Population identification and divergence threshold in Psoroptidae based on ribosomal ITS2 and mitochondrial COI genes

Ectoparasites of the European wildcat (Felis silvestris) in Germany

Understanding the impact of parasites on wildlife populations is an important aspect of conservation management. However, research on ectoparasites in wildlife can be difficult, as examinations of live animals which are not habituated to human handling are often impossible. The European wildcat (Felis silvestris) is a strictly protected wildlife species whose population has been recovering in Germany in recent decades. Several studies from different European countries have investigated the parasitological status of European wildcat populations. However, most of these studies assessed endoparasite infections, whereas ectoparasite infestations have often been neglected. To fill this knowledge gap for wildcats in Germany, 131 dead found specimens were examined for ectoparasites by macroscopic and microscopic examination of the fur and the ear canals. Infestation with ectoparasites was present in 84.0% (110/131) of the wildcats. Ticks showed the highest prevalence with 72.5% (95/131) of wildcats infested, with 49.6% (65/131) infested with Ixodes ricinus and 36.6% (48/131) with Ixodes hexagonus/canisuga. A total of 27.5% (36/131) of the wildcats were positive for at least one flea species. Of the nine different flea species identified by morphology and/or molecular analyses, Ceratophyllidae were most common (16.8% [22/131]), with Ceratophyllus sciurorum confirmed on 12.2% (16/131) and Nosopsyllus fasciatus on 1.5% (2/131) animals, followed by Pulex irritans (5.3% [7/131]), Spilopsyllus cuniculi (3.8% [5/131]), Chaetopsylla spp. (3.1% [4/131]) (2/131 Chaetopsylla trichosa and 1/131 Chaetopsylla globiceps), Ctenocephalides felis (1.5% [2/131]), Archaeopsylla erinacei (1.5% [2/131]) and Ctenophthalmus baeticus (0.8% [1/131]). Further, 23.7% (31/131) of the wildcats harboured mites, identified as Trombicula autumnalis in 12.2% (16/131) and Otodectes cynotis in 4.8% (6/124) of cases. The only louse species detected was Felicola hercynianus with a prevalence of 2.3% (3/131). Infestation intensities ranged from 1 to 86 ticks, 1-49 fleas, 1-1896 mites, and 1-92 F. hercynianus per wildcat. This study demonstrates that a variety of ectoparasites infests wildcats in Germany, but they do not seem to have a serious impact on the general health of wildcats, as judged by the hosts' mostly good or very good nutritional condition. In addition, the potential risk to domestic cats (Felis catus) and humans posed by the wildcats' ectoparasites, appears to be low but present.

Discovery and demonstration of the temperature stress response functions of Dermatophagoides farinae proteins 1 and 2

BACKGROUND

Dermatophagoides farinae proteins (DFPs) are abundantly expressed in D. farinae; however, their functions remain unknown. Our previous transcriptome sequencing analyses revealed that the basal expression of DFP1 and DFP2 in D. farinae was high and, more importantly, upregulated under temperature stress. Therefore, DFPs were speculated to exert a temperature stress response function.

RESULTS

Real-time quantitative polymerase chain reaction detection revealed that both DFP1 and DFP2 were significantly upregulated under temperature stress. Particularly, DFP1 was upregulated under cold stress. Electrophoresis of D. farinae total proteins revealed an increased abundance of DFP1 and DFP2 (40-55 kDa bands) under temperature stress, which was corroborated by the mass spectrometry results. After silencing DFP1 and DFP2 further, temperature stress led to decreases in gene expression and survival rates. Moreover, DFP1 was identified as the upstream regulator of DFP2.

CONCLUSION

This study highlights the temperature stress response functions of DFP1 and DFP2 at the mRNA and protein levels. These results provide important insights for applying DFP1 and DFP2 as potential target genes for the molecular prevention and control of D. farinae to prevent allergic diseases. The newly established methods provide methodological guidance for the study of genes with unknown functions in mites.

Identification of Glycycometus malaysiensis (for the first time in Brazil), Blomia tropicalis and Dermatophagoides pteronyssinus through multiplex PCR

Blomia tropicalis and Dermatophagoides pteronyssinus play an important role in triggering allergy. Glycycometus malaysiensis causes IgE reaction in sensitive people, but is rarely reported in domestic dust, because it is morphologically similar to B. tropicalis making the identification of these species difficult. The identification of mites is mostly based on morphology, a time-consuming and ambiguous approach. Herein, we describe a multiplex polymerase chain reaction (mPCR) assay based on ribosomal DNA capable to identify mixed cultures of B. tropicalis, D. pteronyssinus and G. malaysiensis, and/or to identify these species from environmental dust. For this, the internal transcribed spacer 2 (ITS2) regions, flanked by partial sequences of the 5.8S and 28S genes, were PCR-amplified, cloned and sequenced. The sequences obtained were aligned with co-specific sequences available in the GenBank database for primer design and phylogenetic studies. Three pairs of primers were chosen to compose the mPCR assay, which was used to verify the frequency of different mites in house dust samples (n = 20) from homes of Salvador, Brazil. Blomia tropicalis was the most frequent, found in 95% of the samples, followed by G. malaysiensis (70%) and D. pteronyssinus (60%). Besides reporting for the first time the occurrence of G. malaysiensis in Brazil, our results confirm the good resolution of the ITS2 region for mite identification. Furthermore, the mPCR assay proved to be a fast and reliable tool for identifying these mites in mixed cultures and could be applied in future epidemiological studies, and for quality control of mite extract production for general use.

The Common Occurrence of Theileria ovis in Tibetan Sheep and the First Report of Theileria sinensis in Yaks from Southern Qinghai, China

PURPOSE

The tick-borne protozoa piroplasms, including Theileria and Babesia, are the cause of substantial economic losses to the livestock industry. However, in southern Qinghai province, China, there are limited information on the molecular characteristics of piroplasms. This study therefore aimed at determining the prevalence and genetic diversity of piroplasms.

METHODS

In order to detect piroplasms, we examined 330 yaks and 236 Tibetan sheep blood samples by nested PCR. The differences in piroplasms prevalence in relation to different risk factors was analyzed using SPSS 26. Phylogenetic analysis based on 18S rRNA sequences was inferred using MEGA 7.

RESULTS

During this study, Theileria spp. were detected in 33.6% (111/330) of yaks and 94.1% (222/236) of Tibetan sheep, but no Babesia was identified. Importantly, a comparison study revealed that T. ovis infection was highly prevalent in sheep (94.1%) but infrequent in yaks (6.1%), while T. sinensis was host-specific to yaks with an infection rate of 27.6%. In addition, male animals were more likely to be infected by T. sinensis and female animals were more likely to be infected by T. ovis. And animals below 4000 m areas reported a higher infection rate with T. sinensis (26.1% vs. 2.9%, p < 0.001). Alongside these differences in prevalence, we found a significantly higher T. sinensis infection rate in separated-grazing livestock (22.2% vs. 3.7%, p < 0.001), while mixed-grazing ruminants had a higher T. ovis infection rate (50.0% vs. 39.0%, p = 0.014). Furthermore, sequence analysis revealed that the 18S rRNA sequences obtained in this study shared 86.9-100.0% identities with each other and they were clustered into T. sinensis or T. ovis.

CONCLUSION

To our knowledge, this is the first report of T. sinensis in Qinghai region. In addition, high prevalence of the generally sub-clinical T. ovis in sheep indicates extensive exposure to ticks and transmission of tick-borne pathogens with a significant economic impact. This study provides insights into the distribution and genetic diversity of Theileria in China.

Molecular Identification, Transcriptome Sequencing and Functional Annotation of Pulex irritans

PURPOSE

Pulex irritans are vectors of various zoonotic pathogens. However, molecular studies on P. irritans and flea-borne diseases are limited due to the lack of molecular data. This study aimed to conduct transcriptome sequencing, functional annotation, and pathogen analysis of P. irritans.

METHODS

Fleas collected from a dog were identified morphologically and molecularly. RNA was extracted for transcriptome sequencing and functional annotation. Open reading frames (ORFs) of unigenes were confirmed by employing bioinformatics strategies, and maximum likelihood (ML) trees were reconstructed based on the highly expressed genes of ejaculation globulin-specific 3-like protein, salivary protein, and actin for phylogenetic relationship analysis.

RESULTS

The obtained mitochondrial 16S rRNA gene sequences showed 99.71% of similarity with P. irritans obtained from GenBank database. Transcriptome sequencing generated 74,412 unigenes, of which 53,211 were functionally annotated. A total of 195 unigenes were assigned to fleas, of which 69 contained complete ORFs. Phylogenetic trees of both ejaculatory globulin and salivary protein genes demonstrated that P. irritans first clustered with Pulicidae sp., indicating the reliability of transcriptome data. It is noteworthy that 1070 unigenes were assigned to Hymenolepis microstoma and Dipylidium caninum, of which 62 contained complete ORFs. The phylogenetic tree of the actin gene showed that the unigenes had closer relationships with Echinococcus sp., suggesting the role of P. irritans as intermediate hosts of tapeworms.

CONCLUSION

The results of this study provide the possibility for functional exploration of important genes and lay foundations for the prevention and control of P. irritans and flea-borne diseases.

Traceback of the Psoroptes outbreak in British Columbian bighorn sheep (Ovis Canadensis)

Psoroptes are a non-burrowing, ectoparasitic, mange-causing mite that has been documented in American bighorn sheep populations throughout the 19th and 20th centuries; however, it was not seen on Canadian bighorn sheep until 2006. The aim of this study was to determine the potential source of the Psoroptes outbreak in Canadian bighorn sheep. Morphological and molecular analyses were used to compare mites recovered from outbreak-associated bighorn sheep, pet rabbits in Canada, and on historically infested bighorn sheep in the USA. The results revealed that Psoroptes acquired from the Canadian and outbreak-associated American bighorn sheep were morphologically more similar to those collected from rabbits than mites on historically infested bighorn sheep. Outer opisthosomal setae lengths measured an average of 81.7 μm (±7.7 μm) in outbreak associated bighorn mites, 88.9 μm (±12.0 μm) in rabbit mites and 151.2 μm (±16.6 μm) in historically infested bighorn mites. The opisthosomal lobe morphology of bighorn mites in the outbreak herds was also more similar to that of rabbit mites, previously described as P. cuniculi, than historically infested bighorn mites, which match previous descriptions of P. ovis. This finding was supported by DNA sequence data of the mitochondrial cytochrome B gene. This is the first report of Psoroptes of the rabbit ecotype on bighorn sheep. The morphological and molecular data therefore support the hypothesis that the source of Psoroptes outbreak in Canadian bighorn sheep represented a disease spillover event from rabbits rather than transmission from infested American bighorn sheep populations.

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Psoroptes infestations are not host specific.

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Canadian bighorn Psoroptes are morphologically distinct from USA bighorn Psoroptes.

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Mitochondrial DNA gene CytB can be used to differentiate Psoroptes strains.

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The Canadian bighorn sheep Psoroptes outbreak likely came from rabbits not USA bighorns.

Molecular identification and DNA barcode screening of acaroid mites in ground flour dust

Molecular identification of acaroid mites is difficult because of the scarcity of molecular data in GenBank. Here, acaroid mites collected from ground flour dust in Xi'an, China, were preliminarily morphologically classified/grouped. Universal primers were then designed to amplify and screen suitable DNA barcodes for identifying these mites. Sixty mite samples were morphologically classified into six groups. Groups 1-2 were identified to Dermatophagoides farinae and Tyrophagus putrescentiae, while Groups 3-6 were not identified to the species level. ITS2 exhibited higher efficiency in molecular identification in comparison with COI, 12S, and 16S. Groups 1-6 were identified as D. farinae, T. putrescentiae, Suidasia nesbitti, Chortoglyphus arcuatus, Lepidoglyphus destructor, and Gohieria sp., respectively. The phylogenetic results were consistent with the morphological classification. Group 6 was further identified as G. fusca according to the morphology of the reproductive foramen. We conclude that the use of ITS2 and the availability of universal primers provide an ideal DNA barcode for molecular identification of acaroid mites. The use of multiple target genetic markers in conjunction with morphological approaches will improve the accuracy of Acaridida identification.

Temperature stress response: A novel important function of Dermatophagoides farinae allergens

Dermatophagoides farinae, an important pathogen, has multiple allergens. However, their expression under physiological conditions are not understood. Our previous RNA-seq showed that allergens of D. farinae were up-regulated under temperature stress, implying that they may be involved in stress response. Here, we performed a comprehensive study. qRT-PCR detection indicated that 26 of the 34 allergens showed differential expression. Der f1 had the most abundant basic expression quantity. Der f 28.0201 (HSP70) and Der f3 had the same regulation pattern in 9 highly expressed transcripts, which only up-regulated at 41 °C and 43 °C, but Der f 28.0201 showed stronger regulation than Der f 3 (19.88-fold vs 6.02-fold). Whereas Der f 1, 2, 7, 21, 22, 27, and 30 were up-regulated under both heat and cold stress, and Der f 27 showed the strongest regulation ability among them. Der f 27 showed more significant up-regulation than Der f 28.0201 under heat stress (23.59-fold vs 19.88-fold), and Der f27 had more obvious up-regulation under cold than heat stress (30.70-fold vs 23.59-fold). The expression of Der f 27, 28.0201 and 1, and D. farinae survival rates significantly decreased following RNAi, indicating the upregulation of these allergens under temperature stress conferred thermo-tolerance or cold-tolerance to D. farinae. In this study, we described for the first time that these allergens have temperature-stress response functions. This new scientific discovery has important clinical value for revealing the more frequent and serious allergic diseases caused by D. farinae during the change of seasons.

Divergent domains of 28S ribosomal RNA gene: DNA barcodes for molecular classification and identification of mites

BACKGROUND

The morphological and molecular identification of mites is challenging due to the large number of species, the microscopic size of the organisms, diverse phenotypes of the same species, similar morphology of different species and a shortage of molecular data.

METHODS

Nine medically important mite species belonging to six families, i.e. Demodex folliculorum, D. brevis, D. canis, D. caprae, Sarcoptes scabiei canis, Psoroptes cuniculi, Dermatophagoides farinae, Cheyletus malaccensis and Ornithonyssus bacoti, were collected and subjected to DNA barcoding. Sequences of cox1, 16S and 12S mtDNA, as well as ITS, 18S and 28S rDNA from mites were retrieved from GenBank and used as candidate genes. Sequence alignment and analysis identified 28S rDNA as the suitable target gene. Subsequently, universal primers of divergent domains were designed for molecular identification of 125 mite samples. Finally, the universality of the divergent domains with high identification efficiency was evaluated in Acari to screen DNA barcodes for mites.

RESULTS

Domains D5 (67.65%), D6 (62.71%) and D8 (77.59%) of the 28S rRNA gene had a significantly higher sequencing success rate, compared to domains D2 (19.20%), D3 (20.00%) and D7 (15.12%). The successful divergent domains all matched the closely-related species in GenBank with an identity of 74-100% and a coverage rate of 92-100%. Phylogenetic analysis also supported this result. Moreover, the three divergent domains had their own advantages. D5 had the lowest intraspecies divergence (0-1.26%), D6 had the maximum barcoding gap (10.54%) and the shortest sequence length (192-241 bp), and D8 had the longest indels (241 bp). Further universality analysis showed that the primers of the three divergent domains were suitable for identification across 225 species of 40 families in Acari.

CONCLUSIONS

This study confirmed that domains D5, D6 and D8 of 28S rDNA are universal DNA barcodes for molecular classification and identification of mites. 28S rDNA, as a powerful supplement for cox1 mtDNA 5'-end 648-bp fragment, recommended by the International Barcode of Life (IBOL), will provide great potential in molecular identification of mites in future studies because of its universality.

Stress response and silencing verification of heat shock proteins in Dermatophagoides farinae under temperature stress

Dermatophagoides farinae is a major exogenous allergen. Its ability to tolerate adverse external temperatures makes it responsible for widespread occurrence of allergies. Heat shock protein (HSP), a recognized temperature stress response gene, but its role in D. farinae remained unclear. Here, we performed a comprehensive study. First, we found that 25 °C was the optimal temperature, and all mites died at 48 or -20 °C for 1 h (LT100). Thus, 41 °C (LT15), 43 °C (LT25), 45 °C (LT45), and -10 °C (LT25) were selected as stress temperatures to perform de novo RNA-seq. Then, 17 main genes of the 47 differentially expressed HSP, were detected by qRT-PCR. Temperature and time gradient versus expression magnitude histogram revealed that HSP70, HSP83-1, HSP83-2, and HSP16-1 showed heat stress response only at 41-43 °C, while HSC71 and HSF played a regulatory role under both heat and cold stress, particularly HSF, with strong intensity, long duration, and quick upregulation at recovery for 10-20 min. Finally, gene expression and D. farinae survival rates significantly decreased following RNAi. These findings indicated that HSPs conferred thermo-tolerance or cold-tolerance to D. farinae. In conclusion, this was the first meaningful exploration that confirmed HSP and HSF playing an important role in temperature resistance of D. farinae.

De Novo RNA-seq and Functional Annotation of Haemaphysalis longicornis

PURPOSE

Haemaphysalis longicornis (Neumann) is a hematophagous tick widely distributed in northern China. It not only causes enormous economic loss to animal husbandry, but also as a vector and reservoir of various zoonotic pathogens, it spreads natural focal diseases, such as severe fever with thrombocytopenia syndrome, seriously threatening human health. Lack of transcriptomic and genomic data from H. longicornis limits the study of this important medical vector.

METHODS

The engorged female H. longicornis from Gansu, China, was used for RNA extraction, de novo RNA-seq, functional annotation, and ORF prediction.

RESULTS

As a result, 53.09 million clean reads (98.88%) with a GC content of 54.29% were obtained. A total of 65,916 Unigenes were assembled, of which 34.59% (23,330) were successfully annotated. Of these Unigenes, 22,587 (34.27%) were annotated to species by NCBI non-redundant protein (nr). Ixodes scapularis, Limulus polyphemus, Parasteatoda tepidariorum, Stegodyphus mimosarum, and Metaseiulus occidentalis were the top BLAST hit species, accounting for 47.23%, 9.58%, 4.11%, 3.50%, and 2.69%, respectively. A total of 29,182 ORFs were predicted, and 35 complete ORFs for functional genes were identified, including ORFs involved in digestion (14), stress responses (8), anticoagulation (3), reproduction (3), antimicrobial (2), drug resistance (2), movement (2), autophagy (1), and immunity (1), respectively. The Unigene ORFs encoding cathepsin and heat shock proteins were further analyzed phylogenetically.

CONCLUSION

De novo RNA-seq and functional annotation of H. longicornis were successfully completed for the first time, providing a molecular data resource for further research on blood-sucking, pathogen transmission mechanisms, and effective prevention and control strategies.

Screening of reference genes and quantitative real-time PCR detection and verification in Dermatophagoides farinae under temperature stress

Dermatophagoides farinae is an important source of indoor allergens that shows strong tolerance to external temperatures. However, the regularity and mechanism of tolerance are still unclear. Based on our previous RNA-seq and annotation of D. farinae under temperature stress, it is planned to identify differentially expressed genes (DEGs) involved in the temperature stress response by quantitative real-time PCR (qRT-PCR). However, the lack of reference genes directly limited the detection and confirmation of DEGs. Accordingly, in this study, we have selected six candidates as reference genes in D. farinae: 60S RP L11, 60S RP L21, α tubulin, GAPDH, Der f Mal f 6, and calreticulin, and evaluated their expression stabilities as affected by heat and cold stresses, using geNorm, NormFinder, BestKeeper, comparative ΔCt and RefFinder methods. Then the expression level of 15 DEGs were detected and verified. geNorm analysis showed that α tubulin and calreticulin were the most stable reference genes under heat stress and cold stress of D. farinae. Similar evaluation results were obtained by NormFinder and BestKeeper, in which 60S RP L21 and α tubulin were the most stable reference genes. By comparative ΔCt method and a comprehensive evaluation of RefFinder, α tubulin was identified as the most ideal reference gene of D. farinae under heat and cold stresses. Furthermore, qRT-PCR detection results of 15 DEGs were almost identical to the RNA-seq results, indicating that α tubulin is stable as a reference gene. This study provided technical support for DEGs expression studies in D. farinae using qRT-PCR.

Acaricidal activity of plant-derived essential oil components against Psoroptes ovis in vitro and in vivo

BACKGROUND

Treatment of Psoroptes ovis in cattle is limited to topical acaricides or systemic treatment with macrocyclic lactones. Treatment failure of macrocyclic lactones has been reported. The aim of this study was to evaluate a potential alternative treatment against P. ovis.

METHODS

The acaricidal activity against P. ovis of four plant-derived essential oil components, i.e. geraniol, eugenol, 1,8-cineol and carvacrol, was assessed in vitro and in vivo. In vitro contact, fumigation and residual bioassays were performed. In addition, 12 Belgium Blue cattle were artificially infested and treated topically once a week for three successive weeks with carvacrol in Tween-80 (treatment group) or with Tween-80 alone (control). The efficacy of carvacrol was determined by the reduction in lesion size and mite counts. Six additional animals were topically treated with carvacrol to assess local adverse reactions.

RESULTS

Three components showed a concentration-dependent acaricidal activity in a contact assay, with LC50 of 0.56, 0.38 and 0.26% at 24 h for geraniol, eugenol, and carvacrol, respectively. However, 1,8-cineol showed no activity at any of the tested concentrations in a contact bioassay. In a fumigation bioassay, carvacrol killed all mites within 50 min after treatment, whereas geraniol, eugenol and 1,8-cineol needed 90 to 150 min. Following a 72 h incubation period in a residual bioassay, carvacrol killed all mites after 4 h of exposure to LC90, while geraniol and eugenol killed all mites only after 8 h exposure. Based on these results, carvacrol was further assessed in vivo. Mite counts in the treatment group were reduced by 98.5 ± 2.4% at 6 weeks post-treatment, while in the control group the mite population had increased. Topical application of carvacrol only caused mild and transient erythema 20 min after treatment. No other side effects were observed.

CONCLUSIONS

Considering the strong acaricidal activity of carvacrol in vitro and in vivo and the mild and transient local side effects, carvacrol shows potential as an acaricidal agent in the treatment of P. ovis in cattle.

The Construction of Full-Length cDNA Library for Otodectes cynotis

BACKGROUND

Otodectes cynotis (Hering, 1838) is the pathogen of otodectic mange distributed worldwide. The mite mainly infests carnivores and, sometimes, humans. However, due to the lack of cDNA library, research on its pathogenesis has been challenging.

METHODS

To solve this problem, the present study first sampled O. cynotis mites from an infested cat from Xi'an, China, for RNA extraction. Then, the full-length cDNA library was constructed using the SMART technique. Finally, positive clones > 500 bp and Hsc70-5 gene fragment specifically amplified from the cDNA library were sequenced and analyzed to verify the library's reliability.

RESULTS

Results showed that RNA extracted from 300 mites had good quality with a concentration of 149 ng/μl and OD260/OD280 of 1.99. The library satisfied the quality standard of a good library with a titer of 5.02 × 10⁵ PFU/ml and a combination rate of 97.61%. In addition, clone 4 and Hsc70-5 showed 98.38% and 99.72% identity with Ef1-α and Hsc70-5 gene sequences of O. cynotis in GenBank, respectively.

CONCLUSION

The cDNA library of O. cynotis constructed here was successful and reliable, creating the basis for research on RNA sequencing and functional genes of O. cynotis.

DNA barcoding for molecular identification of Demodex based on mitochondrial genes

There has been no widely accepted DNA barcode for species identification of Demodex. In this study, we attempted to solve this issue. First, mitochondrial cox1-5' and 12S gene fragments of Demodex folloculorum, D. brevis, D. canis, and D. caprae were amplified, cloned, and sequenced for the first time; intra/interspecific divergences were computed and phylogenetic trees were reconstructed. Then, divergence frequency distribution plots of those two gene fragments were drawn together with mtDNA cox1-middle region and 16S obtained in previous studies. Finally, their identification efficiency was evaluated by comparing barcoding gap. Results indicated that 12S had the higher identification efficiency. Specifically, for cox1-5' region of the four Demodex species, intraspecific divergences were less than 2.0%, and interspecific divergences were 21.1-31.0%; for 12S, intraspecific divergences were less than 1.4%, and interspecific divergences were 20.8-26.9%. The phylogenetic trees demonstrated that the four Demodex species clustered separately, and divergence frequency distribution plot showed that the largest intraspecific divergence of 12S (1.4%) was less than cox1-5' region (2.0%), cox1-middle region (3.1%), and 16S (2.8%). The barcoding gap of 12S was 19.4%, larger than cox1-5' region (19.1%), cox1-middle region (11.3%), and 16S (13.0%); the interspecific divergence span of 12S was 6.2%, smaller than cox1-5' region (10.0%), cox1-middle region (14.1%), and 16S (11.4%). Moreover, 12S has a moderate length (517 bp) for sequencing at once. Therefore, we proposed mtDNA 12S was more suitable than cox1 and 16S to be a DNA barcode for classification and identification of Demodex at lower category level.

Improvement on the extraction method of RNA in mites and its quality test

To solve the long-existing difficult problems in extracting RNA and constructing a complementary DNA (cDNA) library for trace mites, we conducted a further comparative experiment among three RNA extraction methods (TRIzol method, Omega method, and Azanno method) based on our previous attempts at the construction of cDNA library of mites, with Psoroptes cuniculi still used as the experimental subject. By subsequently decreasing the number of mites, the least number of mites needed for RNA extraction of each method were found by criteria of completeness, concentration, and purity of the extracted RNA. Specific primers were designed according to the allergen Pso c1, Pso c2, and Actin gene sequences of Psoroptes to test the reliability of cDNA library. The results showed that Azanno method needed only 10 mites with sensitivity 204 times higher than previously used TRIzol method and 20 times higher than Omega method; clear RNA band was detected by agarose gel electrophoresis; and ultraviolet spectrophotometer determination showed that RNA concentration, 260/280, and 260/230 were in the range of 102 to 166 ng/μl, 1.83 to 1.99, and 1.49 to 1.72, respectively. Finally, specific primers detection showed that the amplified sequences had 98.33, 98.19, and 99.52% identities with those of P. cuniculi or Psoroptes ovis in GenBank, respectively, indicating that the cDNA library constructed using 10 mites was successful and it could meet the requirements for molecular biology research. Therefore, we concluded that Azanno method was more effective than TRIzol method and Omega method in RNA extraction and cDNA library construction of trace mites.