Two simple techniques for the safe Sarcoptes collection and individual mite DNA extraction

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.

First description of sarcoptic mange in an Iberian hare (Lepus granatensis)

The Iberian hare (Lepus granatensis) is a popular small game species in the Iberian Peninsula, and it has never been reported to be affected by sarcoptic mange. An adult female Iberian hare with overt skin lesions on forelimbs and ventral thorax, suggestive of sarcoptic mange, was culled in Quart de les Valls municipality in the Valencian Community, Spain, in 2019. Skin scrapings were digested in 10% KOH solutions to confirm the presence of mites. Ten Sarcoptes microsatellite markers were used to characterize the genetic structure of mites obtained from the hare, and from sympatric and allopatric wild rabbits (Oryctolagus cuniculus) and red foxes (Vulpes vulpes). A total of 56 alleles were counted across the 10 microsatellite loci. Six private alleles were found at four loci (Sarms 33, 38, 41, 45). The multivariate analysis characterized three main clusters, corresponding to mites collected on foxes originating from Catalonia, foxes from Valencia and the hare plus wild rabbits. To our knowledge, this is the first reported case of sarcoptic mange in the Iberian hare. The origin was molecularly traced back to contacts with endemically infected wild rabbits. We encourage further investigations on cross-transmissibility of S. scabiei between wild rabbits and the diverse representatives of Lepus spp.

•

Crusted scabies in an Iberian hare was detected for the first time in Valencia, Spain in 2019.

•

Wild rabbits might be a natural source of infection of S. scabiei for the Iberian hare, rather than sympatric predators.

•

Microsatellite markers are efficient epidemiological tools for tracing the source of Sarcoptes scabiei infection.

New techniques to collect live Sarcoptes scabiei and evaluation of methods as alternative diagnostics for infection

Sarcoptes scabiei is a widespread, highly contagious skin disease that affects many mammals including humans. The biological characteristics of S. scabiei remain unclear. Therefore, the ability to collect adequate amount of mites for studies is required to advance our understanding of the parasite. The present study aimed to find a method to collect an adequate amount of live S. scabiei mites within a short time frame. The cornified layer and fur from an infected raccoon dog were inserted into a 50-ml catheter tip-type syringe. A 1.5-ml microtube was attached at the tip of the syringe to collect the mites, which crawled out from the cornified layer and fur. Four conditions were examined, and the following condition was determined to be the best: the syringe and microtube were shaded by aluminum foil, and the microtube was heated using a pet heater (36 °C). In addition, the effectiveness of this method as an alternative method to diagnose S. scabiei infections in animal was evaluated. S. scabiei live mites were not detected in the raccoon dog samples 24 h after the administration of medication (ivermectin or selamectin). The present study revealed that this technique was useful to collect adequate amounts of live mites, and the mites prefer a heated environment and actively move when using the shaded conditions. In addition, this technique was effective as an alternative diagnostic technique to detect live mites on an animal body.

Are humans the initial source of canine mange?

Background

Scabies, or mange as it is called in animals, is an ectoparasitic contagious infestation caused by the mite Sarcoptes scabiei. Sarcoptic mange is an important veterinary disease leading to significant morbidity and mortality in wild and domestic animals. A widely accepted hypothesis, though never substantiated by factual data, suggests that humans were the initial source of the animal contamination. In this study we performed phylogenetic analyses of populations of S. scabiei from humans and from canids to validate or not the hypothesis of a human origin of the mites infecting domestic dogs.

Methods

Mites from dogs and foxes were obtained from three French sites and from other countries. A part of cytochrome c oxidase subunit 1 (cox1) gene was amplified and directly sequenced. Other sequences corresponding to mites from humans, raccoon dogs, foxes, jackal and dogs from various geographical areas were retrieved from GenBank. Phylogenetic analyses were performed using the Otodectes cynotis cox1 sequence as outgroup. Maximum Likelihood and Bayesian Inference analysis approaches were used. To visualize the relationship between the haplotypes, a median joining haplotype network was constructed using Network v4.6 according to host.

Results

Twenty-one haplotypes were observed among mites collected from five different host species, including humans and canids from nine geographical areas. The phylogenetic trees based on Maximum Likelihood and Bayesian Inference analyses showed similar topologies with few differences in node support values. The results were not consistent with a human origin of S. scabiei mites in dogs and, on the contrary, did not exclude the opposite hypothesis of a host switch from dogs to humans.

Conclusions

Phylogenetic relatedness may have an impact in terms of epidemiological control strategy. Our results and other recent studies suggest to re-evaluate the level of transmission between domestic dogs and humans.

Universal conventional and real-time PCR diagnosis tools for Sarcoptes scabiei

BACKGROUND

The mite Sarcoptes scabiei has a known host-range of over 100 mammal species including humans. One of the prime objectives of the Sarcoptes-World Molecular Network (WMN) is to design and develop universal Sarcoptes PCR-based diagnosis methods.

METHODS

We describe here for the first time two universal mitochondrial-based diagnosis methods: (i) conventional end-point PCR and (ii) TaqMan real-time PCR. The design of both of these universal diagnosis methods was based on Sarcoptes samples collected from 23 host species in 14 countries.

RESULTS

These methods, based on skin scrapings, were successfully used to etiologically confirm the diagnosis of different clinical degrees of sarcoptic mange in 48 animals belonging to six species. These universal PCR-based diagnosis methods are highly specific, technically sensitive and simple, and are based on the amplification of 135 bp from the Mitochondrial 16S rDNA. The method based on TaqMan real-time qPCR was more sensitive than the conventional end-point PCR.

CONCLUSIONS

Two universal PCR-based diagnosis methods for S. scabiei were successfully designed and applied; one based on conventional end-point PCR and the other on TaqMan real-time PCR. We recommend further testing and the application of these new universal methods worldwide.

Sarcoptes scabiei mites in humans are distributed into three genetically distinct clades

Scabies is an ectoparasitic infestation caused by the mite Sarcoptes scabiei. Currently, S. scabiei is taxonomically divided into different varieties on the basis of host origin. Genetics-based research on scabies has been conducted, but the data on genetic diversity of populations of this mite in humans in Europe are lacking. We evaluated the genetic diversity of populations of S. scabiei. A large series of mites obtained from humans in France and the data of mites from various hosts and geographical areas retrieved from GenBank were included to investigate whether mites are divided into distinct populations. The study of cytochrome c oxidase subunit 1 gene polymorphisms were found to be best suited for phylogenetic analysis. S. scabiei mites were distributed into three genetically distinct clades, with most mites clustering in clades B and C. The Fst value and the Nm value calculated for mites included in clades B and C indicated a strong population structure and a very low gene flow between mites of those clades. The results of the present study not only support the rejection of the hypothesis of panmixia for S. scabiei in humans but also suggest that mites belonging to different clades are genetically isolated. Moreover, the results suggest that the subdivision of S. scabies in varieties according to animal or human hosts is not warranted. In conclusion, S. scabiei mites in humans do not constitute a homogeneous population. Further investigations are now required to assess whether different clinical forms of scabies are associated with particular haplotypes or clades.

Advances in studies of disease-navigating webs: Sarcoptes scabiei as a case study

The discipline of epidemiology is the study of the patterns, causes and effects of health and disease conditions in defined anima populations. It is the key to evidence-based medicine, which is one of the cornerstones of public health. One of the important facets of epidemiology is disease-navigating webs (disease-NW) through which zoonotic and multi-host parasites in general move from one host to another. Epidemiology in this context includes (i) classical epidemiological approaches based on the statistical analysis of disease prevalence and distribution and, more recently, (ii) genetic approaches with approximations of disease-agent population genetics. Both approaches, classical epidemiology and population genetics, are useful for studying disease-NW. However, both have strengths and weaknesses when applied separately, which, unfortunately, is too often current practice. In this paper, we use Sarcoptes scabiei mite epidemiology as a case study to show how important an integrated approach can be in understanding disease-NW and subsequent disease control.

Molecular survey of knockdown resistance to pyrethroids in human scabies mites

There are growing concerns about the emergence of resistance of Sarcoptes scabiei to permethrin and other pyrethroid derivatives. Sarcoptes scabiei mites collected from 40 patients visiting two hospitals near Paris, France, were genotypically characterized considering two parts of their voltage-sensitive sodium channel gene. No nucleotide polymorphism resulting in a codon change at codon 733 or other positions associated with knockdown resistance in other arthropods has been identified. These data may establish a reference line for future surveys of the susceptibility of S. scabiei in the area.

Complete sequence analysis of 18S rDNA based on genomic DNA extraction from individual Demodex mites (Acari: Demodicidae)

The study for the first time attempted to accomplish 18S ribosomal DNA (rDNA) complete sequence amplification and analysis for three Demodex species (Demodex folliculorum, Demodex brevis and Demodex canis) based on gDNA extraction from individual mites. The mites were treated by DNA Release Additive and Hot Start II DNA Polymerase so as to promote mite disruption and increase PCR specificity. Determination of D. folliculorum gDNA showed that the gDNA yield reached the highest at 1 mite, tending to descend with the increase of mite number. The individual mite gDNA was successfully used for 18S rDNA fragment (about 900 bp) amplification examination. The alignments of 18S rDNA complete sequences of individual mite samples and those of pooled mite samples ( ≥ 1000mites/sample) showed over 97% identities for each species, indicating that the gDNA extracted from a single individual mite was as satisfactory as that from pooled mites for PCR amplification. Further pairwise sequence analyses showed that average divergence, genetic distance, transition/transversion or phylogenetic tree could not effectively identify the three Demodex species, largely due to the differentiation in the D. canis isolates. It can be concluded that the individual Demodex mite gDNA can satisfy the molecular study of Demodex. 18S rDNA complete sequence is suitable for interfamily identification in Cheyletoidea, but whether it is suitable for intrafamily identification cannot be confirmed until the ascertainment of the types of Demodex mites parasitizing in dogs.

Usefulness of estimated surface area of damaged skin as a proxy of mite load in the monitoring of sarcoptic mange in free-ranging populations of Iberian wild goat, Capra pyrenaica

In this study we examined the influence of several factors, like the surface of skin with lesions attributable to Sarcoptes scabiei, the time of year and host sex and age on variations of mite load in Iberian wild goats, Capra pyrenaica, from the Sierra Nevada Natural Space, southern Spain. As well, the surface area of skin with scabietic lesions estimated during field surveys were compared with measurements taken in the laboratory and the potential for using categories based on surface areas estimated during monitoring and management programs was analyzed. The surface area of the skin lesions measured in the laboratory and the time of year were the main factors affecting mite load. Results also revealed discrepancies between the surface area of lesions estimated in the field and those measured in the laboratory. The highest error percentages were associated with lesions ranging between 25 and 75% of host skin surface area. By reducing the number of categories of mange infestation (from 5 to 3) the proportion of cases correctly classified using data from field surveys increases. Our analyses suggest that the estimated surface areas of scabietic lesions is a useful relative index of mite abundance and/or intensity of parasitation in Iberian wild goat. Therefore, we conclude that revised classifications should be used in the monitoring of sarcoptic mange in wild populations, since data can be obtained in an inexpensive, fast and non-invasive fashion.