Poultry Red Mite Research Articles

Surface hydrophobicity mechanism of poultry red mite, Dermanyssus gallinae (Acari: Dermanyssidae), gives novel meaning to chemical control

Surface hydrophobicity of organisms provides biological self-protection. The hydrophobicity of pest surface, acting as a main obstacle for the pest control, can lead to low utilization and high loss of pesticides. Dermanyssus gallinae is a notorious pest in egg-laying hens, whose control primarily depends on acaricide spraying, while its surface hydrophobicity and potential influence on pesticide effectiveness are not clear. In the present study, the contact angle measurements revealed that the surface of D. gallinae was hydrophobic. Analysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the surface microstructures of D. gallinae consist of cuticular folds, with a lipid-rich outermost layer of the cuticle. Based on gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC), it was found that the major compositions of cuticular lipids were fatty acids and n-alkanes. Modifying the chemical compositions and microstructures of the D. gallinae surface resulted in a reduction in surface hydrophobicity and an increase in the permeation of Rhodamine B through the cuticle. This observation suggested that the chemical compositions and microstructures were pivotal in determining surface hydrophobicity, hindering compound penetration into the cuticle. Finally, it was found improving the wettability of pesticide solution by adding surfactants could overcome the surface hydrophobicity and enhance the efficacy of pesticide against the mites. This study sheds light on the surface hydrophobicity mechanism of D. gallinae and provides a novel strategy to improve the efficacy of acaricides against the mites.

Evaluation of acaricidal activity in entomopathogenic fungi for poultry red mite (Dermanyssus gallinae) control

The poultry red mite (PRM), Dermanyssus gallinae, significantly impacts the health of egg-laying hens. Mites feed on the blood of infested chickens and have a great economic impact on the poultry industry. Chemical treatment of mites raises concerns about their resistance to miticides and residues in eggs and poultry. Biocontrol using entomopathogenic fungi is expected to be a chemical-free strategy for reducing PRM infestations. Therefore, the present study aimed to investigate the effects of various entomopathogenic fungal species collected in South Korea on the inhibition of PRM. Seventeen strains of six fungal species collected from various sources were used to evaluate acaricidal activity against PRM. The results showed that 16/17 strains had acaricidal properties against PRM, of which strains of Metarhizium anisopliae had the highest acaricidal activity. Mites treated with M. anisopliae CBNU 4–2 showed 100 % mortality 5 d after inoculation, followed by M. flavoviride var. pemphigi. The M. flavoviride var. pemphigi CBNU 1–1–1 showed 97.78 % mortality after 10 d of exposure to fungi. The mortality rate of PRM treated with other strains slowly increased and reached its highest value on the 14th day of inoculation. The results of this study provide information on the acaricidal activity of different entomopathogenic fungi against PRM. This information is important for the selection of fungal species for developing biocontrol methods for PRM treatment. These strains could be used for further evaluation of PRM treatment on chicken farms, or in combination with other methods, to increase PRM treatment efficiency.

Molecular detection of avian pathogens in poultry red mite (Dermanyssus gallinae) in Algerian layer farms as a potential predictive tool

The poultry red mite Dermanyssus gallinae is a hematophagous ectoparasite of layer hens. Infestations with poultry red mites pose an increasing threat to the egg production industry, causing serious problems to animal health and welfare, directly or indirectly as a vector of several infectious agents. In this study, we aimed to investigate common avian pathogens in mites. The mite samples were collected from 58 poultry farms in 7 regions accounting for more than 70 % of the national egg production in Algeria. The presence of 13 avian pathogens was detected using DNA and RNA samples from mites collected. Results revealed significant associations between PRM and potential pathogens such as Escherichia coli, Salmonella enterica, fowlpox virus, and gallid herpesvirus 1. Pathogen detection in Dermanyssus gallinae could serve as an early diagnostic or a risk analysis tool for infectious diseases in poultry farms, facilitating effective disease management strategies. Despite further research being necessary to address uncertainties, such a strategy could be used to enhance the integrated management of poultry health.

Morphological changes in plasma-exposed poultry red mites (Dermanyssus gallinae) using high-resolution video camera and optical coherence tomography (OCT)

Dermanyssus gallinae, the poultry red mite (PRM), is a hematophagous temporary ectoparasite that causes serious economic losses and animal health impairment on laying hen farms worldwide. Control is limited by the parasite’s hidden lifestyle, restrictions on the use of chemical acaricides and the development of resistance against certain drug classes. As a result, research was conducted to explore alternative control methods. In recent years, atmospheric pressure plasma has been increasingly reported as an alternative to chemical acaricides for pest control. This physical method has also shown promising against PRM under laboratory conditions. However, the detailed mechanisms of action have not yet been elucidated. In the present study, the effects of cold atmospheric pressure plasma on PRM were investigated using digital videography and optical coherence tomography (OCT), an imaging technique that visualizes the topography of surfaces and internal structures. Digital videography showed that a redistribution of the contents of the intestinal tract and excretory organs (Malpighian tubules) occurred immediately after plasma exposure. The body fluids reached the distal leg segments of PRM and parts of the haemocoel showed whiter and denser clumps, indicating a coagulation of the haemocoel components. OCT showed a loss of the boundaries of the hollow organs in transverse and sagittal sectional images as well as in the three-dimensional image reconstruction. In addition, a dorso-ventral shrinkage of the idiosoma was observed in plasma-exposed mites, which had shrunk to 44.0% of its original height six minutes after plasma exposure.

Point mutations in the voltage-gated sodium channel gene conferring pyrethroid resistance in China populations of the Dermanyssus gallinae.

Dermanyssus gallinae, the poultry red mite (PRM), is a worldwide ectoparasite posing significant economic challenges in poultry farming. The extensive use of pyrethroids for PRM control has led to the emergence of pyrethroid resistance. The objective of this study is to detect the pyrethroid resistance and explore its associated point mutations in the voltage-gated sodium channel (VGSC) gene among PRM populations in China. Several populations of D. gallinae, namely CJF-1, CJP-2, CJP-3, CSD-4 and CLD-5, displayed varying degrees of resistance to beta-cypermethrin compared to a susceptible field population (CBP-5). Mutations of VGSC gene in populations of PRMs associated with pyrethroid resistance were identified through sequencing its fragments IIS4-IIS5 and IIIS6. The mutations I917V, M918T/L, A924G and L925V were present in multiple populations, while no mutations were found at positions T929, I936, F1534 and F1538. The present study confirmed the presence of extremely high levels of pyrethroid resistance in PRM populations in China, and for the first time detected four pyrethroid resistance mutations in the VGSC gene. Identifying pyrethroid resistance in the field population of PRM in China can be achieved through screening for VGSC gene mutations as an early detection method. Our findings underscore the importance of implementing chemical PRM control strategies based on resistance evidence, while also considering the management of acaricide resistance in the control of PRMs. © 2024 Society of Chemical Industry.

Administering Fluralaner in Drinking Water for Treatment of Dermanyssus gallinae Infestation in Hy-Line W80 Laying Hens

Background: Poultry red mites, or Dermanyssus gallinae, pose a threat to the welfare and productivity of laying hens. Moreover, the increasing resistance of these mites to conventional miticides highlights the urgent need for alternative treatment options. There are also documented cases of poultry red mite infestations in humans. Objectives: The primary objective of this study was to evaluate the efficacy of fluralaner against Dermanyssus gallinae infestation in hens. Methods: Fluralaner was selected as a novel treatment for poultry red mite due to its effectiveness and safety profile. The presence of live mites in the drinking water tank served as the indicator of infestation. Live mites were counted on nine occasions throughout the study. Fluralaner was administered at three doses of 0.5 mg/kg in drinking water with a seven-day interval between each dose. The efficacy of fluralaner was assessed, with an efficacy percentage exceeding 90% considered indicative of antiparasitic efficacy. Results: The overall efficacy of Fluralaner in the current study exceeded 90% by day 5 and reached 100% by day 17. Conclusions: This study demonstrates that fluralaner is an effective alternative treatment, achieving efficacy rates exceeding 90% against poultry red mite infestation in laying hens.

Spatial Distribution of Dermanyssus gallinae Infestations in Greece and Their Association with Ambient Temperature, Humidity, and Altitude.

Dermanyssus gallinae, the poultry red mite (PRM), is the most prevalent and harmful ectoparasite of laying hens globally. Although prevalence and risk factor studies can help veterinarians make decisions regarding farm treatments, relevant data are scarce. The present study investigated the prevalence and infestation severity of PRM in poultry farms across Greece and examined potential risk factors. AviVet traps were used to sample 84 farms (51 backyard, 33 industrial) over three years. Farm altitude, temperature, humidity, region, and production systems were assessed as potential risk factors with chi-square tests, initially for all the studied farms and then exclusively for backyard farms. The overall prevalence was 75.0% and was higher in backyard farms (80.4%) compared with industrial ones (66.7%), varying regionally from 66.7 to 90.9%. Altitude and temperature were not significant risk factors, but farms with humidity <60% had a lower infestation risk. Infestation severity did not significantly differ by risk factors. The poultry red mite is highly prevalent across Greek poultry production systems and regions. In the future, global warming, reduced acaricide options, and a ban on cage systems will all threaten a wider spatio-temporal distribution of the PRM, justifying the urgent need for effective monitoring and control methods to protect hen production and welfare and workers' health.

The Poultry Red Mite, Dermanyssus gallinae, travels far but not frequently, and takes up permanent residence on farms

Management of Dermanyssus gallinae, a cosmopolitan hematophagous mite responsible for damage in layer poultry farming, is hampered by a lack of knowledge of its spatio-temporal population dynamics. Previous studies have shown that the circulation of this pest between farms is of strictly anthropogenic origin, that a mitochondrial haplogroup has been expanding on European farms since the beginning of the 21st century and that its local population growth may be particularly rapid. To refine our understanding of how D. gallinae spreads within and among farms, we characterized the genetic structure of mite populations at different spatial scales and sought to identify the main factors interrupting gene flow between poultry houses and between mitochondrial haplogroups. To this end, we selected and validated the first set of nuclear microsatellite markers for D. gallinae and sequenced a region of the CO1-encoding mitochondrial gene in a subsample of microsatellite-genotyped mites. We also tested certain conditions required for effective contamination of a poultry house through field experimentation, and conducted a survey of practices during poultry transfers. Our results confirm the role of poultry transport in the dissemination of mite populations, but the frequency of effective contamination after the introduction of contaminated material into poultry houses seems lower than expected. The high persistence of mites on farms, even during periods when poultry houses are empty and cleaned, and the very large number of nodes in the logistic network (large number of companies supplying pullets or transporting animals) undoubtedly explain the very high prevalence on farms. Substantial genetic diversity was measured in farm populations, probably as a result of the mite's known haplodiploid mode of sexual reproduction, coupled with the dense logistic network. The possibility of the occasional occurrence of asexual reproduction in this sexually reproducing mite was also revealed in our analyses, which could explain the extreme aggressiveness of its demographic dynamics under certain conditions.

Entomopathogenic fungi with biological control potential against poultry red mite (Dermanyssus gallinae, Arachnida: Dermanyssidae)

The poultry red mite, Dermanyssus gallinae (Arachnida: Dermanyssidae) is a pest that causes significant economic loss in laying hens for which control methods are limited. In this study, the effects of 20 indigenous fungal strains on poultry red mites in chicken farms were investigated. All experiments were conducted under laboratory condition at 28 ± 1 °C and 80 ± 5% humidity. A screening test showed that Metharizium flavoviride strain As-2 and Beauveria bassiana strain Pa4 had the greatest measured effect on D. gallinae at 1 × 107 conidia/ml 7 days after application. In a subsequent does-response experiment, these strains also caused 92.7% mortality at 1 × 109 conidia/ml within the same period. The LC50 of these strains was 5.5 × 104 (95% CI: 0.8–37.5) conidia/ml for As-2 and 3.2 × 104 (95% CI: 0.4–26.0) conidia/ml for Pa4, and their LT50 were 1.94 and 1.57 days, respectively. The commercial Metarhizium anisopliae bioinsecticide Bio-Storm 1.15% WP, used as a comparator, had LC50 and LT50 1 × 105 (95% CI: 0.1–7.9) conidia/ml and 3.03 (95% CI: 2.4–3.8) days, respectively. It is suggested that mycoacaricides could be developed using the best two fungal strains found in this study (As-2 and Pa4), providing potential for biological control of poultry red mites.

Screening of avian pathogens and genetic analysis of several mitochondrial genes in Dermanyssus gallinae populations in Türkiye&lt;/p &gt;

The poultry red mite, PRM, Dermanyssus gallinae (De Geer, 1778), is widely regarded as the primary ectoparasite affecting egg-laying hens around the world. Besides direct feeding damage, the transmission of avian pathogens by PRMs is also a significant concern. Therefore, we aimed to screen the presence of 14 common avian pathogens in 32 PRM populations from egg-laying hens in Türkiye. As a result, Salmonella enterica (n=3), Tsukamurella paurometabola (n=18), and Avian fowlpox virus (n=4) (3 of which were wild-type APV) were detected in tested PRM populations. The results showed that the prevalence of avian pathogens in Turkish PRM populations was low. Nevertheless, these findings suggested that PRM can harbor disease-causing agents and may act as a vector in the spread of these pathogens in farms. In addition, four mitochondrial genes (mtDNAs) of D. gallinae, namely ND4, ND5, cytb, and atp6, were amplified, and obtained sequences were submitted to the GenBank database for the first time, which will allow further analyses. The genetic variation within cytb sequences of Turkish PRMs was the highest (1.01%), whereas intra-specific genetic distance was 1.7% when compared to a Chinese population (only available cytb sequence in the GenBank), indicating increasing genetic differentiation by distance. Last, more sequences belonging to mitochondrial genes are required to reveal their potential as molecular markers.

In Vivo Characterization of the Anti-Glutathione S-Transferase Antibody Using an In Vitro Mite Feeding Model.

Poultry red mites (Dermanyssus gallinae, PRMs), tropical fowl mites (Ornithonyssus bursa, TFMs), and northern fowl mites (O. sylviarum, NFMs) are blood-feeding pests that debilitate poultry worldwide. Glutathione S-transferase (GST) plays an important role in the detoxification and drug metabolism of mites. However, research on avian mite GSTs as vaccine antigens is still lacking. Therefore, we aimed to evaluate the potential of avian mite GSTs for vaccine development. We identified GST genes from TFMs and NFMs. We prepared recombinant GST (rGST) from TFMs, NFMs, and PRMs, and assessed their protein functions. Moreover, we evaluated the cross-reactivity and acaricidal effect of immune plasma against each rGST on TFMs, NFMs, and PRMs. The deduced amino acid sequences of GSTs from TFMs and NFMs were 80% similar to those of the PRMs. The rGSTs exhibited catalytic activity in conjugating glutathione to the 1-chloro-2,4-dinitrobenzene substrate. Immune plasma against each rGST showed cross-reactivity with rGST from different mite species. Moreover, the survival rate of PRMs fed with immune plasma against the rGST of TFMs and NFMs was significantly lower than that of the control plasma. These results demonstrate the potential application of GST as an antigen for the development of a broad-spectrum vaccine against avian mites.

A semi-nested PCR method with increased sensitivity for the specific, direct detection of Salmonella enterica strains in poultry ectoparasites.

The darkling beetle, Alphitobius diaperinus, and the poultry red mite, Dermanysuss gallinae are among the most common pests of poultry farms. Both pests can be carriers and reservoirs of various pathogens including zoonotic ones like Salmonella. Salmonellosis is one of the most common foodborne diseases reported in the EU. We developed a semi-nested PCR method for the direct detection of Salmonella enterica. When testing the specificity of the novel PCR, we successfully detected various S. enterica strains, whereas Escherichia coli and Citrobacter strains gave negative results. The authenticity of the PCR products was confirmed by DNA sequencing. The sensitivity of the semi-nested PCR was tested on serial dilution of bacterial cultures and extracted DNA. We found our new method more sensitive than the previous PCRs. We also screened ectoparasite samples, collected from a poultry farm in Hungary, and three out of the eight samples were positive for S. Enteritidis. This novel PCR seems suitable for the detection of S. enterica strains in poultry ectoparasites without the need of sample pre-enrichment.

Significant role of symbiotic bacteria in the blood digestion and reproduction of Dermanyssus gallinae mites.

Endosymbiotic bacteria significantly impact the fitness of their arthropod hosts. Dermanyssus gallinae, the poultry red mite, is a blood-feeding ectoparasite that exclusively feeds on avian blood. While there is a relatively comprehensive understanding of its microbial community structures across developmental stages based on 16S rRNA sequencing， the functional integration of these microbes within the host's physiology remains elusive. This study aims to elucidate the role of symbiotic bacteria in D. gallinae biology. 16S rRNA amplicon sequencing and fluorescence in situ hybridization revealed a prominent midgut-confinement bacterial microbiota with considerable diversity, out of which Kocuria and Bartonella A acted as the predominant bacterial genera inhabiting D. gallinae. The relative abundance of Bartonella A increased rapidly after blood-sucking, suggesting its adaptation to a blood-based diet and its pivotal role in post-engorgement activities. Some of the isolated bacterial strains from D. gallinae display hemolytic activity on blood agar, potentially aiding blood digestion. To corroborate this in vivo, antibiotic-mediated clearance was exploited to generate dysbiosed cohorts of D. gallinae mites, lacking some of the key bacterial species. Phenotypic assessments revealed that dysbiosed mites experienced delayed blood digestion and diminished reproductive capacity. Whole-genome sequencing identified Bartonella A as a new species within the genus Bartonella, exhibiting characteristics of an obligate symbiont. These findings underscore the significance of microbiota in poultry red mites and suggest microbiota-targeted strategies for controlling mite populations in poultry farms.

Successful long-term control of poultry red mite (Dermanyssus gallinae) infestations in floor-kept laying hens via integrated pest management—a case report

This case report describes the successful control of poultry red mite [PRM] (Dermanyssus gallinae) infestations in an experimental laying hen house via a combined use of cleaning and disinfection measure, the preventive application of a synthetic silica-based acaricide and frequent mite monitoring. The high number of PRM in the laying hen house was reduced by 99.8% by treatment with fluralaner (Exzolt®, MSD Animal Health Unterschleißheim, Germany; 0.5 mg/kg body weight via drinking water twice, 7 days apart). After the laying hens were removed, the hen house was dry-cleaned, wet-cleaned and disinfected. After drying, synthetic amorphous silica (Fossil Shield® instant white, Bein GmbH, Eiterfeld, Germany) was applied as a preventive measure before the hen house was restocked with pullets for two housing periods of 58 and 52 weeks. Over these periods (i.e. more than 2 years), no PRM was detected during mite monitoring at two-week intervals via tube traps and visual monitoring. This result therefore suggests that the combined use of appropriate chemical and physical prevention measures within an integrated pest management regime can be successfully used for the long-term control of PRM. This could reduce the use of acaricidal drugs, thereby helping maintain their efficacy.

Investigation of peripheral blood responses in chickens infested with Dermanyssus gallinae

Among haematophagous ectoparasites that infest chickens, poultry red mite (Dermanyssus gallinae, PRM) is one of the most serious threats to poultry farms. Mass PRM infestation causes various health problems in chickens, resulting in significant productivity reduction in the poultry industry. Despite the efficiency of acaricides for controlling PRMs, the emergence of acaricide-resistant PRMs represents a challenging setback. Infestation with haematophagous ectoparasites, such as PRMs, induces inflammatory and haemostatic reactions in the host. Therefore, we aimed to explore the gene expression in chicken peripheral blood cells to elucidate host responses against PRM infestation in detail. RNA sequencing of blood-fed PRMs was performed, and the levels of the chicken-derived transcripts obtained from the ingested blood cells were analysed. Genes encoding haemoglobin subunits were found to be significantly more expressed, suggesting that PRM infestation causes anaemia in chickens. Additionally, the mRNA and plasma concentrations of CC chemokine ligand 4 and β2 microglobulin among the immune-related molecules were found to be significantly higher in PRM-infested chickens compared with non-infested animals. These results suggest that PRM infestation induce inflammation in chicken. Further studies are warranted to better understand the influence of PRM infestation on the host physiological states, including immunity.

Characterization of cysteine proteases from poultry red mite, tropical fowl mite, and northern fowl mite to assess the feasibility of developing a broadly efficacious vaccine against multiple mite species.

Infestation with poultry red mites (PRM, Dermanyssus gallinae) causes anemia, reduced egg production, and death in serious cases, resulting in significant economic losses to the poultry industry. As a novel strategy for controlling PRMs, vaccine approaches have been focused upon and several candidate vaccine antigens against PRMs have been reported. Tropical (TFM, Ornithonyssus bursa) and northern (NFM, Ornithonyssus sylviarum) fowl mites are also hematophagous and cause poultry industry problems similar to those caused by PRM. Therefore, ideal antigens for anti-PRM vaccines are molecules that cross-react with TFMs and NFMs, producing pesticidal effects similar to those against PRMs. In this study, to investigate the potential feasibility of developing vaccines with broad efficacy across mite species, we identified and characterized cysteine proteases (CPs) of TFMs and NFMs, which were previously reported to be effective vaccine antigens of PRMs. The open reading frames of CPs from TFMs and NFMs had the same sequences, which was 73.0% similar to that of PRMs. Phylogenetic analysis revealed that the CPs of TFMs and NFMs clustered in the same clade as CPs of PRMs. To assess protein functionality, we generated recombinant peptidase domains of CPs (rCP-PDs), revealing all rCP-PDs showed CP-like activities. Importantly, the plasma obtained from chickens immunized with each rCP-PD cross-reacted with rCP-PDs of different mites. Finally, all immune plasma of rCP-PDs reduced the survival rate of PRMs, even when the plasma was collected from chickens immunized with rCP-PDs derived from TFM and NFM. Therefore, CP antigen is a promising, broadly efficacious vaccine candidate against different avian mites.

Acaricidal activity of bioactive compounds isolated from Aspergillus oryzae against poultry red mites, Dermanyssus gallinae (Acari: Dermanyssidae)

Dermanyssus gallinae, the poultry red mite (PRM), is an obligate ectoparasite feeding on poultry blood, seriously affecting the health of layers and egg production. The control of PRMs mainly relies on chemical drugs, which is facing several challenges such as the environment pollution and drug resistance. Using fungal metabolites is an environmentally friendly alternative for the control of pests. However, few studies have been conducted on the efficacy of fungal metabolites against D. gallinae. In this study, five strains of fungi were isolated from D. gallinae under laboratory conditions, and their extracts with ethyl acetate were tested for acaricidal activity on D. gallinae. The crude extract of Aspergillus oryzae caused 75.55 ± 6.94% mortality of mites at a concentration of 12.5 mg/mL, showing the highest acaricidal effect in all extracts. Subsequently, the extract of A. oryzae was isolated by bio-guided fractionation, and ten major compounds were identified by LC-MS/MS analysis. The results of bioassays indicated that five compounds exhibited acaricidal activity against D. gallinae. N, N-dimethyldecylamine N-oxide was the optimal acaricidal compound with LC50 of 0.568 mg/mL. Additionally, palmitic acid, triethanolamine, cuminaldehyde, and 2,4-dimethylbenzaldehyde also showed acaricidal activity. These compounds have great application potential in the mite control, and the analysis of these fungal acaricidal substances provides a new idea and basis for the subsequent development of PRM control technology.

Evaluation of the interaction of citral, geraniol and thymol on the poultry red mite Dermanyssus gallinae (DE GEER, 1778) under in vitro conditions

The control of Dermanyssus gallinae in small productions of laying hens is carried out by using chemical methods. However, its indiscriminate use has generated resistance and environmental pollution problems. This problem has encouraged the use of natural substances to control mites. Thus, the objective of this work was to evaluate the acaricidal activity of the bioactive citral (Ci), geraniol (Ge) and thymol (Thy) on D. gallinae under in vitro conditions using six concentrations (0.05, 1, 2, 3, 4 and 5g/mL). In addition, the interactions of the mixtures of the three bioactive were evaluated through binary (1:1) and tertiary (1:1:1) combinations. The interaction between of the combination of bioactive was performed by using CompuSyn software and calculating the combination index (CI). LC50, LC90, and LC99 with 95% confidence limits were estimated by Probit analysis. The bioactive Ci, Ge and Thy show acaricidal activity on the poultry red mite. The combination of Ge:Thy and Ci:Ge showed very strong synergism with CI of 0.084 and 0.052, whereas Ci:Thy showed strong synergism with CI of 0.122 at a concentration of 0.05g/mL. The tertiary combination in 1:1:1 showed a higher toxic effect and strong synergistic effects at low concentrations with 100% mortality at 1g/mL concentration with a CI of 0.147. The combination of natural bioactive could be an additional way to control D. gallinae without putting the welfare of the birds at risk and would be an environmentally friendly measure.

Profiling of Dermanyssus gallinae genes involved in acaricide resistance

The poultry red mite (PRM), Dermanyssus gallinae, is a major threat for the poultry industry worldwide. Chemical compounds have been extensively used for PRM control, leading to selection of resistant mites. Molecular mechanisms of resistance have been investigated in arthropods, showing the role of target-site insensitivity and enhanced detoxification. Few studies are available about those mechanisms in D. gallinae, and none have yet focused on the expression levels of detoxification enzymes and other defense-related genes through RNA-seq. We tested PRM populations from Italy for their susceptibility to the acaricidal compounds phoxim and cypermethrin. Mutations in the voltage-gated sodium channel (vgsc) and in acetylcholinesterase (AChE) were investigated, detecting mutations known to be associated with acaricide/insecticide resistance in arthropods, including M827I and M918L/T in the vgsc and G119S in the AChE. RNA-seq analysis was performed to characterize metabolic resistance in fully susceptible PRM and in cypermethrin-resistant PRM exposed and unexposed to cypermethrin as well as phoxim resistant PRM exposed and unexposed to phoxim. Detoxification enzymes (including P450 monooxygenases and glutathione-S-transferases), ABC transporters and cuticular proteins were constitutively overexpressed in phoxim and cypermethrin resistant mites. In addition, heat shock proteins were found constitutively and inductively upregulated in phoxim resistant mites, while in cypermethrin resistant mites esterases and an aryl hydrocarbon receptor were constitutively highly expressed. The findings suggest that acaricide resistance in D. gallinae is due to both target-site insensitivity and overexpression of detoxification enzymes and other xenobiotic defense-related genes, which is mostly constitutive and not induced by treatment. Understanding the molecular basis of resistance could be useful to screen or test PRM populations in order to select targeted acaricides and to avoid the abuse/misuse of the few available compounds.

Blood-feeding adaptations and virome assessment of the poultry red mite Dermanyssus gallinae guided by RNA-seq

Dermanyssus gallinae is a blood-feeding mite that parasitises wild birds and farmed poultry. Its remarkably swift processing of blood, together with the capacity to blood-feed during most developmental stages, makes this mite a highly debilitating pest. To identify specific adaptations to digestion of a haemoglobin-rich diet, we constructed and compared transcriptomes from starved and blood-fed stages of the parasite and identified midgut-enriched transcripts. We noted that midgut transcripts encoding cysteine proteases were upregulated with a blood meal. Mapping the full proteolytic apparatus, we noted a reduction in the suite of cysteine proteases, missing homologues for Cathepsin B and C. We have further identified and phylogenetically analysed three distinct transcripts encoding vitellogenins that facilitate the reproductive capacity of the mites. We also fully mapped transcripts for haem biosynthesis and the ferritin-based system of iron storage and inter-tissue trafficking. Additionally, we identified transcripts encoding proteins implicated in immune signalling (Toll and IMD pathways) and activity (defensins and thioester-containing proteins), RNAi, and ion channelling (with targets for commercial acaricides such as Fluralaner, Fipronil, and Ivermectin). Viral sequences were filtered from the Illumina reads and we described, in part, the RNA-virome of D. gallinae with identification of a novel virus, Red mite quaranjavirus 1.