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Scabies and pediculosis: neglected diseases to highlight

2012; Elsevier BV; Volume: 18; Issue: 4 Linguagem: Inglês

10.1111/j.1469-0691.2012.03791.x

1469-0691

O. Chosidow,

Dermatological diseases and infestations

Ectoparasites or epidermal parasites are responsible for a heterogeneous group of infections of the external layer of the skin. Scabies and pediculosis (capitis, corporis, and pubis) are among the most common (despite the re-emergence of diseases such as that caused by Pyemotes ventricosus and bed bug infections) and share well-known features [1Chosidow O Scabies and pediculosis.Lancet. 2000; 355: 819-826Abstract Full Text Full Text PDF PubMed Scopus (389) Google Scholar, 2Chosidow O Clinical practices. Scabies.N Engl J Med. 2006; 354: 1718-1727Crossref PubMed Scopus (377) Google Scholar, 3Heukelbach J Feldmeier H Scabies.Lancet. 2006; 367: 1767-1774Abstract Full Text Full Text PDF PubMed Scopus (270) Google Scholar]: (i) worldwide prevalence (involving millions of people annually); (ii) parasites inducing skin lesions directly, such as with urticarial papules, and indirectly as a result of itching and hypersensitivity to parasites, thus leading to a genuine nuisance and sometimes daily nightmares or, in some cases, skin superinfection; and (iii) treatment based on good entomological knowledge of the parasite and practical considerations (for example, most available treatments do not act on eggs and should be repeated, depending on the life cycle of the parasites [4Mumcuoglu KY Effective treatment of head louse with pediculicides.J Drugs Dermatol. 2008; 5: 451-452Google Scholar]). With this special issue of CMI, we provide an overview of four major points that affect knowledge and/or management of scabies and pediculosis for infectious disease specialists, microbiologists, and dermatologists, as well as general practitioners and healthcare workers. This issue is more than welcome, as scabies and pediculosis (and ectoparasitoses in general) are often neglected by many health providers. Hay et al. [5Hay RJ Steer AC Engelman D Walton S Scabies in the developing world–its prevalence, complications, and management.Clin Microbiol Infect. 2012; 18: 313-323Abstract Full Text Full Text PDF PubMed Scopus (186) Google Scholar] summarize the current knowledge about scabies in the developing world, with a focus on epidemiology, transmission, pathogenesis, clinical manifestations, and treatment. In some countries, the prevalence since 2004 has ranged from 0.4% to 31%, overcrowding being the major factor in transmission. The major burden of scabies is secondary bacterial infection caused by group A streptococci and/or Staphylococcus aureus, sometimes leading to nephritis, rheumatic fever, and sepsis. The authors summarize the main treatment options for scabies, 5% permethrin being the first-line treatment and oral ivermectin being generally reserved for recurrent difficult-to-treat scabies or crusted scabies. Trials with good evidence are lacking [6Strong M Johnstone P Interventions for treating scabies.Cochrane Database Syst Rev. 2007; (CD000320.)PubMed Google Scholar], but Hay et al. [5Hay RJ Steer AC Engelman D Walton S Scabies in the developing world–its prevalence, complications, and management.Clin Microbiol Infect. 2012; 18: 313-323Abstract Full Text Full Text PDF PubMed Scopus (186) Google Scholar] and others [7Currie BJ McCarthy JS Clinical practice. Permethrin and ivermectin for scabies.N Engl J Med. 2010; 362: 717-725Crossref PubMed Scopus (231) Google Scholar] consider the use of ivermectin to be promising for institutional outbreaks and mass administration in highly endemic communities. Hopefully, in the near future, an International Alliance for the Control of Scabies will give proposals and support to better control scabies in the developing world. Boyd and Reed [8Boyd BM Reed DL Taxonomy of lice and their endosymbiotic bacteria in the post‐genomic era.Clin Microbiol Infect. 2012; 18: 324-331Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar] review the taxonomy of lice, given our knowledge of approximately 4500 recognized species of chewing lice and only 540 of sucking lice. The authors summarize the data establishing the taxonomic rank of the human body louse and the phylogenetic relationships of Phtirus and Pediculus. For instance, mitochondrial sequence data have revealed human body lice to be eco-morphs of a single species, which has challenged old concepts of the evolutionary history of parasitic lice. The authors outline the expected and unexpected consequencies of sequencing the human body louse genome. A fascinating section is devoted to endosymbionts of lice, with bacteria being potentially engaged in nutritional provisioning; new data obtained with molecular tools involving supercomputers and metagenomic algorithms have led to interesting discoveries in phylogenetic analysis. Badiaga and Brouqui [9Badiaga S Brouqui P Human louse‐transmitted infectious diseases.Clin Microbiol Infect. 2012; 18: 332-337Abstract Full Text Full Text PDF PubMed Scopus (85) Google Scholar] review louse-borne infectious diseases; in general, only body lice act as vectors for human pathogens. The transmission of disease occurs through the contamination of bite sites by faeces from infected body lice or crushed infected louse bodies. It is of interest that, among the three main diseases transmitted by body lice, two, epidemic typhus and trench fever, were detected in some homeless populations. Moreover, Bartonella quintana was found in head lice in schoolchildren from slums of resource-poor countries but not in those in western countries. Interestingly, experimental laboratory studies showed that the body louse can transmit Acinetobacter baumanii and Yersinia pestis. Indeed, as the authors emphasize, strict surveys, improvements in hygienic conditions and efficient delousing, with active antibiotics if necessary, should be carried out with potential target populations. Finally, Durand et al. [10Durand R Bouvresse S Berdjane Z Izri A Chosidow O Clark JM Insecticide resistance in head lice: clinical, parasitological and genetic aspects.Clin Microbiol Infect. 2012; 18: 338-344Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar] summarize what is known about insecticide resistance in head lice. Clinical and parasitological resistance in head lice was first described in France [11Chosidow O Chastang C Brue C et al.Controlled study of malathion and d‐phenothrin lotions for Pediculus humanus var. capitis‐infested schoolchildren.Lancet. 1994; 344: 1724-1727Abstract PubMed Scopus (132) Google Scholar] from both a randomized controlled trial and ex vivo parasitology test data. Resistance should be suspected when live lice are still present on the head 24 h after application of insecticide. Insecticide resistance has been described worldwide, and is related to large insecticide selection pressure induced by conventional pediculicides such as pyrethroids and malathion. The molecular events that govern the resistance include the recessive kdr trait linked to three point mutations (M8151, T9171, and L920F) in the voltage-gated sodium channel, which are responsible for a lower neurotoxic effect of permethrin on lice. However, phenotype and genotype are not strictly correlated. The authors also cover resistance to malathion and lindane. Dealing with insecticide resistance in head lice is not easy, and medical devices such as bug-busting or dimeticone, or oral ivermectin [12Chosidow O Giraudeau B Cottrell J et al.Oral ivermectin versus malathion lotion for difficult‐to‐treat head lice.N Engl J Med. 2010; 362: 896-905Crossref PubMed Scopus (159) Google Scholar] (not approved in Europe), could be alternatives. In conclusion, scabies and pediculosis affect most countries in the world, developed or undeveloped, with the potential involvement of a large number of individuals or institutions. This special issue, giving an overview of scabies and pediculosis, should provide an impetus for health authorities and physicans to be aware of these neglected diseases. O. Chosidow has received consulting fees from Laboratoire Pierre Fabre and lecture fees from Pohl Boskamp. He received consulting fees from Johnson & Johnson at the time of the ivermectin study (2006).