Sarcoptes scabiei: genomics to proteomics to biology

Can Ivermectin kill Sarcoptes scabiei during the molting process?

BACKGROUND

Sarcoptes scabiei is a permanent obligate ectoparasite that lives and reproduces in the epidermis of humans and other mammals worldwide. There is a lack of information on the molting process of Sarcoptes scabiei. Ivermectin is widely used to treat Sarcoptes infection in humans and animals, while the survival of molting Sarcoptes mites in the presence of ivermectin is unknown. The aim of the present study is to investigate the molting process of Sarcoptes mites and assess the activity of ivermectin during the molting process of Sarcoptes mites.

METHODOLOGY/PRINCIPAL FINDINGS

molting Sarcoptes mites were incubated at 35°C and 80% relative humidity and observed hourly until complete molt. Of the 192 molting mites recorded, the longest molt periods for larvae and nymphs were 23 and 30 h, respectively. The activity of ivermectin on molting Sarcoptes mites was also assessed using two concentrations of the drug (0.1 and 0.05 mg/ml). The exposure time for molting mites was determined by 100% mortality of female mites exposed to the solution of ivermectin. While all female mites were killed after exposure to 0.1 mg/ml ivermectin for 2 h and and 0.05 mg/ml for 7 h, 32% and 36% of molting mites survived and successfully molted, respectively.

CONCLUSIONS/SIGNIFICANCE

The present study demonstrated that molting Sarcoptes mites are less susceptible to ivermectin than active mites. As a consequence, mites may survive after two doses of ivermectin given 7 days apart due not only to hatching eggs but also to the resistance of mites during their molting process. Our results provide insight into the optimal therapeutic regimens for scabies and highlight the need for further research on the molting process of Sarcoptes mites.

Identification and genetic characterisatin of cathepsin L in Demodex

Owing to difficulties in obtaining functional gene sequences, molecular pathogenic mechanisms in Demodex have been understudied. In this study, overlap extension PCR was used to obtain the sequences of cathepsin L (CatL), a pathogenicity-related gene, to provide a foundation for subsequent functional research. Demodex folliculorum and Demodex brevis mites were obtained from the face skin of Chinese individuals, and Demodex canis mites were isolated from the skin lesions of a dog. RNA was extracted and used to synthesise double-stranded cDNA. PCR amplification, cloning, sequencing, and bioinformatics analysis of CatL were performed. CatL gene sequences of 1005, 1008, and 1008 bp were successfully amplified for D. brevis, D. folliculorum, and D. canis, respectively. These sequences showed 99.9 or 100% identity with templates previously obtained by RNA-seq. The Maximum Likelihood (ML) phylogenetic tree showed that D. folliculorum clustered with D. canis first, then with D. brevis, and finally with other Acariformes mite species. The three Demodex species had nine similar motifs to those of Sarcoptes scabies, Dermatophagoides pteronyssinus, and Dermatophagoides farinae, and motifs 10-13 were valuable for identification. CatL proteins of Demodex species were predicted to be approximately 38 kDa, be located in lysosomes, have a signal peptide but no transmembrane region, and have two functional domains, I29 and Pept_C1. However, interspecific differences were observed in secondary and tertiary protein structures. In conclusion, we successfully obtained CatL sequences of three Demodex species by overlap extension PCR, which creates conditions for further pathogenic mechanism studies.

Dermoscopic features of children scabies

Scabies is a common skin disorder, caused by the ectoparasite Sarcoptes scabiei. The scabies mites burrow is highly diagnostic but illegible by the naked eye, because it is tiny and may completely be obscured by scratch and crust. The classic technique is opening the end of an intact mite burrow with a sharp instrument and inspecting its contents in the light microscope under loupe vision. Dermatoscope is a new method to diagnose scabies, with the advantages of non-invasive and more sensitive. This study verified the characteristic manifestations of scabies under dermoscopy. Under the closer examination of the curvilinear scaly burrow, the scabies mite itself may be seen as a dark equilateral triangular structure, which is often referred to as a "jet with contrail." Besides, this study found that the positive detection rate of microscopic characteristic manifestations under the dermoscopy ordered by the external genitals, the finger seams and the trunk, which were statistically different (P-value < 0.05). Of note, this is the first study to explore the regional distribution of the characteristic dermoscopic manifestations of scabies. We are the first to propose to focus on examining the external genitalia and finger seams with dermoscopy.

Assembly of a Draft Genome for the Mouse Ectoparasite Myocoptes musculinus

Myocoptes musculinus is a common ectoparasite of wild mice and is occasionally found on research mice. Infestations of research mice are often subclinical but can cause severe dermatitis. Perhaps more importantly, infestations can cause immunologic reactions that may alter research outcomes, and most animal research facilities strive to prevent or eliminate mites from their mouse colonies. M. musculinus infestations are currently detected by using microscopic evaluation of the fur and skin and PCR assays of pelt swabs targeting the rRNA genes of this mite. In our facility, we encountered multiple, false-positive 18S rRNA PCR results from a closed mouse colony. We could not identify the source of the false positives even after performing PCR analysis of other Myocoptes gene targets using assays developed from the few other target genomic sequences available for M. musculinus or Myocoptes japonensis in public databases. This situation highlighted the limited genetic resources available for development of diagnostic tests specific for this ectoparasite. To expand the available genetic resources, we generated a metagenome of M. musculinus derived by sequencing from fur plucks of an infected mouse. We also determined the completeness of this metagenome and compared it with those of related mites.

Proteomic analysis of Sarcoptes scabiei reveals that proteins differentially expressed between eggs and female adult stages are involved predominantly in genetic information processing, metabolism and/or host-parasite interactions

Presently, there is a dearth of proteomic data for parasitic mites and their relationship with the host animals. Here, using a high throughput LC-MS/MS-based approach, we undertook the first comprehensive, large-scale proteomic investigation of egg and adult female stages of the scabies mite, Sarcoptes scabiei-one of the most important parasitic mites of humans and other animals worldwide. In total, 1,761 S. scabiei proteins were identified and quantified with high confidence. Bioinformatic analyses revealed differentially expressed proteins to be involved predominantly in biological pathways or processes including genetic information processing, energy (oxidative phosphorylation), nucleotide, amino acid, carbohydrate and/or lipid metabolism, and some adaptive processes. Selected, constitutively and highly expressed proteins, such as peptidases, scabies mite inactivated protease paralogues (SMIPPs) and muscle proteins (myosin and troponin), are proposed to be involved in key biological processes within S. scabiei, host-parasite interactions and/or the pathogenesis of scabies. These proteomic data will enable future molecular, biochemical and physiological investigations of early developmental stages of S. scabiei and the discovery of novel interventions, targeting the egg stage, given its non-susceptibility to acaricides currently approved for the treatment of scabies in humans.

Immunomodulatory effects of two recombinant arginine kinases in Sarcoptes Scabiei on host peripheral blood mononuclear cells

Background

As an important zoonotic parasitic disease with global distribution, scabies causes serious public health and economic problems. Arginine kinase (AK) is involved in cell signal transduction, inflammation, and apoptosis. Two AKs were identified in Sarcoptes scabiei, but their functions in the host immune response remain unclear.

Methods

rSsAK-1 and rSsAK-2 were expressed, purified, and immunolocalized. The effects of rSsAK-1 and rSsAK-2 on rabbit PBMC proliferation, apoptosis, and migration; Bcl-2, Bcl-xl, Fas, Bax, and NF-κB transcription levels; and IL-2, IFN-γ, IL-4, IL-10, TGF-β1, and IL-17 secretion were detected.

Results

rSsAK-1 and rSsAK-2 were cloned and expressed successfully. Both enzymes were ~57 kDa and contained 17-kDa tagged proteins, and had good catalytic activity and immunoreactivity. The proteins were located in the S. scabiei exoskeleton, chewing mouthparts, legs, stomach, and intestine. SsAK-1 and SsAK-2 were secreted in the pool and epidermis of the skin lesions, which may be involved in S. scabiei–host interaction. rSsAK-1 and rSsAK-2 significantly promoted cell proliferation, induced cell migration, inhibited apoptosis, and increased Bcl-2, Bcl-xl and NF-κB (p65) transcription levels concentration-dependently, and inhibited IL-2, IFN-γ, and IL-10 secretion and promoted IL-4 and IL-17 secretion.

Conclusion

rSsAK-1 and rSsAK-2 might increase Bcl-2 and Bcl-xl expression by activating the NF-κB signaling pathway to promote cell proliferation and inhibit apoptosis, which induced PBMC survival. By inducing PBMC migration to the infection site, rSsAK-1 and rSsAK-2 shifted the Th1/Th2 balance toward Th2 and changed the Th17/Treg balance, which indicated their immune role in S. scabiei allergic inflammation.

Characterization of tick salivary gland and saliva alphagalactome reveals candidate alpha-gal syndrome disease biomarkers

BACKGROUND

Ticks are obligate hematophagous arthropods that synthesize the glycan Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal) associated with the alpha-gal syndrome (AGS) or allergy to mammalian meat consumption.

RESEARCH DESIGN AND METHODS

In this study, we used a proteomics approach to characterize tick proteins in salivary glands (sialome SG), secreted saliva (sialome SA) and with α-Gal modification (alphagalactome SG and SA) in model tick species associated with the AGS in the United States (Amblyomma americanum) and Australia (Ixodes holocyclus). Selected proteins reactive to sera (IgE) from patients with AGS were identified to advance in the identification of possible proteins associated with the AGS. For comparative analysis, the α-Gal content was measured in various tick species.

RESULTS

The results confirmed that ticks produce proteins with α-Gal modifications and secreted into saliva during feeding. Proteins identified in tick alphagalactome SA by sera from patients with severe AGS symptomatology may constitute candidate disease biomarkers.

CONCLUSIONS

The results support the presence tick-derived proteins with α-Gal modifications in the saliva with potential implications in AGS and other disorders and protective capacity against tick infestations and pathogen infection. Future research should focus on the characterization of the function of tick glycoproteins with α-Gal in tick biology and AGS.

Sarcoptic mange: An emerging panzootic in wildlife

Sarcoptic mange, a skin infestation caused by the mite Sarcoptes scabiei, is an emerging disease for some species of wildlife, potentially jeopardizing their welfare and conservation. Sarcoptes scabiei has a near-global distribution facilitated by its forms of transmission and use of a large diversity of host species (many of those with broad geographic distribution). In this review, we synthesize the current knowledge concerning the geographic and host taxonomic distribution of mange in wildlife, the epidemiological connections between species, and the potential threat of sarcoptic mange for wildlife conservation. Recent sarcoptic mange outbreaks in wildlife appear to demonstrate ongoing geographic spread, increase in the number of hosts and increased virulence. Sarcoptic mange has been reported in at least 12 orders, 39 families and 148 species of domestic and wild mammals, making it one of the most generalist ectoparasites of mammals. Taxonomically, the orders with most species found infested so far include Perissodactyla (67% species from the entire order), Artiodactyla (47%), and Diprotodontia (67% from this order). This suggests that new species from these mammal orders are likely to suffer cross-species transmission and be reported positive to sarcoptic mange as surveillance improves. We propose a new agenda for the study of sarcoptic mange in wildlife, including the study of the global phylogeography of S. scabiei, linkages between ecological host traits and sarcoptic mange susceptibility, immunology of individuals and species, development of control strategies in wildlife outbreaks and the effects of global environmental change in the sarcoptic mange system. The ongoing transmission globally and sustained spread among areas and wildlife species make sarcoptic mange an emerging panzootic in wildlife. A better understanding of sarcoptic mange could illuminate the aspects of ecological and evolutionary drivers in cross-species transmission for many emerging diseases.

Efficacy of afoxolaner plus milbemycin oxime and afoxolaner alone as treatment for sarcoptic mange in naturally infested dogs

Sarcoptic mange is a pruritic, contagious, ectoparasitic skin disease that affects mammals, including the domestic dog. The objective of this study was to evaluate and compare the efficacy of afoxolaner plus milbemycin oxime (NexGard Spectra) and afoxolaner alone (NexGard) as treatments for sarcoptic mange in naturally infested dogs. A total of 142 dogs naturally infested with Sarcoptes scabiei was evaluated. The dogs were diagnosed by microscopic examinations of skin scrapings. The dogs were divided into 2 groups: 96 dogs were treated with a combined dosage of 2.50 to 5.36 mg/kg body weight (BW) of afoxolaner and 0.50 to 1.07 mg/kg BW of milbemycin oxime and 46 dogs were treated with 2.50 mg/kg BW of afoxolaner alone. The presence or absence of pruritus and lesions were evaluated using an analogous scale on days 7, 14, 21, 28, and 56 after receiving the treatment. Data obtained were analyzed by Student's t-test (P ≤ 0.05). The single oral treatment of afoxolaner plus milbemycin oxime resulted in a significant reduction in pruritus of 87.4% at 28 d after treatment (P ≤ 0.05). Resolution of the lesions after treatment was variable, with a significant decrease (P ≤ 0.05) observed within the first 14 d, although this parameter continued to improve until the end of the study on day 28, when a decrease of 96% was observed. By the end of the study, a single dose of either the afoxolaner alone or the afoxolaner combined with milbemycin oxime was effective in significantly reducing the signs associated with sarcoptic mange during a 56-day evaluation period.

Genital scabies: Haven of an unwelcome guest

The itch mite Sarcoptes scabiei var. hominis has been a menace to humanity for ages. Diagnosing scabies can be a challenge in view of the varied presentations of the disease. The male genitalia are an important area of predilection of the mite. Examination of this often overlooked area is essential as it may reveal both characteristic and atypical manifestations of scabies. Genital involvement also attains special relevance in view of the possible sexual transmission of the mite. In addition to the morbidity caused by itching, patients may have to deal with myths, stigma, and embarrassment.

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.

Phylogenetic relationships, stage-specific expression and localisation of a unique family of inactive cysteine proteases in Sarcoptes scabiei

Background

Scabies is worldwide one of the most common, yet neglected, parasitic skin infections, affecting a wide range of mammals including humans. Limited treatment options and evidence of emerging mite resistance against the currently used drugs drive our research to explore new therapeutic candidates. Previously, we discovered a multicopy family of genes encoding cysteine proteases with their catalytic sites inactivated by mutation (SMIPP-Cs). This protein family is unique in parasitic scabies mites and is absent in related non-burrowing mites. We postulated that the SMIPP-Cs have evolved as an adaptation to the parasitic lifestyle of the scabies mite. To formulate testable hypotheses for their functions and to propose possible strategies for translational research we investigated whether the SMIPP-Cs are common to all scabies mite varieties and where within the mite body as well as when throughout the parasitic life-cycle they are expressed.

Results

SMIPP-C sequences from human, pig and dog mites were analysed bioinformatically and the phylogenetic relationships between the SMIPP-C multi-copy gene families of human, pig and dog mites were established. Results suggest that amplification of the SMIPP-C genes occurred in a common ancestor and individual genes evolved independently in the different mite varieties. Recombinant human mite SMIPP-C proteins were produced and used for murine polyclonal antibody production. Immunohistology on skin sections from human patients localised the SMIPP-Cs in the mite gut and in mite faeces within in the epidermal skin burrows. SMIPP-C transcription into mRNA in different life stages was assessed in human and pig mites by reverse transcription followed by droplet digital PCR (ddPCR). High transcription levels of SMIPP-C genes were detected in the adult female life stage in comparison to all other life stages.

Conclusions

The fact that the SMIPP-Cs are unique to three Sarcoptes varieties, present in all burrowing life stages and highly expressed in the digestive system of the infective adult female life stage may highlight an essential role in parasitism. As they are excreted from the gut in scybala they presumably are able to interact or interfere with host proteins present in the epidermis.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2862-0) contains supplementary material, which is available to authorized users.

MOLECULAR IDENTIFICATION OF SARCOPTES SCABIEI VAR. CUNICULI FROM SURABAYA AND MALANG REGIONS OF EAST JAVA

Scabies is a zoonotic skin disease caused by Sarcoptes scabiei mites. As an emerging/re-emerging parasitic disease, scabies represents a significant global threat to both human and animal health. Numerous cases of scabies in Indonesia have been reported, which support research on the prevalence of S. scabiei. However, most such studies have involved conventional morphological studies, with limited molecular diagnostic studies. The purpose of the present study was the genetic characterization of S. scabiei var. cuniculi in domestic rabbits to generate baseline genotypic data. S. scabiei var. cuniculi was isolated and identified from scabies-infected rabbits from the Surabaya and Malang regions of East Java. Molecular identification was performed using Polymerase Chain Reaction (PCR) using specific primers targeting the COX1 gene. We performed COX1 PCR using rabbit isolates of S. scabiei from Indonesia. To the best of our knowledge, no such study had been reported previously. This study was performed in the Laboratory of Veterinary Parasitology, Faculty of Veterinary Medicine and the Tropical Disease Diagnostic Center Laboratory, Universitas Airlangga. The results with agarose gel electrophoresis revealed a 289 bp PCR product amplified from the DNA of S. scabiei isolates from both Surabaya and Malang in accordance with the expected COX1 amplicon size, that indicated a single band 289 bp in length, demonstrating specific detection of S. scabiei var. cuniculi from Surabaya and Malang using COX1 primers. The results were consistent with the calculated amplicon size based on primer positions within the COX1 locus, with the forward primer spanning nucleotides 61–94, and the reverse primer spanning nucleotides 331–350 ( 350 − 61 = 289 bp).  PCR genotyping of the isolates yielded an identical nucleotide length of 289 bp. Further studies are required to sequence the amplified fragments for homology assessment.

Molecular characteristics and serodiagnostic potential of chitinase-like protein from Sarcoptes scabiei

Scabies, caused by the mite Sarcoptes scabiei, is an allergic skin disease that affects millions of people and other mammals worldwide. This highly contagious parasitic disease is among the top 50 epidemic disease and is regarded as a neglected tropical disease. Diagnosis of scabies is difficult in the early stage, and the pathogenesis of scabies is not currently clear. Here, we expressed, identified and located the chitinase-like protein of S. scabiei (SsCLP), and evaluated its potential as an early-stage diagnostic antigen for rabbit scabies. Indirect ELISA using recombinant SsCLP (rSsCLP) exhibited diagnostic sensitivity of 94.4% (17/18) and specificity of 86.7% (26/30). Early diagnostic test after artificial infection of rabbits with S. scabiei for 1 week showed a positive detection rate of 96.7% (29/30). Immunolocalization assays showed that fluorescence signals were localized on the surface of mites and, in infected rabbits, were observed in keratinized skin and embedded mites. Intradermal skin tests of rabbits by injecting rSsCLP showed a wheal, flare and erythema reaction. These results suggest that S. scabiei chitinase-like protein is conducive to host invasion, participates in inducing the allergic response of the host, and is an effective antigen for the diagnosis of S. scabiei.

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.

Proteases of Dermatophagoides pteronyssinus

Since the discovery that Der p 1 is a cysteine protease, the role of proteolytic activity in allergic sensitization has been explored. There are many allergens with proteolytic activity; however, exposure from dust mites is not limited to allergens. In this paper, genomic, transcriptomic and proteomic data on Dermatophagoides pteronyssinus (DP) was mined for information regarding the complete degradome of this house dust mite. D. pteronyssinus has more proteases than the closely related Acari, Dermatophagoides farinae (DF) and Sarcoptes scabiei (SS). The group of proteases in D. pteronyssinus is found to be more highly transcribed than the norm for this species. The distribution of protease types is dominated by the cysteine proteases like Der p 1 that account for about half of protease transcription by abundance, and Der p 1 in particular accounts for 22% of the total protease transcripts. In an analysis of protease stability, the group of allergens (Der p 1, Der p 3, Der p 6, and Der p 9) is found to be more stable than the mean. It is also statistically demonstrated that the protease allergens are simultaneously more highly expressed and more stable than the group of D. pteronyssinus proteases being examined, consistent with common assumptions about allergens in general. There are several significant non-allergen outliers from the normal group of proteases with high expression and high stability that should be examined for IgE binding. This paper compiles the first holistic picture of the D. pteronyssinus degradome to which humans may be exposed.