Immunoblot analysis of IgG antibody response to Sarcoptes scabiei in swine

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.

Porcine scabies induces marked apoptosis, increased pro-inflammatory cytokines IL-1, TNF-α and shedding of ICAM-1

BACKGROUND

Scabies is one of the leading causes of morbidity in pigs worldwide. Limited data are available regarding the role of immune reactions in the development of porcine scabies.

MATERIALS AND METHODS

The aim of this study was to investigate key pro-inflammatory cytokines (IL-1, TNF-α), soluble variant of adhesion molecule ICAM-1 and mite-mediated apoptosis of peripheral leukocytes in 20 pigs with scabies, in addition to 10 healthy controls. The pigs with at least three typical clinical signs and found positive for Sarcoptes scabiei var. suis in microscopy were recruited for the present study.

RESULTS

IL-1 acted as the major pro-inflammatory cytokine as serum IL-1 concentrations showed significantly (p < .05) higher levels (7-fold increase) in cases than in controls. The minor cytokine TNF-α was 4-fold higher during scabies, and its mean serum concentration was significantly increased (p < .05) in cases when compared to healthy controls. Soluble ICAM-1 levels were significantly higher (p < .05) in all the pigs of infested group compared with the controls. The percentage of apoptotic and necrotic leukocytes was found to be significantly higher (p < .05) in scabies positive pigs as compared to the healthy controls.

CONCLUSION

It is concluded that systemic elevation in pro-inflammatory cytokines IL-1 and TNF-α, shedding of soluble ICAM-1 variant in peripheral blood and increased rate of host-cell apoptosis in peripheral leukocytes might be implicated in the immunopathology of naturally acquired porcine scabies.

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.

Sarcoptic mange infestation in pigs: an overview

Sarcoptic mange infestation in pigs is caused by Sarcoptes scabiei var. suis. It is the most common mange infestation of pigs. The parasite is distributed worldwide. Pig owners are generally concerned about the internal parasitic infections and ignored the external parasitic infestations. But the external parasitic infestation with S. scabiei var. suis has economic significance as it causes morbidity, mortality, decreased fertility and feed conversion ratio in pigs. Keeping in view of importance of S. scabies var. suis infestation in pigs, this communication discussed about the present and past research works done on S. scabies var. suis infestation in pigs, particularly its prevalence, life cycle, pathological lesions, clinical symptoms, haematobiochemical changes, diagnosis, treatment and control, to have an idea about this infestation at a glance. It has been concluded that the research work done on sarcoptic mange infestation in pigs in India is less in comparison to other countries. It may be due to its consideration as a neglected parasite or due to it's under report. Organization of awareness programs for the farmers by extension personalities or other authorities might be able to save the farmers from economic losses due to this infestation.

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.

Variable performance of a human derived Sarcoptes scabiei recombinant antigen ELISA in swine mange diagnosis

The performance of an indirect ELISA test based on Sarcoptes scabiei var hominis recombinant antigen Ssλ20ΔB3 (rec-ELISA), to diagnose pig mange was investigated in 15 experimentally infected and non-infected pigs and 692 commercial pigs from 16 herds in southeast Spain. These latter animals included 6-7 month old fatteners (13 herds), 11-12 month old replacement sows (1 herd) and ≥24 month old breeding sows (7 herds). All pigs were examined for mites in ear skin scrapings and the presence of S. scabiei-associated macroscopic dermatitis; moreover, fatteners were also tested for antibodies against porcine viruses including: Aujeszky disease virus (ADV), swine influenza virus (SIV), type 2 porcine circovirus (PCV2) and porcine respiratory and reproductive syndrome virus (PRRSV). S. scabiei and chronic hyperkeratotic dermatitis were detected in breeding sows from 6 herds. Mite prevalence in other pigs was 83% in replacement sows, 0% in 7 fattener's herds and 3-82% in other fattener's herds. All fattener herds had pigs with acute hypersensitivity dermatitis and the percentage of affected pigs and lesion area was significantly greater in S. scabiei infected ones. Rec-ELISA relative optical densities (RODs) were greater in older than in young pigs, as well as in infected compared to non-infected pigs. However, RODs differed significantly between infected individuals, regardless of age and origin (commercial or experimental) and the herd prevalence of S. scabiei. Low repeatability between ELISA microtiter plates, suggesting variable specific antibody binding to antigen, are likely partly responsible for ROD variation. Other potential causes of variation were examined in fatteners using random effects logistic regression analysis, after defining a seropositivity threshold value with receiver-operating characteristics (ROC) analysis. The logistic model indicated that seropositivity was associated with large dermatitis areas and with the only herd with low PCV2 seroprevalence. Pigs with more extensive dermatitis may have older infections and more rec-ELISA detectable antibodies. The possibility that PCV2, a recognized immunosupressor, depresses antibody production against S. scabiei infection merits further attention. In summary, results indicate some potential of the studied rec-ELISA as a complementary tool for herd-level swine mange diagnosis, and that work to reduce internal and external sources of assay variation is essential.

Characterisation of Sarcoptes scabiei antigens

In pig herds, the status of Sarcoptes scabiei infections is routinely monitored by serodiagnosis. Crude antigen for ELISA is usually prepared from S. scabiei var. canis or other variations and may lead to variations in the outcome of different tests, making assay standardisation difficult. This study was performed to investigate the antigen profiles of S. scabiei, including differences between hydrophilic and more hydrophobic protein fractions, by Western blotting with sera from pigs with defined infection status. Potential cross-reactivity among S. scabiei (var. canis, suis and bovis), Dermatophagoides farinae and Tyrophagus putrescentiae was also analysed. Hydrophobic S. scabiei antigens were detectable in the range of 40-50 kDa, whilst the hydrophilic fraction showed no specific antigenicity. In the hydrophobic fractions of D. farinae and T. putrescentiae, two major protein fractions in a similar size range could be identified, but no cross-reactivity with Sarcoptes-positive sera was detectable. However, examination of the hydrophilic fractions revealed cross-reactivity between Sarcoptes-positive sera and both the house dust mite and the storage mite in the range of 115 and 28/38 kDa. Specific bands in the same range (42 and 48 kDa) could be detected in blots from hydrophobic fractions of all three tested variations of S. scabiei (var. canis, bovis and suis). These results show that there are considerable differences in mange antibody reactivity, including reactions with proteins from free-living mites, which may interfere with tests based on hydrophilic antigens. Further refinement of antigen and the use of specific hydrophobic proteins could improve ELISA performance and standardisation.

A tractable experimental model for study of human and animal scabies

BACKGROUND

Scabies is a parasitic skin infestation caused by the burrowing mite Sarcoptes scabiei. It is common worldwide and spreads rapidly under crowded conditions, such as those found in socially disadvantaged communities of Indigenous populations and in developing countries. Pruritic scabies lesions facilitate opportunistic bacterial infections, particularly Group A streptococci. Streptococcal infections cause significant sequelae and the increased community streptococcal burden has led to extreme levels of acute rheumatic fever and rheumatic heart disease in Australia's Indigenous communities. In addition, emerging resistance to currently available therapeutics emphasizes the need to identify potential targets for novel chemotherapeutic and/or immunological intervention. Scabies research has been severely limited by the availability of parasites, and scabies remains a truly neglected infectious disease. We report development of a tractable model for scabies in the pig, Sus domestica.

METHODOLOGY/PRINCIPAL FINDINGS

Over five years and involving ten independent cohorts, we have developed a protocol for continuous passage of Sarcoptes scabiei var. suis. To increase intensity and duration of infestation without generating animal welfare issues we have optimised an immunosuppression regimen utilising daily oral treatment with 0.2 mg/kg dexamethasone. Only mild, controlled side effects are observed, and mange infection can be maintained indefinitely providing large mite numbers (> 6000 mites/g skin) for molecular-based research on scabies. In pilot experiments we explore whether any adaptation of the mite population is reflected in genetic changes. Phylogenetic analysis was performed comparing sets of genetic data obtained from pig mites collected from naturally infected pigs with data from pig mites collected from the most recent cohort.

CONCLUSIONS/SIGNIFICANCE

A reliable pig/scabies animal model will facilitate in vivo studies on host immune responses to scabies including the relations to the associated bacterial pathogenesis and more detailed studies of molecular evolution and host adaptation. It is a most needed tool for the further investigation of this important and widespread parasitic disease.

Sarcoptic mange infestation in pigs in a hilly region of Meghalaya

Skin lesions were collected from 15 adult crossbred pigs maintained at the pig farm of ICAR Research Complex for the North-Eastern Hill Region, Umiam, a hilly region of the state of Meghalaya, India. Skin scrapings of these 15 animals were examined by KOH digestion method. Presence of mites were detected in five animals which were indistinguishable from Sarcoptes scabiei var. suis. Infected pigs were treated with a single dose of Ivermectin at 200 ug/kg body weight, subcutaneously. No mites were recovered from treated pigs after a period of 10 days of post-treatment. The presence of S. scabiei var. suis in pigs from this part of the country has never been reported. This infestation has great significance because it affects the growth rate and feed conversion significantly, specially to the grower and weaned pigs. It can be concluded that S. scabiei var. suis infestation is prevalent in hilly region of Meghalaya. The pig producers are generally unaware about the severity of the problem of mite infestation, so precaution should be taken to prevent their valuable pigs from S. scabiei var. suis infestation.