norwegian crusted scabies infestation.

Nodular scabies: a classical case report in an adolescent boy

This case report presents a classical case of nodular scabies in a 12 year boy who complained of itching for 20-21 days before presentation to the hospital. Application of Betnovate ointment (Betamethasone valerate 0.1 %) before presentation to the hospital had provided only 2-3 days of relief from itching. Dermatological examination revealed skin colored to erythematous papule of 3-4 mm on the body with predilection for web space of fingers and flexural areas and nodules on the scrotum and groin. Based on this, clinical diagnosis of scabies with nodular scabies was made on the child. The scraping obtained from the web-space of the child showed mite under the light microscope, which confirms the diagnosis. Treatment with topical permethrin 5 % lotion resulted in 50-70 % subsidence of itching within a day, and improvement in impetigo lesions of his father in 5 days. However, the scrotal and groin nodular lesion of the child persisted with severe itching. Treatment with topical steroid and tacrolimus 0.1 % ointment did not show much improvement. Intralesional injection of triamcinolone (5 mg/ml) on the nodule resulted in 30-40 % subsidence in itching and 50-60 % reduction in the size of the lesion over 2-3 weeks.

A papulopustular, vesicular, crusted rash in a 4-week-old neonate

Scabies is commonly seen worldwide, in its usual classic form when afflicting older children and adults. However, neonatal scabies is described as its own entity in the literature. We present a case of a 4-week-old infant with a generalized papulopustular, vesicular, and crusted rash who was diagnosed with scabies. We contrast the differing clinical features of neonatal and classic scabies, describe possible mimickers of this diagnostic dilemma, and review current treatment options available for scabies in this very young age group.

Designing randomized-controlled trials to improve head-louse treatment: systematic review using a vignette-based method

Head-louse infestation remains a public health problem. Despite published randomized-controlled trials, no consensus-based clinical practice guidelines for its management emerged because of the heterogeneity of trial methodologies. Our study was undertaken to attempt to find an optimal trial framework: minimizing the risk of bias, while taking feasibility into account. To do so, we used the vignette-based method. A systematic review first identified trials on head-louse infestation; 49 were selected and their methodological constraints assessed. Methodological features were extracted and combined by arborescence to generate a broad spectrum of potential designs, called vignettes, yielding 357 vignettes. A panel of 48 experts then rated one-on-one comparisons of those vignettes to obtain a ranking of the designs. Methodological items retained for vignette generation were income level of the population, types of treatments compared, randomization unit, blinding, treatment-administration site, diagnosis method and criteria, and primary outcome measure. The expert panel selected vignettes with cluster randomization, centralized treatment administration, and blinding of the outcome assessor. The vignette method identified optimal designs to standardize future head-louse treatment trials, thereby obtaining valid conclusions and comparable data from future trials, and appears to be a reliable way to generate evidence-based guidelines.

Diagnosis, prevention, and treatment of scabies

Scabies remains a public health problem, especially in developing countries, with a worldwide incidence of approximately 300 million cases each year. Prolonged skin-to-skin contact is necessary to allow the transmission of the causative mite, Sarcoptes scabiei. Classic scabies presents with burrows, erythematous papules, and generalized pruritus. Clinical variants include nodular scabies and crusted scabies, also called Norwegian scabies. The diagnosis is based mainly on history and physical examination, but definitive diagnosis depends on direct visualization of the mites under microscopy. Alternative diagnostic methods include the burrow ink test, video-dermatoscopy, newly serologic tests like PCR/ELISA, and specific IgE directed toward major mite components. Treatment of scabies consists of either topical permethrin or oral ivermectin, although the optimal regimen is still unclear.

[Urological dermatosis]

Urologists are often confronted with venereal and dermatological diseases during clinical evaluation of the external genitals. Dermatosis of the male genitalia ranges from infectious (viral and bacterial) lesions and inflammatory conditions to neoplastic alterations. There are also more general skin diseases (e.g. psoriasis) which occur as genital manifestations. In this case they often show unusual characteristics or the genitalia might be involved only incidentally. This review highlights the clinical diagnosis and therapy of the most common genital skin disorders and demonstrates the medical features.

Molecular survey of knockdown resistance to pyrethroids in human scabies mites

There are growing concerns about the emergence of resistance of Sarcoptes scabiei to permethrin and other pyrethroid derivatives. Sarcoptes scabiei mites collected from 40 patients visiting two hospitals near Paris, France, were genotypically characterized considering two parts of their voltage-sensitive sodium channel gene. No nucleotide polymorphism resulting in a codon change at codon 733 or other positions associated with knockdown resistance in other arthropods has been identified. These data may establish a reference line for future surveys of the susceptibility of S. scabiei in the area.

Skin diseases in patients with primary psychiatric conditions: a hospital based study

Background: Although the relationship between skin diseases in patients with primary psychiatric conditions is important for patient management, studies on this issue are limited.

Objective: To detect the frequency and type of cutaneous disorders among patients with primary psychiatric conditions.

Subjects and methods: This analytic cross-sectional study was conducted on a total of 400 subjects – 200 patients with primary psychiatric disorders and 200 age and sex matched individuals free from primary psychiatric disorders. Patients included in the study were diagnosed according to The Diagnostic and Statistical Manual of Mental Disorders (DMS IV) Criteria. A specially designed questionnaire including socio-demographic data, medical history, family history and dermatological examination was applied. The data were statistically analyzed.

Results: There was a significant statistical increase in the prevalence of skin diseases in general and infectious skin diseases in particular in psychiatric patients compared with non-psychiatric patients (71.5% versus 22%, P < 0.001) and (48% versus 11%, P < 0.001), respectively. Parasitic infestations (42.7%) were the most common infectious skin diseases in psychiatric patients (P < 0.001). Infectious skin diseases in psychiatric patients were seen most in patients diagnosed with schizophrenia (83.6%) and least in obsessive compulsive disorders (30%)(P < 0.001). Psychogenic skin disorders were found in 8.4% of psychiatric patients with skin diseases; delusional parasitosis was the most common (50%).

Conclusion: Health education of psychiatric patients and/or of their caregiver and periodic monthly inspection of psychiatric patients are highly indicated for the prevention and control of infectious skin diseases in primary psychiatric patients.

Activity of tea tree oil and nerolidol alone or in combination against Pediculus capitis (head lice) and its eggs

Head lice infestation is an emerging social problem in undeveloped and developed countries. Because of louse resistance increasing, several long-used insecticidal compounds have lost their efficacy, and alternatives, such as essential oils, have been proposed to treat this parasitic infestation. The present study investigated the efficacy of two natural substances: tea tree (Melaleuca alternifolia) oil and nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol) against lice and its eggs. Products were used alone and in combination (ratio 1:1 and 1:2) from 8 % dilution. The in vitro effect of natural substances at different concentrations were evaluated against 69 head lice (adults and nymphs) and 187 louse eggs collected from school children in Chieti-Pescara (Central Italy) over a 6-month period. The lice mortality was evaluated for 24 h by a stereo light microscope. The ovicidal activity was monitored by microscopic inspections for 15 days. Tea tree oil was more effective than nerolidol against head lice with 100 % mortality at 30 min and 1 % concentration. On the contrary, nerolidol expressed a more pronounced ovicidal activity inducing the failure of 50 % of the eggs to hatch at 1 % concentration after 4 days; the same effect was achieved by using a twice concentration of tea tree oil. The association of the two substances both in ratios 1:1 and 1:2 combined efficaciously their insecticidal and ovicidal effect; in particular, the ratio 1:2 (tea tree oil 0.5 % plus nerolidol 1 %) acted producing both the death of all head lice at 30 min and the abortive effect of louse eggs after 5 days. These results offer new potential application of natural compounds and display a promising scenario in the treatment of pediculosis resistant cases. The development of novel pediculicides containing essential oils could be, in fact, an important tool to control the parasitic infestation.

Insecticide resistance in head lice: clinical, parasitological and genetic aspects

Insecticide treatment resistance is considered to be a major factor in the increasing number of infestations by head lice. The large insecticide selection pressure induced by conventional topical pediculicides has led to the emergence and spread of resistance in many parts of the world. Possible mechanisms of resistance include accelerated detoxification of insecticides by enzyme-mediated reduction, esterification, oxidation that may be overcome by synergistic agents such as piperonyl butoxide, alteration of the binding site, e.g. altered acetylcholinesterase or altered nerve voltage-gated sodium channel, and knockdown resistance (kdr). Clinical, parasitological and molecular data on resistance to conventional topical pediculicides show that treatments with neurotoxic insecticides have suffered considerable loss of activity worldwide. In particular, resistance to synthetic pyrethroids has become prominent, probably because of their extensive use. As other treatment options, including non-insecticidal pediculicides such as dimeticone, are now available, the use of older insecticides, such as lindane and carbaryl, should be minimized, owing to their loss of efficacy and safety concerns. The organophosphorus insecticide malathion remains effective, except in the UK, mostly in formulations that include terpineol.

Scabies in the developing world--its prevalence, complications, and management

Scabies remains one of the commonest of skin diseases seen in developing countries. Although its distribution is subject to a cycle of infection, with peaks and troughs of disease prevalence, this periodicity is often less obvious in poor communities. Scabies is a condition that affects families, particularly the most vulnerable; it also has the greatest impact on young children. Largely through the association with secondary bacterial infection caused by group A streptococci and Staphylococcus aureus, the burden of disease is compounded by nephritis, rheumatic fever and sepsis in developing countries. However, with a few notable exceptions, it remains largely neglected as an important public health problem. The purpose of this review is to provide an update on the current position of scabies with regard to its complications and control in resource-poor countries.

Detection of a knockdown resistance mutation associated with permethrin resistance in the body louse Pediculus humanus corporis by use of melting curve analysis genotyping

Louse-borne diseases are prevalent in the homeless, and body louse eradication has thus far been unsuccessful in this population. We aim to develop a rapid and robust genotyping method usable in large field-based clinical studies to monitor permethrin resistance in the human body louse Pediculus humanus corporis. We assessed a melting curve analysis genotyping method based on real-time PCR using hybridization probes to detect the M815I-T917I-L920F knockdown resistance (kdr) mutation in the paraorthologous voltage-sensitive sodium channel (VSSC) α subunit gene, which is associated with permethrin resistance. The 908-bp DNA fragment of the VSSC gene, encoding the α subunit of the sodium channel and encompassing the three mutation sites, was PCR sequenced from 65 lice collected from a homeless population. We noted a high prevalence of the 3 indicated mutations in the body lice collected from homeless people (100% for the M815I and L920F mutations and 56.73% for the T917I mutation). These results were confirmed by melting curve analysis genotyping, which had a calculated sensitivity of 100% for the M815I and T917I mutations and of 98% for the L920F mutation. The specificity was 100% for M815I and L920F and 96% for T917I. Melting curve analysis genotyping is a fast, sensitive, and specific tool that is fully compatible with the analysis of a large number of samples in epidemiological surveys, allowing the simultaneous genotyping of 96 samples in just over an hour (75 min). Thus, it is perfectly suited for the epidemiological monitoring of permethrin resistance in human body lice in large-scale clinical studies.

Permethrin and malathion resistance in head lice: results of ex vivo and molecular assays

BACKGROUND

Treatment of head lice infestation relies on the application of topical insecticides. Overuse of these products has led to the emergence of resistance to pyrethroids and malathion worldwide. Permethrin resistance in head lice is mostly conferred by the knockdown resistance (kdr) trait.

OBJECTIVE

To evaluate the occurrence of permethrin- and malathion-resistant head lice in Paris.

METHODS

A prospective survey was conducted in 74 elementary schools. Live lice collected on schoolchildren were randomly selected and submitted to ex vivo bioassays or underwent individual DNA extraction. A fragment of kdr-like gene was amplified and compared with wild-type sequences.

RESULTS

Live head lice were detected in 574 children. Ex vivo assays showed no surviving lice after a 1-hour contact with malathion while most lice died after a 1-hour exposure to permethrin and piperonyl butoxide (85.7%, 95% confidence interval [CI]: 83.9-87.5). Among the 670 lice with workable DNA sequences, 661 lice (98.7%, 95% CI 97.7-99.3) had homozygous kdr mutations.

LIMITATIONS

The findings of this large-scale survey of the occurrence of insecticide-resistant head lice indicated a major insecticide pressure in the study population, but it was not sufficient to draw conclusions about other populations. The presence of T917I-L920F mutations in kdr gene may not correlate with treatment failure in prospective studies.

CONCLUSION

The high occurrence of kdr mutant allele suggests that insecticide resistance was already strongly established in the studied population. This finding must be interpreted with caution as it may not be predictive of treatment failure.

Human louse-transmitted infectious diseases

Several of the infectious diseases associated with human lice are life-threatening, including epidemic typhus, relapsing fever, and trench fever, which are caused by Rickettsia prowazekii, Borrelia recurrentis, and Bartonella quintana, respectively. Although these diseases have been known for several centuries, they remain a major public health concern in populations living in poor-hygiene conditions because of war, social disruption, severe poverty, or gaps in public health management. Poor-hygiene conditions favour a higher prevalence of body lice, which are the main vectors for these diseases. Trench fever has been reported in both developing and developed countries in populations living in poor conditions, such as homeless individuals. In contrast, outbreaks of epidemic typhus and epidemic relapsing fever have occurred in jails and refugee camps in developing countries. However, reports of a significantly high seroprevalence for epidemic typhus and epidemic relapsing fever in the homeless populations of developed countries suggest that these populations remain at high risk for outbreaks of these diseases. Additionally, experimental laboratory studies have demonstrated that the body louse can transmit other emerging or re-emerging pathogens, such as Acinetobacter baumannii and Yersinia pestis. Therefore, a strict survey of louse-borne diseases and the implementation of efficient delousing strategies in these populations should be public health priorities.

European guideline for the management of pediculosis pubis, 2010

Transmission of the crab louse Phthirus pubis generally occurs by close body contact. Diagnosis is usually clinical and screening for other sexually transmitted infections (STIs) is indicated. While most evidence is extrapolated from studies of head lice treatments, topical pediculicides are recommended and treatment of sexual contacts is indicated.