Circulating IgE in patients with ordinary and crusted scabies

Immune mechanisms in human Sarcoptes scabiei (Acari: Sarcoptidae) infestations

Scabies is a parasitic infestation of human and animal skin caused by different strains of the itch mite, Sarcoptes scabiei. The World Health Organization (WHO) has declared scabies in human as a neglected tropical disease, and today over 200 million people worldwide are affected. The two most commonly reported clinical manifestation of the condition are ordinary (OS) and crusted scabies (CS). CS, which can lead to fatal consequences due to secondary bacterial infections, is mostly observed in immunocompromised subjects but can also, although rarely, be detected in immunocompetent individuals. Innate and adaptive immune system components are involved in protection and pathogenesis of scabies, although with some differences between OS and CS. While the cutaneous immune response is dominated by CD4⁺ T-cells in OS, it is mainly mediated by CD8⁺ T-cells in CS. The two clinical conditions also differ in CD4⁺ T-cell-mediated immune responses with mixed T_H 1/T_H 2 (protective) and T_H 2/T_H 17 (non-protective) immunoprofiles in OS and CS, respectively. Moreover, the development of CS is associated with early immunosuppression that is followed by deleterious immune response to uncontrolled mite proliferation. However, the immune response to scabies still needs further attention due to inconsistent results in the literature. The aim of this study is to attract more attention to this area by summarizing the current literature on innate and adaptive immune responses triggered against S. scabiei mites.

Are humanized IgE reporter systems potential game changers in serological diagnosis of human parasitic infection?

Immunoglobulin E (IgE) is thought to have evolved to protect mammalian hosts against parasitic infections or toxins and plays a central role in the pathogenesis, diagnosis, and therapy of IgE-mediated allergy. Despite the prominence of IgE responses in most parasitic infections, and in stark contrast to its use in the diagnosis of allergy, this isotype is almost completely unexploited for parasite diagnosis. Here, we discuss the perceived or real limitations of IgE-based diagnosis in parasitology and suggest that the recent creation of a new generation of very sensitive cellular IgE-based reporters may represent a powerful new diagnostic platform, but needs to be based on a very careful choice of diagnostic allergens.

Unusual presentation of crusted scabies with osteolysis in immunocompetent

BACKGROUND

Crusted scabies results from a failure of the host immune response to control the proliferation of the scabies mite in the skin, with resulting hyperinfestation and a concomitant inflammatory and hyper-keratotic reaction. However, it has also been recognised in people with no evident immunological deficit.

CASE HISTORY

We present a case report of apparently immunocompetent 16-year-old female presenting with multiple hyperkeratotic vegetating plaques over limbs, excoriated papules over trunk with minimal itching since 2 years without any positive family history. The microscopic examination of the skin scales with potassium hydroxide demonstrated numerous scabies mites and eggs. Histopathology showed hyperkeratosis with multiple mites in stratum corneum. Numerous mites were seen on biopsy of lesion. X-ray showed osteolysis of distal phalanges secondary to chronic pressure. Repeated topical treatments with permethrin and oral ivermectin led to the considerable resolution of her lesions.

CONCLUSION

We present a rare case of crusted scabies with osteolysis in an immunocompetent female.

Clinical diagnosis and treatment of scabies, a neglected tropical disease

Scabies is a parasitic infestation of the skin caused by the mite Sarcoptes scabiei var. hominis. It is common in tropical areas, including the sub-tropical areas of Southern Africa. Predisposing factors are overcrowding, poor personal hygiene, low socio-economic standards and impaired host immunity. Although it can occur at any age, scabies is commonly seen in children and young adults. It is not a fatal disease; however, it can cause severe morbidity and poor quality of life. Scabies can complicate with pyoderma which may result in post-streptococcal glomerulonephritis. There are two clinical variants, classic scabies and the much rarer crusted scabies (Norwegian scabies).

Comparative analysis of the allergenic characteristics and serodiagnostic potential of recombinant chitinase-like protein-5 and -12 from Sarcoptes scabiei

Background

Scabies is caused by burrowing of the mite Sarcoptes scabiei into the stratum corneum. Currently, diagnosis via routine skin scraping is very difficult, and information on the allergenic identification of S. scabiei remains limited.

Methods

We performed comparative analysis of the serological diagnostic potential of recombinant S. scabiei chitinase-like protein-5 (rSsCLP5) and recombinant S. scabiei chitinase-like protein-12 (rSsCLP12) by measuring the levels of serum-specific IgG and IgE antibodies (Abs) as diagnostic markers. In addition, the allergenic characteristics of rSsCLP5 and rSsCLP12 were evaluated using IgE-binding experiments and skin tests.

Results

The IgE Abs-based indirect enzyme-linked immunosorbent assay (ELISA) methods showed high sensitivity and specificity: the rSsCLP5-based assay had 93.5% sensitivity and 94.4% specificity; the rSsCLP12-based assay had 100% sensitivity and 98.1% specificity. The specific IgE Abs in infested mouse sera could bind rSsCLP5 and rSsCLP12. In skin tests, rabbits in the rSsCLP5 and rSsCLP12 groups and positive control (histamine) groups exhibited allergic reactions. Most test sites in the rSsCLP12 group had edema, bleeding spots, and even ulcers or scabs, but such allergy symptoms were rare in the rSsCLP5 group. Moreover, the allergic history rabbit group had more severe allergic reactions and lower levels of IgE Abs compared to the healthy rabbit group in the same protein group.

Conclusions

These findings validate the use of IgE Abs to rSsCLP5 and rSsCLP12 as potentially useful markers for diagnosing scabies. Moreover, both rSsCLP5 and rSsCLP12 have allergenic properties, and the potential allergen rSsCLP12 is a stronger allergen than rSsCLP5.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04654-0.

Scabies: A comprehensive review and current perspectives

Human scabies is a contagious skin infestation caused by the parasitic mite Sarcoptes scabiei var. hominis. It is a common skin disease worldwide that occurs not only in the underprivileged sections of society but also in developed countries. In 2009, World Health Organization (WHO) recognized scabies as "neglected tropical disease (NTD)" or NTD thus emphasizing the need for community awareness and proper treatment strategies. This review attempts to summarize the varied clinical presentation of the disease and describes the advances in diagnosis and management including the ongoing search for novel agents to overcome the problems associated with conventional treatments. The literature research includes peer-reviewed articles (clinical trials or scientific reviews). Studies were identified by searching electronic databases (MEDLINE and PubMed) till February 2020 and reference lists of respective articles. Only articles published in English language were included.

A review of sarcoptic mange in North American wildlife

The "itch mite" or "mange mite", Sarcoptes scabiei, causes scabies in humans and sarcoptic mange in domestic and free-ranging animals. This mite has a wide host range due to its ability to adapt to new hosts and has been spread across the globe presumably through human expansion. While disease caused by S. scabiei has been very well-studied in humans and domestic animals, there are still numerous gaps in our understanding of this pathogen in free-ranging wildlife. The literature on sarcoptic mange in North American wildlife is particularly limited, which may be due to the relatively limited number of clinically-affected species and lack of severe population impacts seen in other continents. This review article provides a summary of the current knowledge of mange in wildlife, with a focus on the most common clinically-affected species in North America including red foxes (Vulpes vulpes), gray wolves (Canis lupus), coyotes (Canis latrans), and American black bears (Ursus americanus).

A Review of Scabies: An Infestation More than Skin Deep

Human scabies, a common infestation, has a worldwide distribution with a variable impact and presentation depending on the clinical situation. In developed, high-income settings, health institution and residential home outbreaks challenge health and social care services. In resource-poor settings, it is the downstream sequelae of staphylococcal and streptococcal bacteraemia, induced by scratching, which have a significant impact on the long-term health of communities. Over the past decade scabies has been recognised as a “neglected tropical disease” (NTD) by the World Health Organisation, has an accepted practical system of global diagnostic criteria and is being adopted into integrated programmes of mass drug administration for NTDs in field settings. This review seeks to summarise the recent advances in the understanding of scabies and highlight the advocacy and research headlines with their implication for diagnosis and management of outbreaks and individuals. In addition, it will indicate the priorities and questions that remain.

Scabies, crusted (Norwegian) scabies and the diagnosis of mite sensitisation

Scabies is observed with relatively high frequency in Allergy and Dermatology clinics in developing countries where poor sanitary conditions are prevalent and increasingly in some areas of the world with increased immigrant populations. Since the immunological response to scabies mites includes the production of IgE class antibodies to Sarcoptes scabiei allergens which cross-react with Dermatophagoides major allergens Der p 1 and Der p 2, positive immediate-type skin tests to house dust mite extracts should be interpreted cautiously. Additionally, scabies should be included routinely in the differential diagnosis of itchy rashes in patients living in those areas.

Characterization of Sarcoptes scabiei Tropomyosin and Paramyosin: Immunoreactive Allergens in Scabies

Scabies is a human skin disease due to the burrowing ectoparasite Sarcoptes scabiei var. hominis resulting in intense itching and inflammation and manifesting as a skin allergy. Because of insufficient mite material and lack of in vitro propagation system for antigen preparation, scabies is a challenging disease to develop serological diagnostics. For allergen characterization, full-length S. scabiei tropomyosin (Sar s 10) was cloned, expressed in pET-15b, and assessed for reactivity with IgE antibodies from human sera. IgE binding was observed to Sar s 10 with sera collected from subjects with ordinary scabies, house dust mite (HDM)-positive and naive subjects and a diagnostic sensitivity of < 30% was observed. S. scabiei paramyosin (Sar s 11) was cloned, and expressed in pET-28a in three overlapping fragments designated Sspara1, Sspara2, and Sspara3. IgE and IgG binding was observed to Sspara2 and Sspara3 antigens with sera collected from ordinary scabies, and HDM-positive subjects, but no binding was observed with sera collected from naive subjects. Sspara2 displayed excellent diagnostic potential with 98% sensitivity and 90% specificity observed for IgE binding and 70% sensitivity for IgG. In contrast, the diagnostic sensitivity of Sspara3 was 84% for IgE binding and 40% for IgG binding. In combination, Sspara2 and Sspara3 provided an IgE sensitivity of 94%. This study shows that IgE binding to Sspara2 and Sspara3 is a highly sensitive method for diagnosis of scabies infestation in clinical practice. The developed enzyme-linked immunosorbent assay helps direct future development of a specific diagnostic tool for scabies.

Host immune responses to the itch mite, Sarcoptes scabiei, in humans

Scabies is a parasitic disease due to infestation of skin by the burrowing mite Sarcoptes scabiei. Scabies is a major public health problem and endemic in resource poor communities worldwide affecting over 100 million people. Associated bacterial infections cause substantial morbidity, and in severe cases can lead to renal and cardiac diseases. Mite infestation of the skin causes localised cutaneous inflammation, pruritus, skin lesions, and allergic and inflammatory responses are mounted by the host against the mite and its products. Our current understanding of the immune and inflammatory responses associated with the clinical manifestations in scabies is far outweighed by the significant global impact of the disease. This review aims to provide a better understanding of human immune responses to S. scabiei in ordinary and crusted scabies phenotypes.

A review of Sarcoptes scabiei: past, present and future

The disease scabies is one of the earliest diseases of humans for which the cause was known. It is caused by the mite, Sarcoptes scabiei, that burrows in the epidermis of the skin of humans and many other mammals. This mite was previously known as Acarus scabiei DeGeer, 1778 before the genus Sarcoptes was established (Latreille 1802) and it became S. scabiei. Research during the last 40 years has tremendously increased insight into the mite’s biology, parasite-host interactions, and the mechanisms it uses to evade the host’s defenses. This review highlights some of the major advancements of our knowledge of the mite’s biology, genome, proteome, and immunomodulating abilities all of which provide a basis for control of the disease. Advances toward the development of a diagnostic blood test to detect a scabies infection and a vaccine to protect susceptible populations from becoming infected, or at least limiting the transmission of the disease, are also presented.

Identification of antigenic Sarcoptes scabiei proteins for use in a diagnostic test and of non-antigenic proteins that may be immunomodulatory

Background

Scabies, caused by the mite, Sarcoptes scabiei, infects millions of humans, and many wild and domestic mammals. Scabies mites burrow in the lower stratum corneum of the epidermis of the skin and are the source of substances that are antigenic or modulate aspects of the protective response of the host. Ordinary scabies is a difficult disease to diagnose.

Objective

The goal of this project was to identify S. scabiei proteins that may be candidate antigens for use in a diagnostic test or may be used by the mite to modulate the host’s protective response.

Methods

An aqueous extract of S. scabiei was separated by 2-dimensional electrophoresis and proteins were identified by mass spectrometry. A parallel immunoblot was probed with serum from patients with ordinary scabies to identify IgM and/or IgG-binding antigens. The genes coding for 23 selected proteins were cloned into E. coli and the expressed recombinant proteins were screened with serum from patients with confirmed ordinary scabies.

Results

We identified 50 different proteins produced by S. scabiei, 34 of which were not previously identified, and determined that 66% were recognized by patient IgM and/or IgG. Fourteen proteins were screened for use in a diagnostic test but none possessed enough sensitivity and specificity to be useful. Six of the 9 proteins selected for the possibility that they may be immunomodulatory were not recognized by antibodies in patient serum.

Conclusions

Thirty-three proteins that bound IgM and/or IgG from the serum of patients with ordinary scabies were identified. None of the 14 tested were useful for inclusion in a diagnostic test. The identities of 16 proteins that are not recognized as antigens by infected patients were also determined. These could be among the molecules that are responsible for this mite’s ability to modulate its host’s innate and adaptive immune responses.

Scabies, caused by the mite, Sarcoptes scabiei, infects millions of humans, and many wild and domestic mammals. Scabies mites burrow in the lower stratum corneum of the epidermis of the skin and are the source of substances that are antigenic or modulate aspects of the protective response of the host. Ordinary scabies is a difficult disease to diagnose. We identified 50 different proteins produced by S. scabiei, 33 of which bound IgM and/or IgG from the serum of patients with ordinary scabies. A set of 23 recombinant proteins were produced and screened for use in a diagnostic test but none possessed enough sensitivity and specificity to warrant further consideration although some could be among the molecules that are responsible for this mite’s ability to modulate its host’s innate and adaptive immune responses.

Crusted scabies (sarcoptic mange) in four cats due to Sarcoptes scabiei infestation

Four new cases of sarcoptic mange in cats are described. Two cats resided in areas known to be frequented by foxes, another cohabited with a dog recently diagnosed with sarcoptic mange, while the final cat lived with a mixed breed dog that had been treated for sarcoptic mange 7 months previously. Three cases were diagnosed on the basis of characteristic mite size and morphology in skin scraping from representative lesions, situated on the head (two cases) or head and distal hind limbs (one case). Mites were highly mobile and abundant in all instances, and easily detected also in skin biopsy specimens procured from two cases. Eosinophilic inflammation, hyperkeratosis and parakeratosis were prominent in the tissue sections. In the remaining case, the diagnosis was presumptive, based on characteristic lesions, cohabitation with a canine scabies patient and positive response to scabicide therapy. Pruritus was not a prominent clinical feature in any patient and was considered to be absent in three of the four cases. Lesions in three cats with long-standing disease were reminiscent of crusted scabies (synonym: Norwegian scabies, parakeratotic scabies) as seen in human patients. In three cases, in-contact human carriers developed itchy cutaneous papular lesions. Two cases responded promptly to therapy with systemic avermectin drugs, while one responded to topical treatment with lime sulphur and the remaining cat received both a lime sulphur rinse and ivermectin. Sarcoptic mange should be considered in the differential diagnosis of cats with non-pruritic crusting skin diseases, especially when there is contact with foxes or dogs, and when owners have itchy papular lesions.

A Proteomic Analysis of Sarcoptes scabiei (Acari: Sarcoptidae)

The pruritic skin disease scabies is caused by the burrowing of the itch mite Sarcoptes scabiei (De Geer). It is difficult to diagnose this disease because its symptoms often resemble those of other skin diseases. No reliable blood or molecular diagnostic test is available. The aim of this project was to begin to characterize the scabies proteome to identify scabies mite proteins, including those that may be useful in the development of a diagnostic test or vaccine. Various scabies mite extracts were separated by two-dimensional electrophoresis, and 844 Coomassie Blue-stained protein spots were excised, subjected to trypsin digestion, and analyzed by Matrix Assisted Laser Desorption/Ionization Time-Of-Flight/Time-Of-Flight (MALDI-TOF/TOF) mass spectrometry (MS). Tryptic fragment sequences determined by MS were searched against the recently completed S. scabiei annotated genome, leading to the identification of >150 proteins. Only 10 proteins hit to previously identified scabies proteins including actin, tropomyosin, and several ABC transporters. Thirteen proteins had homology to dust mite allergens (members of groups 8, 10, 13, 17, 20, 25, and 28). Most other sequences showed some homology to proteins in other mites and ticks including homologs of calmodulin, calreticulin, lipocalin, and glutathione-S-transferase. These data will now allow the identification of the proteins to which scabies patients produce antibodies, including those that may be good candidates for inclusion in a diagnostic test and vaccine.

The Potential for a Blood Test for Scabies

Background

Scabies afflicts millions of people worldwide, but it is very difficult to diagnose by the usual skin scrape test, and a presumptive diagnosis is often made based on clinical signs such as rash and intense itch. A sensitive and specific blood test to detect scabies would allow a physician to quickly make a correct diagnosis.

Objective

Our objective was to profile the mite-specific antibodies present in the sera of patients with ordinary scabies.

Methods

Sera of 91 patients were screened for Ig, IgD, IgE, IgG and IgM antibodies to S. scabiei, as well as to the house dust mites Dermatophagoides farinae, D. pteronyssinus and Euroglyphus maynei.

Results

45%, 27% and 2.2% of the patients had measurable amounts of mixed Ig, IgG and IgE that recognized scabies mite antigens. However, 73.6% of the scabies patients had serum IgM that recognized scabies proteins, and all except two of them also had IgM that recognized all of the three species of dust mites. No patient had serum antibody exclusively reactive to scabies mite antigens.

Conclusions

Co-sensitization or cross-reactivity between antigens from scabies and house dust mites confounds developing a blood test for scabies.

Scabies, caused by the mite S. scabiei that burrows in the skin of humans, is a contagious skin disease that affects millions of people worldwide. It is a significant public health burden in economically disadvantaged populations, and outbreaks are common in nursing homes, daycare facilities, schools and workplaces in developed countries. It causes significant morbidity, and in chronic cases, associated bacterial infections can lead to renal and cardiac diseases. Scabies is very difficult to diagnose by the usual skin scrape test, and a presumptive diagnosis is often made based on clinical signs such as rash and itch that can mimic other skin disease. A sensitive and specific blood test to detect scabies-specific antibodies would allow a physician to quickly make a correct diagnosis. Our manuscript reports the antibody isotype profiles of the sera of two groups of patients with ordinary scabies (17 from the US and 74 from Brazil) and concludes that such a blood test should be based on circulating IgM type antibodies that do not also recognize antigens of the related and ubiquitous house dust mites. Both are important considerations for research for developing a blood test for the diagnosis of scabies.

Crusted scabies is associated with increased IL-17 secretion by skin T cells

Scabies is an ectoparasitic infestation by the mite Sarcoptes scabiei. Although commonly self-limiting, a fraction of patients develop severely debilitating crusted scabies. The immune mechanisms underlying the development of crusted scabies are unclear, and undertaking longitudinal infection studies in humans is difficult. We utilized a porcine model to compare cellular immune responses in peripheral blood and skin of pigs with different clinical manifestations of scabies (n = 12), and in uninfected controls (n = 6). Although clinical symptoms were not evident until at least 4 weeks post-infestation, the numbers of peripheral IFNγ-secreting CD4(+) T cells and γδ T cells increased in infected pigs from week 1 post-infestation. γδ T cells remained increased in the blood at week 15 post-infestation. At week 15, skin cell infiltrates from pigs with crusted scabies had significantly higher CD8(+) T cell, γδ T cell and IL-17(+) cell numbers than those with ordinary scabies. Peripheral IL-17 levels were not increased, suggesting that localized skin IL-17-secreting T cells may play a critical role in the pathogenesis of crusted scabies development. Given the potential of anti-IL-17 immunotherapy demonstrated for other inflammatory skin diseases, this study may provide a novel therapeutic avenue for patients with recurrent crusted scabies.

Vaccine against scabies: necessity and possibility

Scabies is an infectious disease that is endemic in poorly resourced communities, and also common in industrialized countries. Although the disease, which is caused by infestation of Sarcoptes scabiei, is generally mild, the need for a vaccine against S. scabiei is proposed. The immunological mechanisms that control S. scabiei infection are discussed and the current status of scabies vaccine development reviewed. Future directions for scabies vaccine development are also addressed.

Antibody responses to Sarcoptes scabiei apolipoprotein in a porcine model: relevance to immunodiagnosis of recent infection

No commercial immunodiagnostic tests for human scabies are currently available, and existing animal tests are not sufficiently sensitive. The recombinant Sarcoptes scabiei apolipoprotein antigen Sar s 14.3 is a promising immunodiagnostic, eliciting high levels of IgE and IgG in infected people. Limited data are available regarding the temporal development of antibodies to Sar s 14.3, an issue of relevance in terms of immunodiagnosis. We utilised a porcine model to prospectively compare specific antibody responses to a primary infestation by ELISA, to Sar s 14.3 and to S. scabiei whole mite antigen extract (WMA). Differences in the antibody profile between antigens were apparent, with Sar s 14.3 responses detected earlier, and declining significantly after peak infestation compared to WMA. Both antigens resulted in >90% diagnostic sensitivity from weeks 8-16 post infestation. These data provide important information on the temporal development of humoral immune responses in scabies and further supports the development of recombinant antigen based immunodiagnostic tests for recent scabies infestations.

Increased allergic immune response to Sarcoptes scabiei antigens in crusted versus ordinary scabies

Scabies, a parasitic skin infestation by the burrowing "itch" mite Sarcoptes scabiei, causes significant health problems for children and adults worldwide. Crusted scabies is a particularly severe form of scabies in which mites multiply into the millions, causing extensive skin crusting. The symptoms and signs of scabies suggest host immunity to the scabies mite, but the specific resistant response in humans remains largely uncharacterized. We used 4 scabies mite recombinant proteins with sequence homology to extensively studied house dust mite allergens to investigate a differential immune response between ordinary scabies and the debilitating crusted form of the disease. Subjects with either disease form showed serum IgE against recombinant S. scabiei cysteine and serine proteases and apolipoprotein, whereas naive subjects showed minimal IgE reactivity. Significantly (P < 0.05) greater serum IgE and IgG4 binding to mite apolipoprotein occurred in subjects with crusted scabies than in those with ordinary scabies. Both subject groups showed strong proliferative responses (peripheral blood mononuclear cells) to the scabies antigens, but the crusted scabies group showed increased secretion of the Th2 cytokines interleukin 5 (IL-5) and IL-13 and decreased Th1 cytokine gamma interferon (IFN-gamma) in response to the active cysteine protease. These data confirm that a nonprotective allergic response occurs in the crusted disease form and demonstrate that clinical severity is associated with differences in the type and magnitude of the antibody and cellular responses to scabies proteins. A quantitative IgE inhibition assay identified IgE immunoreactivity of scabies mite antigens distinct from that of house dust mite antigens, which is potentially important for specific scabies diagnosis and therapy.

Neonatal Norwegian scabies: three cooperating causes

BACKGROUND

Norwegian or crusted scabies is seldom reported in infancy, usually in immune deficient patients.

MAIN OBSERVATIONS

We report a case of an infant affected by atopic dermatitis since birth. The patient was ineffectively treated with topical and systemic steroids for several weeks for the insurgence of cutaneous xerosis and erithema. Clinical inspection and optical microscopic examination of skin scraped scales leaded to the diagnosis of crusted scabies. The physiological inability to scrapping reaction, the immunological profile deriving from atopy and finally iatrogenic immunodepression cooperating to conduce to crusted scabies.

CONCLUSION

In our case iatrogenic immunosuppression, atopic dermatitis and the absence of skin scraping reaction because of the very young age might have contributed to the unusual presentation of scabies. This case suggests considering possible alternative diagnosis of scabies in the failure of the treatment for atopic eczema.

Modulation of human dermal microvascular endothelial cells by Sarcoptes scabiei in combination with proinflammatory cytokines, histamine, and lipid-derived biologic mediators

The ectoparasitic mite, Sarcoptes scabiei, produces molecules that depress initiation of host inflammatory and immune responses. Some of these down-regulate expression of adhesion molecules or secretion of chemokines or cytokines on and by cultured dermal endothelial cells (HMVEC-D). This study was undertaken to determine if the response of HMVEC-D to scabies is altered in the presence of various proinflammatory cytokines (tumor necrosis factor alpha and interleukins 1alpha, 1beta and 6), histamine, and lipid-derived mediators (prostaglandins D2 and E2, leukotriene B4, platelet activation factor) that likely occur in scabietic lesions in vivo. Scabies extract down-regulated the TNFalpha-induced expression of VCAM-1 by HMVEC-D and this down-regulation still occurred in the presence of the other proinflammatory cytokines, histamine or the lipid-derived mediators. Scabies inhibited the IL-1alpha and IL-1beta-induced secretion of IL-6, while a combination of scabies and histamine or LTB4 reduced the TNFalpha-induced secretion of IL-6. Scabies extract inhibited secretion of IL-8. Histamine, PGD2, PGE2, LTB4, PAF, and IL-6 alone had no effect on this inhibition, but the scabies-induced inhibition of IL-8 secretion was reduced in a dose-dependent fashion in the presence of IL-1alpha and IL-1beta.

[Scabies]

Scabies is an infectious disease caused by Sarcoptes scabiei var. hominis. The disease is mainly transmitted by close personal contact. The primary clinical picture is characterized by burrows at typical areas as well as severe pruritus, while secondarily a rather non-specific exanthema can be observed. The detection of mites or mite products (eggs, feces) confirms the diagnosis; dermatoscopy may facilitate the diagnosis. First choice therapy for most variants of scabies is topical permethrin. Oral administration of ivermectin is recommended for some special indications. In the following article, the current knowledge about epidemiology, biology, immunology, clinical appearance, diagnostic procedures and therapy of scabies is reviewed.

Allergenicity of the Madagascar hissing cockroach

BACKGROUND

The Madagascar hissing cockroach (Gromphadorhina portentosa) has become popular as a pet and as an educational tool in classrooms, zoos, and museums.

OBJECTIVE

To determine whether proteins in G. portentosa are allergens and whether these allergens cross-react with those of other cockroach species.

METHODS

Sera from cockroach-sensitive individuals and control subjects were used to probe immunoblots for the presence of circulating IgE that bound to proteins present in extracts of 4 cockroach species.

RESULTS

Serum from an individual sensitized to G portentosa had circulating IgE that bound to proteins in extracts of all 4 cockroach species. Eight of 15 Blatella germanica-sensitized patients had IgE that bound to proteins in extracts prepared from G portentosa. Rabbit antiserum to Periplaneta americana and to Bla g 1 also contained antibody that bound to proteins in G. portentosa extract, demonstrating antigenic cross-reactivity among these cockroach species.

CONCLUSIONS

Allergists, teachers, parents, and patients should be aware that sensitization and allergic reactions to the Madagascar hissing cockroach can occur. Caution should be taken if these exotic cockroaches are used in educational exercises in schools, museums, and zoos to protect predisposed individuals.

Problems in diagnosing scabies, a global disease in human and animal populations

Scabies is a worldwide disease and a major public health problem in many developing countries, related primarily to poverty and overcrowding. In remote Aboriginal communities in northern Australia, prevalences of up to 50% among children have been described, despite the availability of effective chemotherapy. Sarcoptic mange is also an important veterinary disease engendering significant morbidity and mortality in wild, domestic, and farmed animals. Scabies is caused by the ectoparasitic mite Sarcoptes scabiei burrowing into the host epidermis. Clinical symptoms include intensely itchy lesions that often are a precursor to secondary bacterial pyoderma, septicemia, and, in humans, poststreptococcal glomerulonephritis. Although diagnosed scabies cases can be successfully treated, the rash of the primary infestation takes 4 to 6 weeks to develop, and thus, transmission to others often occurs prior to therapy. In humans, the symptoms of scabies infestations can mimic other dermatological skin diseases, and traditional tests to diagnose scabies are less than 50% accurate. To aid early identification of disease and thus treatment, a simple, cheap, sensitive, and specific test for routine diagnosis of active scabies is essential. Recent developments leading to the expression and purification of S. scabiei recombinant antigens have identified a number of molecules with diagnostic potential, and current studies include the investigation and assessment of the accuracy of these recombinant proteins in identifying antibodies in individuals with active scabies and in differentiating those with past exposure. Early identification of disease will enable selective treatment of those affected, reduce transmission and the requirement for mass treatment, limit the potential for escalating mite resistance, and provide another means of controlling scabies in populations in areas of endemicity.

Scabies: a ubiquitous neglected skin disease

Scabies has been a scourge among human beings for thousands of years. Its worldwide occurrence with epidemics during war, famine, and overcrowding is responsible for an estimated 300 million people currently infested. Scabies refers to the various skin lesions produced by female mites, and their eggs and scybala that are deposited in the epidermis, leading to delayed-type hypersensitivity reaction. Recent immunological findings such as cross-reactivity with house dust mite allergens and an altered T-helper-1/T-helper-2 pattern contribute to a better understanding of the pathomechanism. Furthermore, progress in molecular biology and cloning of relevant antigens could enable the development of a diagnostic ELISA system and candidate vaccines in the near future. Typical and atypical clinical presentations with pruritus as a hallmark of scabies occur in young, pregnant, immunocompromised, and elderly patients and include bullous and crusted (Norwegian) manifestations as well as those masked by steroid use (scabies incognito). This article reviews scabies management strategies in developed countries and resource-poor communities as well as typical complications, including the emergence of resistance and drug-related adverse events. Other problems such as post-scabies eczema and reinfestation, and newer treatments such as ivermectin are also discussed.

Immunoblot analysis of IgG antibody response to Sarcoptes scabiei in swine

This study was performed to determine the frequencies and specificities of IgG antibodies binding to component of Sarcoptes scabiei extracts in swine with hypersensitive and chronic mange. The hypersensitive form is characterised by pruritus and the presence of small red papules over the flanks and belly. The chronic form is characterised by crusts, which contain large numbers of mites and are attached to the skin; the lesions are most commonly found on the internal pinna extending into the auditory canal. S. scabiei mite extract was separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with subsequent immunoblotting. IgG-binding proteins were detected with individual sera from 30 hypersensitive and 21 chronically infected pigs; eight "Specific Pathogen Free" pigs were used as negative controls. Seven protein bands with molecular weights ranging from >220 to 30 Kilodalton (KDD) (>220, 218, 110, 80, 66, 52, 36 KDD) strongly bound with IgG antibodies; five out of these seven components (218, 110, 80, 66, 52 KDD) bound also with sera from negative pigs. There is a statistically significant difference in the antigenic recognition spectra between hypersensitive and chronically infected pigs; component of >220 KDD is more frequently recognized by chronically infected pigs (P=0.0006, chi(2)=11.74), in contrast component of 36 KDD is more frequently recognized by hypersensitive pigs (P=0.001, chi(2)=10). Our results clearly indicate there is a difference in the reactivity to antigenic peptides/proteins of S. scabiei mite between hypersensitive and chronically infected pigs, and revealed that only two antigens may be considered S. scabiei-specific and used for diagnostic purposes in swine.

Scabies

Scabies is a neglected parasitic disease that is a major public health problem in many resource-poor regions. It causes substantial morbidity from secondary infections and post-infective complications such as acute post-streptococcal glomerulonephritis. Disease control requires treatment of the affected individual and all people they have been in contact with, but is often hampered by inappropriate or delayed diagnosis, poor treatment compliance, and improper use of topical compounds such as permethrin, lindane, or benzyl benzoate. In addition to concerns over toxicity with such compounds, parasite resistance seems to be increasing. Oral ivermectin is an alternative that has been used successfully in community control programmes. Plant derivatives such as turmeric, neem, and tea tree oil are also promising future treatments. The disease is strongly associated with poverty and overcrowding, and the associated stigma can ostracise affected individuals. Treatment of scabies in poor countries needs to integrate drug treatment programmes with efforts to improve the socioeconomic conditions and education programmes to reduce stigma. We expect the future to bring more sensitive and specific clinical and laboratory-based diagnostic methods, as well as new therapeutic strategies.

Presence of host immunoglobulin in the gut of Sarcoptes scabiei (Acari: Sarcoptidae)

Sarcoptes scabiei (De Geer) mites burrow in the nonliving stratum corneum of the epidermis of their mammalian hosts. These mites ingest extracellular fluid (serum) that seeps into the burrow from the lower vascular dermis. A strong host antibody response occurs when mites die in the skin. This suggests internal immunogenic proteins are released into the host at this time. Vaccination with internal antigens may be an approach to protect against this mite if host antibody to internal antigens that regulate key physiological processes is ingested along with serum. Our study clearly showed that scabies mites ingest host immunoglobulin as evidenced by the localization of fluorescent-labeled antibody to host immunoglobulin in the anterior midgut and esophagus of fresh mites removed from the host. This is the first study that demonstrates that this nonblood-feeding ectoparasitic mite ingests host antibody while feeding on tissue fluid that seeps into the stratum corneum.

Mite allergens

There is an increasing awareness of the health implications of mite sensitivity, as it is closely related to asthma. Mite allergy constitutes a complex worldwide problem, with sanitary and economical implications. Not only are mite species present in house dust, producing potent allergens, but other, less studied species are also responsible for significant allergic reactions in occupational settings. In this review, we focus on the growing number of mite species that are implicated in allergic cutaneous and respiratory diseases in humans. Mite allergy is not restricted only to the human "indoor" environment, because numerous reports clearly demonstrate that many species that can induce sensitization and symptoms are encountered in occupational settings. An important component of allergy research is the evaluation of the allergenic cross-reactivity to verify to what extent different mite species have unique, species-specific, or cross-reactive allergens. The results of these investigations have important clinical consequences for the diagnosis and treatment of allergic diseases. Internationally standardized mite extracts are needed to compare sensitization rates around the world and clearly establish risk factors associated with sensitization and asthma. In spite of recent controversial results, a significant reduction in the exposure to mite allergens continues to be an important challenge and one of the main goals in the treatment of mite-induced respiratory symptoms. In many cases, this reduction must be achieved in the workplace as well as in the home environment.

Ectoparasitic infestations

Ectoparasitic infestations are highly prevalent in resource-poor populations throughout the world and are associated with considerable morbidity. Reliable data on the epidemiology, immunology, and therapy of ectoparasitic infestations and on the biology of the parasites remain scarce. The control of parasitic skin diseases, such as scabies, pediculosis, tungiasis, myiasis, and cutaneous larva migrans in endemic areas remains a challenge. Using appropriate study designs, it is imperative to increase further the knowledge on the various aspects of the parasites and the infestations they cause.

Crossreacting IgG antibodies against fox mite antigens in human scabies

Scabies continues to be an important parasitic disease of mammals. There remain, however, major gaps in the understanding of the human host immune response, and a simple diagnostic test is lacking. In contrast to human mites, red fox mites (Sarcoptes scabiei var. vulpis) can be collected easily and have been used, due to crossreactivity, for enzyme-linked immunosorbent assay (ELISA) studies in dogs and pigs. We wanted to investigate the possibility that crossreactivity might also exist for the human mite, and determined titers against fox mite antigens by ELISA in 41 patients with scabies. Specific IgG was significantly higher in patients with scabies than in healthy controls (P=0.01). The sensitivity was, however, only 48%, although it increased slightly during treatment (P=0.86). A positive correlation was also noted between disease duration and severity of infestation (r=0.5), with specific IgG titers increasing in parallel with severity of symptoms (P=0.01). Patients with symptomatic scabies for more than 4 weeks had furthermore significantly higher IgG titers than patients with a shorter duration of disease (P=0.007). In conclusion, these findings demonstrate IgG antibodies in human scabies that crossreact with fox mite antigens, thus encouraging the search for improved ELISAs with more specific mite antigens to produce a more sensitive detection system for scabies in humans.

Skewed Th1/Th2 immune response to Sarcoptes scabiei

Scabies is a contagious skin disease of humans and many other species of mammals. Previous studies suggested that the balance between the Th1 and Th2 immune responses may influence the outcome of a scabies infestation in a sensitized host. Therefore, in this study, we examined the T-helper cell cytokine profiles of splenocytes and lymph node cells in BALB/c mice that were immunized with scabies extract (primary response), infested with scabies mites (primary response), or immunized and then infested (secondary response). Lymphocyte cytokine expression was analyzed by flow cytometry after staining for intracellular cytokines. Immunization with scabies extract induced production of interferon-gamma (IFNgamma) (Th1 response) by both spleen and lymph node cells. Mice that were infested with scabies increased production of interleukin-4 by lymph node cells and of IFNgamma by splenocytes. Mice that were first immunized and then infested with mites increased production of IFNgamma by both spleen and lymph node cells. However, this increased level of IFNgamma was only about half of that induced by immunization alone. These results suggest that live scabies mites produced something that inhibited IFNgamma production in the lymph nodes of scabies-immunized mice. Our data also indicate that lymphocytes in the spleen and lymph nodes can present different cytokine response profiles.

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.