Current treatments for scabies and pediculosis

Scabies and lice have afflicted man since ancient times. Permethrin is generally the treatment of choice for head lice and scabies, because of its residual effect. Toxicity and absorption are minimal. Ivermectin should be reserved for cases where permethrin fails.     

Ectoparasitic sexually transmitted diseases: scabies and pediculosis

Scabies and pediculosis are diagnosed on an almost daily basis in many dermatology offices. Whether the patient seeks medical attention because of the often unbearable itch of scabies or because of the fear of lice infestations, the physician should be on the lookout for these ectoparasitic infestations. Secondary bacterial infection, resistance to medication, and the risk of spread of the infestations to family members and other close contacts may complicate the problem. Patients frequently have to battle the myths, prejudices, and even shame that are associated with such infestations.     

Treatment of scabies and pediculosis: Facts and controversies

Unlike many other skin diseases, success or failure of therapy of ectoparasitic infestation depends much more on how to use the topical preparation and whom we treat than on which scabicide or pediculicides to use. The diagnosis of scabies should no longer rely on the rather uncommon and unpractical sign of finding a burrow or the number of parasites per infected patient. Most infested individuals have been shown to have several-fold more acari than the oft-quoted average of 12 adult acari per infected patient that appears in most of our textbooks (stemming from Mellanby's work). Contrary to what Mellanby taught us, we know that indirect transmission (ie, without personal contact) does occur. As to which agent to use, the winner remains undeclared at present. Although indirect contact transmission of hair lice has been clarified after thousands of years of infestation, there are still numerous questions, uncertainties, disagreements, and controversies on the subject; for example, we know that lice survive immersion in water but are probably not transmitted in swimming pools. There is no consensus on the best or most correct way to diagnose lice, nor is the problem of resistance resolved. We do not recommend a “no-nit” policy.     

Factors associated with pediculosis pubis and scabies.

OBJECTIVE--To ascertain factors associated with genital pediculosis and scabies infestations among attenders at an STD clinic. DESIGN--Cross sectional assessment of potential risk factors by multiple logistic regression. SETTING--A central city sexually transmitted diseases (STD) clinic in Adelaide, South Australia. SUBJECTS--All men and women patients attending from 1988 to 1991. RESULTS--Pediculosis pubis was diagnosed in 205 of 12,170 (1.7%) men and 65 (1.1%) of 6125 women, and scabies in 56 (0.5%) men and 6 (0.1%) women attending an STD clinic from 1988-1991. Independent risk factors by multivariate analysis for pediculosis pubis in women were pregnancy (odds ratio (OR) = 2.3), sex outside the state (OR = 2.2) and age under 25 (OR = 2.0). Many factors were associated with pediculosis pubis in men, including no steady partner (OR = 1.4), multiple partners (OR = 1.6), being unmarried (OR = 2.0) and homosexual behaviour (OR = 1.6). None of these factors was associated with scabies infestation which was strongly associated with being Aboriginal (OR = 6.8) and being unemployed (OR = 2.5). CONCLUSION--In this setting scabies appears to be determined by socioeconomic factors and pediculosis pubis predominantly by sexual activity factors.     

Treatment of scabies and pediculosis with lindane preparations: an evaluation

Risks and benefits involved in the use of lindane preparations for the treatment of scabies and head louse infestations are evaluated. Although lindane per si is moderately toxic, capable of inducing neurotoxic and hemotoxic effects, there is little evidence that the preparations used in the treatment of scabies and pediculosis give rise to toxic symptoms when applied according to directions. Current evidence does not support the view that lindane is intrinsically carcinogenic, although very high doses have induced hepatomas in mice. It is concluded that the benefits obtained in the use of lindane as a scabicide and pediculicide outweigh risks involved in its use for these purposes. Comparison with other preparations available for the control of scabies and pediculosis indicate that lindane is probably the most effective scabicide, although it also shows the greatest toxic potential. Malathion and pyrethrin preparations seem equally effective against head lice. Suggestions for even safer use of lindane are discussed.     

Pyrethrin and pyrethroid (permethrin) in the treatment of scabies and pediculosis

The history and development of pyrethrum, the natural pyrethrins and synthetic pyrethroids and their insecticidal properties, chemical structure and toxic and allergic side-effects are reported. Permethrin is stressed as a photostable insecticide that is very effective against a large variety of insects and mites with low mammalian toxicity and virtually no allergic side-effects. Only 10-20 min after application, permethrin (1% cream rinse or 0.5% in ethanol) proved to be safe, reliable and cosmetically acceptable in the treatment of infestations with head lice and the prevention of reinfestations, and also in failures with lindane owing to the development of tolerance in the lice. The same was true of 5% permethrin cream (2.5% in children below 5 years of age) used in the treatment of scabies. Permethrin is absorbed percutaneously in only small amounts, is metabolized rapidly in the skin and excreted in the urine. A single "head to toe" application is ideal for eradication programmes allowing lice to be targetted and the prevalence of secondary bacterial infections decreased at the same time. Benzyl benzoate has an irritant potential, and lindane has been reported to exert CNS toxicity in a few anecdotal cases, in particular in small children or after repeated applications in patients with scabies crustosa, and permethrin was distinctly superior to both of these. This is documented by the results obtained in the treatment of 48 children and 56 adults suffering from scabies. Permethrin is recommended in scabies therapy in premature infants, small children, patients with seizures and neurological complications, in treatment failures with lindane entailing the need to repeat the therapy, in scabies crustosa and in pregnant women and nursing mothers.     

Epidemiology and morbidity of scabies and pediculosis capitis in resource-poor communities in Brazil

BACKGROUND: Pediculosis capitis and scabies are common parasitic skin diseases, especially in resource-poor communities, but data on epidemiology and morbidity are scanty. OBJECTIVES: To assess the prevalence, seasonal variation and morbidity of pediculosis capitis and scabies in poor neighbourhoods in north-east Brazil. METHODS: The study comprised cross-sectional surveys of a representative population of an urban slum (n = 1460) in Fortaleza, the capital of Ceará State (Brazil) and a fishing community 60 km south of the city (n = 605). Study participants were examined for the presence of scabies and pediculosis capitis. In a longitudinal study in the slum, variation of prevalence in different seasons of the year was assessed. RESULTS: Prevalence of pediculosis capitis was 43.4% in the slum and 28.1% in the fishing community. Children aged 10-14 years and females were most frequently affected. Scabies was present in 8.8% of the population in the slum and in 3.8% of the population in the fishing community. There was no consistent pattern of age distribution. Superinfection was common in patients with scabies, and cervical lymphadenopathy in patients with pediculosis capitis. Multivariate analysis showed that age < or = 15 years, being of female sex and living in the urban slum were independent factors contributing to the simultaneous coinfestation with pediculosis capitis and scabies. The longitudinal data from the urban slum showed a characteristic seasonal variation of pediculosis capitis, but no fluctuation of scabies. CONCLUSIONS: Pediculosis capitis and scabies are hyperendemic in the study areas and are associated with considerable morbidity. There is an urgent need to develop control measures for these parasitic skin diseases in resource-poor communities. This is the first community-based study describing in detail the epidemiology and morbidity of scabies and head lice infestation in Brazil.     

Plica polonica in association with pediculosis capitis and scabies - a case report

Plica polonica is a rare disorder of hair in which groups of hair shafts become irreversibly entangled, forming a matted, malodorous and encrusted, sticky, moist mass. Various predisposing factors are known to cause this condition. We report one such case associated with pediculosis capitis and scabies.     

Scabies and pediculosis

Although scabies and pediculosis are difficult and widespread problems, there are many effective treatments available. Dermatologists play a major role in educating the public in prevention and diagnosis. Although patients are more aware and well informed of the infections because of the Internet and other sources, practitioners are often the most important source of information and treatment in helping to eradicate this worldwide problem.     

Itch and brain

Itch is an unpleasant somatic sensation that evokes the urge to scratch. Chronic itch is a severe problem that diminishes quality of life. There are many patients suffering from chronic itch across the world. The brain is the final terminal to receive itch‐related signals from the body and plays an important role in perceiving the itch sensation. Thus, to understand the cerebral mechanism of itch perception and how this mechanism differs between healthy subjects and chronic itch patients is important for advancing our understanding on the pathophysiology of chronic itch. Itch is suppressed by scratching or applying painful stimuli. The pleasurable sensation evoked by scratching an itch increases the urge to scratch. Viewing others in itch or imagining the itch sensation may evoke real itch sensations and the scratching response. To understand the mechanisms responsible for these phenomena may provide useful information for the development of treatment of itch and advance our understanding of the cerebral mechanism of itch and scratch. Several functional brain imaging studies have addressed these issues and reported interesting findings. In this review article, the authors discussed the findings of previous studies and how they have advanced our understanding of the central mechanisms of itch, scratch and chronic itch.     

Generalized pediculosis corporis

A case of generalized pediculosis corporis is presented. Microscopic study of sectioned hairs stained with hematoxylin and eosin and of hairs under polarized light allowed identification of larval content and eggs. The value of microscopic examination of hairs is shown.     

Itch and pain

The discovery of a specialized neuronal pathway for itch has markedly improved our understanding of itch processing under physiological conditions. However, the complex interactions of pain and itch are only partly understood. This review focuses on the neurophysiological mechanisms involved in clinical and experimental itch conditions. There is emerging evidence that similar patterns of peripheral and central sensitization occur in chronic pain and chronic itch conditions. It will be of major interest to reveal whether the underlying mechanism for sensitization in the itch and pain pathways are also similar, as this might have major implications for therapy.     

Itch and atopic dermatitis: an overview

Itching is the hallmark of atopic dermatitis, and a vicious itch-scratch circle is easily established. Itching and scratching are important factors in the maintenance of symptoms and can have a significant impact on the sufferer's quality of life. The pathophysiology of itch in atopic dermatitis is still not understood. Unlike in urticaria, histamine is not considered to be a major pruritogen in atopic dermatitis. In fact, the peripheral pruritogens and their cellular origin(s) still remain to be identified in this disease. Various treatments are used to relieve the skin inflammation, itching, and scratching in patients with atopic dermatitis, but no specific antipruritic therapy is available. However, several nonspecific therapies can effectively break the vicious itch-scratch circle. The use of topical corticosteroids and emollients and the elimination of individual trigger factors are still first-line measures.