Evaluation of the poultry red mite, Dermanyssus gallinae (Acari: Dermanyssidae) susceptibility to some acaricides in field populations from Italy

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

BACKGROUND

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.

RESULTS

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.

CONCLUSION

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.

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.

Identification and biochemical characterization of a carboxylesterase gene associated with β-cypermethrin resistance in Dermanyssus gallinae

Dermanyssus gallinae is a major hematophagous ectoparasite in layer hens. Although the acaricide β-cypermethrin has been used to control mites worldwide, D. gallinae has developed resistance to this compound. Carboxylesterases (CarEs) are important detoxification enzymes that confer resistance to β-cypermethrin in arthropods. However, CarEs associated with β-cypermethrin resistance in D. gallinae have not yet been functionally characterized. Here, we isolated a CarE gene (Deg-CarE) from D. gallinae and assayed its activity. The results revealed significantly higher expression of Deg-CarE in the β-cypermethrin-resistant strain (RS) than in the susceptible strain (SS) toward α-naphthyl acetate (α-NA) and β-naphthyl acetate (β-NA). These findings suggest that enhanced esterase activities might have contributed to β-cypermethrin resistance in D. gallinae. Quantitative real-time PCR analysis revealed that Deg-CarE expression levels were significantly higher in adults than in other life stages. Although Deg-CarE was upregulated in the RS, significant differences in gene copy numbers were not observed. Additionally, Deg-CarE expression was significantly induced by β-cypermethrin in both the SS and RS. Moreover, silencing Deg-CarE via RNA interference decreased the enzyme activity and increased the susceptibility of the RS to β-cypermethrin, confirming that Deg-CarE is crucial for β-cypermethrin detoxification. Finally, recombinant Deg-CarE (rDeg-CarE) expressed in Escherichia coli displayed high enzymatic activity toward α/β-NA. However, metabolic analysis indicated that rDeg-CarE did not directly metabolize β-cypermethrin. The collective findings indicate that D. gallinae resistance to β-cypermethrin is associated with elevated CarEs protein activity and increased Deg-CarE expression levels. These findings provide insights into the metabolic resistance of D. gallinae and offer scientific guidance for the management and control of D. gallinae.

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.

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.

In Vivo Evaluation of an Ivermectin and Allicin Combination Treatment for Eradicating Poultry Red Mite

A safe and effective method for eradicating poultry red mite (PRM; Dermanyssus gallinae) is urgently needed, as existing treatments show a low efficacy or hazardous effects on chickens. We evaluated the efficacy of a combined treatment with ivermectin and allicin (IA) against PRMs in chickens and drug residues in non-target samples. The efficiency of PRM eradication by IA was compared with those of natural acaricides in vitro. Ivermectin (0.25 mg/mL) + allicin (1 mg/mL) (IA compound) was sprayed on isolator housing hens with PRMs. The PRM mortality rate, clinical symptoms, and ivermectin residue in hens were analyzed. IA showed the highest PRM-eradication efficacy among all tested compounds in vitro. The insecticidal rates of IA were 98.7%, 98.4%, 99.4%, and 99.9% at 7, 14, 21, and 28 days of treatment, respectively. After inoculating PRMs, hypersensitivity, itching, and a pale-colored comb were observed in control animals, which were absent in treated hens. No clinical symptoms from IA and ivermectin residues were found in hens. IA effectively exterminated PRMs, demonstrating its potential for industrial use to treat PRMs.

Management of the poultry red mite Dermanyssus gallinae with physical control methods by inorganic material and future perspectives

Poultry red mite (PRM), the ectoparasitic mite Dermanyssus gallinae found in laying hen farms, is a significant threat to poultry production and human health worldwide. It is a suspected disease vector and attacks hosts' other than chickens, including humans, and its economic importance has increased greatly. Different strategies to control PRM have been widely tested and investigated. In principle, several synthetic pesticides have been applied to control PRM. However, recent alternative control methods to avoid the side effects of pesticides have been introduced, although many remain in the early stage of commercialization. In particular, advances in material science have made various materials more affordable as alternatives for controlling PRM through physical interactions between PRM. This review provides a summary of PRM infestation, and then includes a discussion and comparison of different conventional approaches: 1) organic substances, 2) biological approaches, and 3) physical inorganic material treatment. The advantages of inorganic materials are discussed in detail, including the classification of materials, as well as the physical mechanism-induced effect on PRM. In this review, we also consider the perspective of using several synthetic inorganic materials to suggest novel strategies for improved monitoring and better information regarding treatment interventions.

Potential of ferritin 2 as an antigen for the development of a universal vaccine for avian mites, poultry red mites, tropical fowl mites, and northern fowl mites

Introduction

Poultry red mites (PRMs, Dermanyssus gallinae), blood-sucking ectoparasites, are a threat to the poultry industry because of reduced production caused by infestation. In addition, tropical fowl mites (TFMs, Ornithonyssus bursa) and northern fowl mites (NFMs, Ornithonyssus sylviarum) are hematophagous, distributed in various regions, genetically and morphologically close to PRMs, and cause similar problems to the poultry industry. Vaccine approaches have been studied for PRM control, and several molecules have been identified in PRMs as candidates for effective vaccine antigens. The development of an anti-PRM vaccine as a universal vaccine with broad efficacy against avian mites could improve the productivity of poultry farms worldwide. Molecules that are highly conserved among avian mites and have critical functions in the physiology and growth of mites could be ideal antigen candidates for the development of universal vaccines. Ferritin 2 (FER2), an iron-binding protein, is critical for the reproduction and survival of PRMs and has been reported as a useful vaccine antigen for the control of PRMs and a candidate for the universal vaccine antigen in some tick species.

Method and results

Herein, we identified and characterized FER2 in TFMs and NFM. Compared with the sequence of PRM, the ferroxidase centers of the heavy chain subunits were conserved in FER2 of TFMs and NFMs. Phylogenetic analysis revealed that FER2 belongs to clusters of secretory ferritins of mites and other arthropods. Recombinant FER2 (rFER2) proteins from PRMs, TFMs, and NFMs exhibited iron-binding abilities. Immunization with each rFER2 induced strong antibody responses in chickens, and each immune plasma cross-reacted with rFER2 from different mites. Moreover, mortality rates of PRMs fed with immune plasma against rFER2 from TFMs or NFMs, in addition to PRMs, were higher than those of control plasma.

Discussion

rFER2 from each avian mite exhibited anti-PRM effects. This data suggests that it has the potential to be used as an antigen candidate for a universal vaccine against avian mites. Further studies are needed to access the usefulness of FER2 as a universal vaccine for the control of avian mites.

In Vitro Acaricidal Activity of Silver Nanoparticles (AgNPs) against the Poultry Red Mite (Dermanyssus gallinae)

Dermanyssus gallinae (PRM) is the most common blood-sucking ectoparasite in laying hens and is resistant against numerous acaricides. Silver nanoparticles (AgNPs) represent an innovative solution against PRM. The current study aimed to assess the in vitro acaricidal activity of AgNPs against PRM and describe their potential mechanism of action. Nanoparticles were produced using a wet chemistry approach. Mites were collected using AviVet traps from 18 poultry farms in Greece. Contact toxicity bioassays were carried out for 24 h with negative controls, 20, 40, 60, or 80 ppm AgNPs. Analysis of variance was used to compare the mortality rates of PRM between the control and treatment groups, while LC₅₀, LC₉₀, and LC₉₉ values were estimated using probit regression analysis for the total farms jointly and separately. Nanoparticles displayed strong acaricidal activity, and mortality rates were significantly different between groups and increased by AgNPs concentration. Overall mean LC₅₀, LC₉₀, and LC₉₉ values were 26.5, 58.8, and 112.3 ppm, respectively. Scanning electron microscopy on mites treated with 80 ppm AgNPs revealed cracks in their exoskeleton and limb detachments, presumably resulting from the interaction between AgNPs and the mites' chitin. Future studies should focus on assessing AgNPs residues in chicken tissues before moving into field trials.

Suppressive modulation of host immune responses by Dermanyssus gallinae infestation

The poultry red mite (Dermanyssus gallinae, PRM) is a blood-sucking ectoparasite in chickens and is one of the most serious threats to poultry farms. Mass infestation with PRMs causes various health problems in chickens, resulting in significant productivity reduction in the poultry industry. Infestation with hematophagous ectoparasites, such as ticks, induces host inflammatory and hemostatic reactions. On the other hand, several studies have reported that hematophagous ectoparasites secrete various immunosuppressants from their saliva to suppress host immune responses to maintain blood sucking. Here, we examined the expression of cytokines in peripheral blood cells to investigate whether PRM infestation affects immunological states in chickens. In PRM-infested chickens, anti-inflammatory cytokines, IL-10 and TGF-β1, and immune checkpoint molecules, CTLA-4 and PD-1, were highly expressed compared to noninfested chickens. PRM-derived soluble mite extracts (SME) upregulated the gene expression of IL-10 in peripheral blood cells and HD-11 chicken macrophages. In addition, SME suppressed the expression of interferons and inflammatory cytokines in HD-11 chicken macrophages. Moreover, SME induces the polarization of macrophages into anti-inflammatory phenotypes. Collectively, PRM infestation could affect host immune responses, especially suppress the inflammatory responses. Further studies are warranted to fully understand the influence of PRM infestation on host immunity.

Genetic Characterization of the Poultry Red Mite (Dermanyssus gallinae) in Poland and a Comparison with European and Asian Isolates

(1) Background: The blood-feeding mite Dermanyssus gallinae (De Geer 1778) continues to attract wide interest from researchers and bird breeders. The aim of this study was to evaluate the genetic diversity of D. gallinae populations in five commercial laying hen farms in Poland and to determine their similarity with isolates from other countries. The study involved an analysis of a fragment of the cytochrome c oxidase subunit I gene (COI). A total of 38 isolates obtained from Polish farms and 338 sequences deposited in GenBank were analyzed. (2) Results: Haplotype No. 46 was dominant (90%) in Polish isolates and was homologous with the isolates from Great Britain, the Netherlands, Belgium, Japan, and South Korea. These results are indicative of high genetic homogeneity and common ancestry of the poultry red mite and point to a common source of infestation in the examined farms. (3) Conclusions: The genetic diversity of D. gallinae should be further studied to promote a better understanding of how this parasite is disseminated within and between countries.

Lithium Chloride Shows Effectiveness against the Poultry Red Mite (Dermanyssus gallinae)

The poultry red mite (Dermanyssus gallinae) is the main pest of poultry, causing severe problems by being a vector of several animal and human pathogens. The number of miticides is few, and their efficacy in practice implies problems of residues and resistance; therefore, the demand for a new and safe agent is constant. The present publication investigated the effectiveness of lithium chloride under in vitro conditions on poultry red mites. This chemical currently appears to be one of the most promising alternatives to study amongst potential applicants to treat varroosis, a fatal disease of honey bees. In Experiment I, the previously used experimental doses (5.52 M, 2.76 M, 1.38 M) on Varroa mites confirmed their in vitro activity on the poultry red mite. Three event times (uncontrolled movement, immobilisation and death) were recorded to base the response to treatment for each concentration. In Experiment II, the LD 50 value was calculated, i.e., the value at which 50% of the mites were killed by the treatment. This Experiment showed that the LD50 of lithium chloride = 0.265 M in the poultry red mite. It is to note that the study remained restricted to in vitro confirmation of lithium chloride's effectiveness on the parasite. Thus, further extensive studies are needed to decide whether it has any relevance in practice against D. gallinae, and also to assess potential residue problems that could affect poultry products.

Evaluation of the in vitro acaricidal activity of Chinese herbal compounds on the poultry red mite (Dermanyssus gallinae)

The poultry red mite Dermanyssus gallinae is an economically important pest in poultry farms worldwide, but an effective treatment option is lacking. The current study determined the effectiveness of six Chinese herbal medicines [Syzygium aromaticum (clove), Hibiscus syriacus (Hibiscus), Illicium verum (star anise), Leonurus artemisia (motherwort), Cinnamomum cassia (cinnamon), and Taraxacum sp. (dandelion)] against D. gallinae. Alcohol extracts were prepared via the solvent extraction method and the phenol, flavonoid, and tannin contents were determined. These active components were highest in S. aromaticum and lowest in H. syriacus, I. verum. No tannin content was detected in L. artemisia. All extracts showed contact toxicity against D. gallinae at a test concentration of 1 g/mL, with S. aromaticum and L. artemisia resulting in 100% mortality. S. aromaticum, L. artemisia, and I. verum showed the best efficacy (LC₅₀ 0.159, 0.200, and 0.292 g/mL, respectively). Different combinations of extracts showed an additive effect of I. verum LC₉₀ + L. artemisia LC₉₀. The acaricidal efficacy of this combination was tested against different developmental stages of D. gallinae, being most efficacious against nymphal and larval D. gallinae, with a corrected mortality rate of 100%. However, inhibition of egg hatching was only 53.69%. Taken together, these results highlight I. verum LC₉₀ + L. artemisia LC₉₀ as a promising compound with severe contact toxicity against D. gallinae. Given the wide cultivation of these species and their extensive use in foodstuffs and cosmetics as flavors and fragrances, they could be a cheap, readily available ecofriendly alternative to pesticides currently used in poultry farms.

Evaluation of the Acaricidal Effectiveness of Fipronil and Phoxim in Field Populations of Dermanyssus gallinae (De Geer, 1778) from Ornamental Poultry Farms in Italy

The poultry red mite Dermanyssus gallinae is the most important blood-sucking ectoparasite in egg-laying hen facilities. The aim of this study was to evaluate the in vitro acaricidal activity of different concentration of authorized (phoxim, ByeMite®, 500 mg/mL) and unauthorized (fipronil, Frontline® 250 mg/100 mL spray) molecules on 14 field isolates of D. gallinae collected from different ornamental poultry farms from different Italian regions. The sensitivity test was performed by contact exposure to four concentrations of each insecticide diluted at 1:5 (10,000-2000-400-80 ppm for phoxim, 500-100-20-4 ppm for fipronil) on a filter paper. The effectiveness of the treatment was significantly (p < 0.0001) associated with the dose of the pesticide used. Considering the mean lethality, phoxim has greater efficacy compared to fipronil (p < 0.001). A great variability of lethality rate was observed with the increase in fipronil dilution; conversely, for phoxim, some outliers were observed, particularly in one farm, suggesting the hypothesis that a certain degree of resistance in the mite population could occur possibly as a consequence of the continual contact with the molecule. This underlines the importance of the use of licensed products administered at correct dosages and the need for alternative molecules to avoid the onset of drug resistance phenomena.

Evaluation of the in vitro acaricidal activity of ethanol extracts of seven Chinese medicinal herbs on Ornithonyssus sylviarum (Acari: Macronyssidae)

Ornithonyssus sylviarum (Acari: Macronyssidae) is a common ectoparasite that feeds on the blood of poultry. Following infestation, this mite will cause symptoms such as weight loss, anemia, and decreased egg production. To explore green and safe drugs for the prevention and treatment of O. sylviarum, this study evaluated the effects of ethanol extracts of seven Chinese medicinal herbs-Leonurus artemisia (motherwort), Illicium verum (star anise), Cinnamomum cassia (cinnamon), Hibiscus syriacus, Artemisia argyi (Chinese mugwort), Taraxacum sp. (dandelion), and Syzygium aromaticum (clove)-on O. sylviarum at different life stages. The results showed that different methods of administration affected the acaricidal efficacy of these plant extracts on O. sylviarum. After 6 h of administration with the fumigation method, the acaricidal efficacy of S. aromaticum on adults, nymphs and larvae of O. sylviarum reached 100%. 30 min after administration with the infiltration method, S. aromaticum, H. syriacus and L. artemisia showed acaricidal effects on adults and nymphs of O. sylviarum reaching 100%. In another experiment evaluating the inhibition of egg hatching of O. sylviarum with alcohol extracts of these seven herbs, at 48 h after treatment, A. argyi and C. cassia showed inhibition rates of 19.4%. The results of this study indicate that S. aromaticum induced mortality at all stages of O. sylviarum, whereas A. argyi was found to be the most effective at inhibiting the mite's egg hatching among the seven herbs. These herbs can therefore be used as potential substitutes for chemical pesticides to prevent and control O. sylviarum. These results provide practical knowledge for the control of O. sylviarum.

In vitro evaluation of the response of Dermanyssus gallinae to products in aqueous suspension

The hematophagous mite Dermanyssus gallinae poses a serious sanitary problem in the Brazilian laying poultry industry. Its control is typically performed with acaricides, either in powder or liquid form. However, the intensive use of these products has caused populations of this species to develop tolerance and even resistance. The aim of the present study is to evaluate the response of eggs and adults of D. gallinae to products in aqueous suspension according to commercial indication and as per the recommendations of the Brazilian Ministry of Agriculture, Livestock and Supply. The study used four acaricide products (product 1: cypermethrin, chlorpyrifos, and piperonyl butoxide; product 2: alkyl-benzyl-dimethyl ammonium chloride, glutaraldehyde, deltamethrin; product 3: dichlorvos; product 4: fluralaner) tested in vitro using the contact method. Distilled water was used in the control group. The effectiveness of each of the products differed significantly between eggs and adults. Products 2, 3, and 4 caused 100% of adult mortality up to day 5 after start of treatment, product 1 97.5%. The corrected mortality (non-viability) of eggs was 21.4% (product 1) 39.4% (product 2), 47.8% (product 3), and 14.4% (product 4). Although the products evaluated were effective against adults of D. gallinae, their effectiveness against eggs was lower under the same conditions. This finding might be directly related to frequent D. gallinae reinfestations in poultry houses.

An in vitro evaluation of the sensitivity and responses of Dermanyssus gallinae to selected acaricides

Dermanyssus gallinae is an obligatory ectoparasite of birds which feeds on blood and significantly compromise the well-being of commercially raised laying hens. In this study, the mortality rates and responses of D. gallinae to 2 acaricides with a physical mode of action (Dergall and Mite Max) and 2 acaricides with a chemical mode of action (Milben Ex and Bio PK) were evaluated in tree dilutions (S1–3) and compared at 8-time intervals after application. The evaluation involved a novel method that simulates real-world conditions in a commercial poultry farm. Tested products have shown high efficacy (84.3–100%) against D. gallinae in the producer recommended solution (S1). Acaricides with a physical mechanism of action were as effective as chemical agents in eradicating poultry red mites. The compared preparations differed only in the onset of action which was longer in acaricides with a physical mode of action (1–6 h for chemical 24 h for physical in S1). An increase in the concentration of the active ingredient did not significantly speed up the onset of action of the evaluated preparations. However, the efficacy of Dergall and Bio PK decreased when the applied dose was halved, to 12% and 0% respectively. A decrease in the dose Mite Max led to a somewhat smaller, but not statistically significant decrease in mite mortality rates (74%). The proposed method for evaluating acaricide efficacy can be helpful in selecting the most effective preparations and the optimal concentration of the working solution to be applied in commercial layer farms, thus reducing the costs associated with the eradication of D. gallinae. The developed method enables a reliable evaluation of acaricides with both a physical and chemical mode of action, and it supports observations of the parasites’ responses to the applied treatment.

Entomopathogenic Fungi and Bacteria in a Veterinary Perspective

Simple Summary

Several fungal species are well suited to control arthropods, being able to cause epizootic infection among them and most of them infect their host by direct penetration through the arthropod’s tegument. Most of organisms are related to the biological control of crop pests, but, more recently, have been applied to combat some livestock ectoparasites. Among the entomopathogenic bacteria, Bacillus thuringiensis, innocuous for humans, animals, and plants and isolated from different environments, showed the most relevant activity against arthropods. Its entomopathogenic property is related to the production of highly biodegradable proteins. Entomopathogenic fungi and bacteria are usually employed against agricultural pests, and some studies have focused on their use to control animal arthropods. However, risks of infections in animals and humans are possible; thus, further studies about their activity are necessary.

Abstract

The present study aimed to review the papers dealing with the biological activity of fungi and bacteria against some mites and ticks of veterinary interest. In particular, the attention was turned to the research regarding acarid species, Dermanyssus gallinae and Psoroptes sp., which are the cause of severe threat in farm animals and, regarding ticks, also pets. Their impact on animal and human health has been stressed, examining the weaknesses and strengths of conventional treatments. Bacillus thuringiensis, Beauveria bassiana and Metarhizium anisopliae are the most widely employed agents. Their activities have been reviewed, considering the feasibility of an in-field application and the effectiveness of the administration alone or combined with conventional and alternative drugs is reported.

Fumigant activity of essential oils from Cinnamomum and Citrus spp. and pure compounds against Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae) and toxicity toward the nontarget organism Beauveria bassiana (Vuill.)

Dermanyssus gallinae(De Geer) (Acari: Dermanyssidae) is the main ectoparasite associated with laying poultry. This mite is commonly controlled by the application of synthetic chemical insecticides, wich lead to the selection of resistant populations and formation of residues in eggs. Thus, new molecules must be developed to control D. gallinae. This work evaluated the toxicity of essential oils (EOs) from Cinnamomum cassia, Cinnamomum camphora, Cinnamomum camphora var. linalooliferum, Citrus aurantium, Citrus aurantium var. bergamia, Citrus aurantifolia and Citrus reticulata var. tangerine against D. gallinae. Additionally, the chemical profiles of the most bioactive EOs were analyzed by gas chromatography coupled with mass spectrometry (GC-MS) and the major compounds were subjected to new tests using D. gallinae. The most toxic EOs against D. gallinae were evaluated for the nontarget entomopathogenic fungus Beauveria bassiana (Unioeste 88). The EOs from C. cassia (LC₅₀ = 25.43 ± 1.0423 μg/cm³) and C. camphora var. linalooliferum (LC₅₀ = 39.84 ± 1.9635 μg/cm³) were the most active in the fumigant bioassay and caused mortality rates of 96 and 61%, respectively. The GC-MS analysis revealed that the major constituents of EOs from C. cassia and C. camphora var. linalooliferum were trans-cinnamaldehyde and linalool, respectively. The pure compounds, trans-cinnamaldehyde (LC₅₀ = 68.89 ± 3.1391 μg/cm³) and linalool (LC₅₀ = 51.45 ± 1.1967 μg/cm³), were tested on D. gallinae and showed lower toxicity than the EOs. Thus, the compounds were not the only active substances produced by C. cassia and C. camphora var. linalooliferum; moreover synergism may have occurred between the substances. The EOs from C. cassia and C. camphora var. linalooliferum were also toxic to B. bassiana (Unioeste 88). Thus, EOs from C. cassia and C. camphora var. linalooliferum are promising candidates for use in D. gallinae control, but cannot be used in conjunction with the fungus B. bassiana.

Susceptibility of Dermanyssus gallinae from China to acaricides and functional analysis of glutathione S-transferases associated with beta-cypermethrin resistance

Dermanyssus gallinae poses a significant threat to poultry production, and the resistance to pyrethroids has been identified worldwide. Periodic monitoring of acaricide resistance in D. gallinae is very important for its control, and molecular mechanism associated with beta-cypermethrin resistance in D. gallinae is not fully clear. Results showed, four field isolates of CBP-1, CBP-2, CBP-5 and CBY-1 from China remained either susceptible or with decreased susceptibility (resistance ratio < 5.0) to phoxim, amitraz, propoxur and carbaryl. Four field isolates of CBP-1, CBP-3, CBY-2 and CBH-1 had developed high or extremely high level of resistance (resistance ratio ≥ 40.0) to beta-cypermethrin or permethrin. Detoxification enzyme activity of GSTs was significantly higher in beta-cypermethrin resistant (RS) than susceptible strain (SS), indicating that GSTs are probably involved in beta-cypermethrin resistance in D. gallinae. The recombinant GSTs (rGST-1, 2, 3) showed a pronounced activity toward the conjugates of 1-chloro-2, 4 dinitrobenzene (CDNB) and glutathione (GSH), with rGST-1 presenting the highest enzymatic activity. Constitutive over-expression of Deg-GST-2 was detected in RS strain, and GSTs genes were all inducible with the treatment of beta-cypermethrin in SS and RS strains. More importantly, knocking down Deg-GST-2 gene expression by RNAi increased the susceptibility of RS strain to beta-cypermethrin. HPLC analysis indicated that rGST-1 protein could metabolize phoxim directly, but rGSTs could not directly metabolize beta-cypermethrin. Our results indicated that some field isolates of D. gallinae from China had developed high level of resistance to pyrethroids, and elevated GSTs activity as well as increased GSTs expression levels were involved in beta-cypermethrin resistance, but the three evaluated GSTs did not play a direct role in the metabolism of beta-cypermethrin.

Dermanyssus gallinae and chicken egg production: impact, management, and a predicted compatibility matrix for integrated approaches

The poultry red mite, Dermanyssus gallinae, is a worldwide threat to egg production and animal and human welfare. This mite is also a potential vector for several significant diseases. EU regulation that forbids the use of conventional cages for egg-laying hens may favour the growth of D. gallinae, a species known to thrive in more complex housing systems. Current control measures emphasize the use of chemical acaricides, which may have limited efficacy on D. gallinae considering its temporary blood-feeding behaviour. In integrated pest management (IPM), two or more compatible measures targeting physical, environmental, and/or biological aspects could be judiciously combined to enhance the effectiveness against D. gallinae infestation. To inform current and future IPM for D. gallinae, a compatibility matrix is proposed to guide the selection of control measures for field application.

Effects of heating laying hen houses between consecutive laying cycles on the survival of the poultry red mite Dermanyssus gallinae

The poultry red mite (PRM) Dermanyssus gallinae, the most common ectoparasite affecting laying hens worldwide, is difficult to control. During the period between consecutive laying cycles, when no hens are present in the layer house, the PRM population can be reduced drastically. Heating a layer house to temperatures above 45 °C for several days in order to kill PRM has been applied in Europe. The effect of such a heat treatment on the survival of PRM adults, nymphs and eggs, however, is largely unknown. To determine that effect, an experiment was executed in four layer houses. Nylon bags with ten PRM adults, nymphs or eggs were placed at five different locations, being a) inside the nest boxes, b) between two wooden boards, to simulate refugia, c) near an air inlet, d) on the floor, under approximately 1 cm of manure and e) on the floor without manure. Mite survival was measured in 6 replicates of each of these locations in each of four layer houses. After heating up the layer house, in this case with a wood pellet burning heater, the temperature of the layer house was maintained at ≥ 45 °C for at least 48 h. Thereafter, the bags were collected and the mites were assessed as being dead or alive. The eggs were assessed for hatchability. Despite a maximum temperature of only 44 °C being reached at one location, near an air inlet, all stages of PRM were dead after the heat treatment. It can be concluded that a heat treatment of layer houses between consecutive laying cycles appears to be an effective method to control PRM.

Evaluation of the vaccine efficacy of three digestive protease antigens from Dermanyssus gallinae using an in vivo rearing system

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite considered as the major pest in the egg-laying industry. Vaccination is feasible strategy for controlling the haematophagous PRMs. Cathepsin D (CatD), cathepsin L (CatL) and legumain (Lgm) are three endopeptidases participating in digestion of hemoglobin in ticks. The in vitro test and the on-hen feeding device have been used to evaluate the efficacy of vaccines against D. gallinae, however they lacked some of the natural feeding cues for mites, resulting in unreliable results. In the present study, a reliable in vivo rearing system which was nearly close to the natural infestation status of mites was applied to evaluate the efficacy of vaccines against D. gallinae. After vaccinations with rDg-CatD-1, rDg-CatL-1 or rDg-Lgm, chicks developed the antigen-specific IgY immune response to each antigen. The survival rates of D. gallinae in three groups decreased significantly after they fed on the immunized birds. And the oviposition rate and fecundity were significantly reduced by 13.18% and 49.90% in the rDg-CatD-1 immunized group, 5.49% and 38.55% in the rDg-CatL-1 immunized group, respectively. Moreover, immunization with rDg-CatD-1 or rDg-CatL-1 significantly decreased the blood digestion rate of D. gallinae. However, no statistically significant effects on reproduction performance and blood digestion rate of mite were observed in group immunized with rDg-Lgm. Our results demonstrated that immunization with rDg-CatD-1 or rDg-CatL-1 could prevent and control D. gallinae by reducing the survival, reproductive capacity and blood digestion of mite. Importantly, the evaluation system based on the in vivo rearing system was reliable and practical, and it can accurately evaluate the effects of immunization on D. gallinae for pre-screening of potential novel antigens.

Molecular and biochemical characterization of enolase from Dermanyssus gallinae

Enolase, a multifunctional glycolytic enzyme, is known to act as a plasminogen receptor in many species, involved in the pivotal processes such as motility, adhesion, invasion, growth, and differentiation of the parasites. Knowledge on the function of enolase from Dermanyssus gallinae is very limited. Here we report on the molecular cloning, enzymatic activity, tissue distribution and plasminogen binding activity of enolase from D. gallinae (DgENO). The full-length of cDNA was 1305 bp, specifying a peptide of 434 amino acids. Bioinformatics analysis showed that DgENO was highly conserved compared with a range of organisms, indicating the potentially similar functions in D. gallinae. A recombinant DgENO (rDgENO) protein was produced and characterized, it catalyzed the dehydration of 2-phospho-D-glycerate to phosphoenolpyruvate, the optimal pH was 7.5. Polyclonal antibodies were generated in mice and western blotting indicated that antiserum specifically recognized the native enolase in the somatic extracts from D. gallinae. Immunohistochemical staining of mite sections revealed that the distribution of DgENO was ubiquitous with high level in salivary gland, mite digestive tissues and fat bodies in D. gallinae. Expression level of DgENO was observed mostly in engorged adult mites. Moreover, ELISA binding assay showed that rDgENO could bind plasminogen, and lysine analog ε-aminocaproic acid significantly inhibited this binding activity, indicating that D. gallinae enolase is a receptor of plasminogen. The present study provided foundation for understanding of the biological functions of DgENO and its application in development of vaccines against D. gallinae.

Association of mechanical cleaning and a liquid preparation of diatomaceous earth in the management of poultry red mite, Dermanyssus gallinae (Mesostigmata: Dermanyssidae)

The poultry red mite (PRM), Dermanyssus gallinae, is an ectoparasite of great importance related to poultry farms worldwide. Problems associated with its control have led to the search for alternative treatments, especially using inert dust, which has recently been introduced into liquid formulations. Therefore, the objective of this work was to evaluate the acaricidal activity of a liquid diatomaceous earth (DE) preparation in the laboratory and its association with mechanical cleaning (brushing) in the field. In the laboratory it was first determined that a concentration of 10% DE would be necessary for field applications. The field experiment was conducted in a commercial poultry house. The 10% DE liquid preparation was administered in three applications and associated to mechanical cleaning. Then, 42 days after the first DE application, a population reduction of 94.7% was observed in relation to the initial population of mites. These results confirm the efficiency of DE applications in association with mechanical cleaning already adopted in poultry houses as an alternative for the control of D. gallinae, which can also contribute to avoiding mite resistance to chemical acaricides.

Transcription profiling and characterization of Dermanyssus gallinae cytochrome P450 genes involved in beta-cypermethrin resistance

The poultry red mite, Dermanyssus gallinae, poses a significant threat to hen health and poultry husbandry. D. gallinae has typically been controlled using synthetic acaricides, like pyrethroids, but increased resistance to pyrethroids has been found in poultry red mite populations worldwide. Pyrethroids resistance in arthropods has been associated to cytochrome P450 monooxygenases (P450s), a main member of a group of detoxification enzymes. To explore the potential contribution of P450s to the resistance to pyrethroids in D. gallinae, we first identified and then characterized four P450s genes. Phylogenetic analysis revealed that the four P450s genes in D. gallinae belong to three different clades, with two in the CYP-6, one in the CYP-4 and one in the CYP-2. All four P450s genes were expressed in a similar pattern in D. gallinae at different stages of development, and showed high expression in the adult stage, indicating that they played a role in mite development. Simultaneously, constitutive over-expression of Deg-CYP-3, a clade associated with pesticide metabolism, was detected in a resistant strain (RS) compared with a susceptible strain (SS). When exposed to beta-cypermethrin, the four P450s gene transcripts in the RS strain increased in a time-dependent manner. In particular, Deg-CYP-3 expression increased 5-fold compared to gene expression in control group at 12 h, although the four P450s genes were not induced in the SS strain. Our results show the first insights into the molecular characteristics of P450s genes in D. gallinae. The elevated presence of P450s genes in the RS strain, indicated by their constitutive over-expression and their inducible expression, suggests that they confer resistance to beta-cypermethrin, and are involved in its detoxification.

Control of Dermanyssus gallinae (De Geer 1778) and other mites with volatile organic compounds, a review

Dermanyssus gallinae (De Geer 1778), commonly named the poultry red mite (PRM), is considered to be the most harmful ectoparasite in poultry farms in Europe. This species feeds on the blood of laying hens, but spends most of its time hidden in cracks and crevices around hen nests. To control PRM populations in poultry houses, chemical pesticides are currently used; however, concern is growing regarding the harmful residues found in eggs and hens, along with the increased resistance of mites against several compounds. Alternatives to synthetic compounds are now being explored, including vaccines, biological control, physical control and semiochemical control based on the chemical ecology of PRM. This review focused on the different volatile organic compounds (VOCs) identified from D. gallinae and other mite species that have been discovered to control them. Pheromones (aggregation pheromone, sex pheromone and alarm pheromone) and kairomones promoting attraction behaviour in D. gallinae and other mite species are presented, while VOCs from essential oils and plant extracts with repellent properties are also explored. Finally, devices using VOCs on PRM in the field are described, with devices that have been tested on other Acari species being mentioned as potential directions for the future control of PRM.

Application of carbon dioxide as a novel approach to eradicate poultry red mites

Poultry red mites (PRMs), Dermanyssus gallinae, are one of the most harmful ectoparasites of laying hens. Because of their public health impact, safe, effective methods to eradicate PRMs are greatly needed. Carbon dioxide (CO₂) was shown to eradicate phytophagous mites; however, there is no evidence that PRMs can be eradicated by CO₂. Thus, the efficacy of CO₂, applied by direct-spraying and dry ice-generated exposure, for eradicating PRMs was investigated. Both treatments eradicated > 85% of PRMs within 24 h and 100% of PRMs by 120 h of post-treatment. Therefore, these novel approaches may be useful for eradicating PRMs in clinical settings.

Use of afoxolaner for the treatment of lice (Goniodes pavonis) in different genera (Chrysolophus spp, Lophura spp, Phasianus spp, and Syrmaticus spp) and species of pheasants and West Mexican Chachalacas (Ortalis poliocephala)

Lice are ectoparasites capable of affecting birds, and can result in direct and indirect damage to their host. Afoxolaner is an isoxazoline that has been shown to be effective against these ectoparasites without known adverse effects. The objective of this research was to evaluate the effect of afoxolaner on lice in pheasants and plain chachalacas. A total of 29 pheasants of different genera and species (Chrysolophus pictus, C. amherstiae, Lophura swinghoii, L. nycthemera, Phasianus colchicus, and Syrmaticus reevesii) and 18 West Mexican Chachalacas (Ortalis poliocephala) naturally infested with Goniodes pavonis were used. The birds were allocated to one of two groups: group 1 treated with 2.50 mg/kg of afoxolaner, and group 2 given no treatment. Ectoparasites were collected using the adhesive tape technique and identified. Afoxolaner was administered later as a single dose to group 1, and the clinical assessment to detect ectoparasites was repeated 28 days post-treatment. On day 28 post-treatment, group 1 was found to be negative for the presence of lice. The body weights were compared at the beginning and end of the clinical assessment in both groups and a significant difference in weight of treated birds was found. The mean body weight decreased by 0.017 g in control group, whereas it increased by 0.016 g in treated group. Oral administration of afoxolaner is an effective option for the treatment of Goniodes pavonis infestations in zoo birds.

Acaricidal activity, mode of action, and persistent efficacy of selected essential oils on the poultry red mite (Dermanyssus gallinae)

In this work, the essential oils (EOs) from Litchi chinensis, Clausena anisata, Heracleum sphondylium, Pimpinella anisum, Lippia alba, Crithmum maritimum and Syzygium aromaticum were tested for their contact toxicity against the poultry red mite, Dermanyssus gallinae, a deleterious ectoparasite of aviary systems. In addition, in order to give insights on their mode of action and effectiveness, the vapor phase and residual toxicity tests were also performed. Results showed that amongst all the tested EOs, that of S. aromaticum demonstrated the highest contact toxicity, with a LC₅₀ value of 8.9 μg/mL, followed by C. maritimum and L. chinensis EOs, with LC₅₀ values of 23.7 and 24.7 μg/mL, respectively. L. chinensis and C. anisata EOs showed higher vapor toxicity than the other EOs. L. chinensis and S. aromaticum EOs showed promising toxic effects up to 4 days post-application. Taken together, these results highlighted L. chinensis and S. aromaticum as two promising sources of biopesticides, able to cause severe contact, vapor and residual toxicity in the poultry red mites. Given the wide plant cultivation and uses in foodstuffs, cosmetics, flavour and fragrances, these EOs may be considered cheap and ready-to-use products as valid, eco-friendly alternatives to pesticides currently used in the aviary systems.

Identification and geographical distribution of pyrethroid resistance mutations in the poultry red mite Dermanyssus gallinae

BACKGROUND

The poultry red mite (PRM) Dermanyssus gallinae is the most common ectoparasite on poultry and causes high economic losses in poultry farming worldwide. Pyrethroid acaricides have been widely used for its control and, consequently, pyrethroid resistance has arisen. In this study we aim to investigate the occurrence of resistance and study the geographical distribution of pyrethroid resistance mutations across PRM populations in Europe.

RESULTS

Full dose-response contact bioassays revealed very high levels of resistance against several pyrethroids (α-cypermethrin, fluvalinate, and cyfluthrin) in two PRM populations from Greece, compared to a susceptible reference strain. Resistance was associated with mutations in the gene encoding the target site of pyrethroids, the voltage-gated sodium channel (VGSC). Mutations, M918L and L925V in domain IIS4-S5 and F1534L in domain IIIS6, were found at positions known to play a role in pyrethroid resistance in other arthropod species. Subsequent screening by sequencing VGSC gene fragments IIS4-S5 and IIIS6 revealed the presence and distribution of these mutations in many European populations. In some populations, we identified additional or different mutations including M918V/T, L925M, T929I, I936F, and F1538L. The latter mutation is a possible alternative for F1538I that has been previously associated with pyrethroid resistance in other Acari species.

CONCLUSION

We report very high levels of pyrethroid resistance in PRM populations from Greece, as well as the identification and geographical distribution of 10 pyrethroid resistance mutations in PRM populations across Europe. Our results draw attention to the need for an evidence-based implementation of PRM control, taking acaricide resistance management into consideration. © 2019 Society of Chemical Industry.

A vaccinology Approach to the Identification and Characterization of Dermanyssus Gallinae Candidate Protective Antigens for the Control of Poultry Red Mite Infestations

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite considered as the major pest in the egg-laying industry. Its pesticide-based control is only partially successful and requires the development of new control interventions such as vaccines. In this study, we follow a vaccinology approach to identify PRM candidate protective antigens. Based on proteomic data from fed and unfed nymph and adult mites, we selected a novel PRM protein, calumenin (Deg-CALU), which is tested as a vaccine candidate on an on-hen trial. Rhipicephalus microplus Subolesin (Rhm-SUB) was chosen as a positive control. Deg-CALU and Rhm-SUB reduced the mite oviposition by 35 and 44%, respectively. These results support Deg-CALU and Rhm-SUB as candidate protective antigens for the PRM control.

A survey of free-range egg farmers in the United Kingdom: Knowledge, attitudes and practices surrounding antimicrobial use and resistance

Antimicrobial resistance (AMR) is a significant global challenge affecting human health and attention has been drawn to practices of all stakeholders involved in antimicrobial prescription and administration, including in the livestock sector. This survey of free-range egg farmers (n = 117) was conducted to investigate knowledge, attitudes and practices surrounding antimicrobial use, and identify farmer-led solutions towards responsible antimicrobial use. Most participants proved knowledgeable of AMR and selected treatments based on principles of responsible medicine use. 'Worms' and 'infectious diseases' were the most common reasons for medicine use. Farms with a higher number of poultry houses, younger flock ages at depopulation and farms visited by a vet less than once a year or 3-4 times a year (compared to annually or twice a year) were more likely to select 'ANTIBIOTICS ONLY', as opposed to 'BOTH ANTIBIOTICS AND ANTIPARASITICS' or 'ANTIPARASITICS ONLY' as their most frequently used medicines. Participants from farms with a younger flock age at depopulation, from company-owned farms, and participants purchasing medicines from agricultural merchants instead of veterinary practices were less likely to be taking measures to reduce or replace antimicrobial use. Participants from larger farms and those that had less contact with their vet were less likely to think that they could reduce or replace the amount of antibiotics used. Survey results provided evidence for the important role of veterinarians in guiding antimicrobial stewardship through engagement, collaboration and education. Discussion groups in which farmers share best practices could assist the free-range egg industry in further promoting responsible antimicrobial use.

Reduction in Oviposition of Poultry Red Mite (Dermanyssus gallinae) in Hens Vaccinated with Recombinant Akirin

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite of birds with worldwide distribution that causes economic losses in the egg-production sector of the poultry industry. Traditional control methods, mainly based on acaricides, have been only partially successful, and new vaccine-based interventions are required for the control of PRM. Vaccination with insect Akirin (AKR) and its homolog in ticks, Subolesin (SUB), have shown protective efficacy for the control of ectoparasite infestations and pathogen infection/transmission. The aim of this study was the identification of the akr gene from D. gallinae (Deg-akr), the production of the recombinant Deg-AKR protein, and evaluation of its efficacy as a vaccine candidate for the control of PRM. The anti-Deg-AKR serum IgY antibodies in hen sera and egg yolk were higher in vaccinated than control animals throughout the experiment. The results demonstrated the efficacy of the vaccination with Deg-AKR for the control of PRM by reducing mite oviposition by 42% following feeding on vaccinated hens. A negative correlation between the levels of serum anti-Deg-AKR IgY and mite oviposition was obtained. These results support Deg-AKR as a candidate protective antigen for the control of PRM population growth.

Efficacy of λ-cyhalothrin, amitraz, and phoxim against the poultry red mite Dermanyssus gallinae De Geer, 1778 (Mesostigmata: Dermanyssidae): an eight-year survey

Dermanyssus gallinae (De Geer, 1778) is a major problem for the poultry industry worldwide, as it negatively affects virtually all kinds of rearing systems. Therefore, the control of infestation has become a routine process, and its economic cost is constantly increasing. Until now, most of the control strategies have relied on the use of synthetic chemical drugs, but their efficacy is often questioned by the emergence and diffusion of resistant mite populations. With this in mind, the efficacy of λ-cyhalothrin, amitraz, and phoxim has been verified by testing them against 86 mite populations collected from the same number of poultry farms in Italy from 2008 to 2015. Assays were performed according to the filter paper method using the recommended, half, quarter, double and quadruple doses. The results showed that phoxim and amitraz were the most effective acaricides (median efficacies 80.35% and 80.83%, respectively), but amitraz exhibited a sharp fall in its efficacy during 2011 and 2012, while phoxim maintained its high effectiveness up to 2015, when it dropped. The overall median efficacy of λ-cyhalothrin was 58.33%. The data also highlighted the importance of the use of the right concentration, as an increase in dosage was not always useful against resistant populations, while its reduction also diminished efficacy, simultaneously increasing the risk for the development of resistance.

Acaricidal efficacy of orally administered macrocyclic lactones against poultry red mites (Dermanyssus gallinae) on chicks and their impacts on mite reproduction and blood-meal digestion

Background

The poultry red mite (PRM), Dermanyssus gallinae, is one of the most economically deleterious threats to laying-hen industry worldwide. Macrocyclic lactones (MLs) have been widely used in control of mites in mammals, but the effects of MLs on PRMs are not well studied. The main objective of the present study was to systematically evaluate the effects of three MLs, i.e. eprinomectin (EPR), moxidectin (MOX) or ivermectin (IVM), on PRMs fed on chicks following oral administration.

Methods

Chicks in treatment groups were orally administrated with EPR, MOX or IVM at a dose of 5.0 mg/kg bodyweight. Chicks in the control group received the carrier solvent without drug. Chicks in each cage were then infested with 200 starved adult D. gallinae. After infestation and feeding for 12 h, engorged mites were collected to evaluate the acaricidal efficacy of the MLs, and its impacts on the reproduction and blood-meal digestion of D. gallinae.

Results

MOX, IVM and EPR demonstrated higher acaricidal efficacies post-treatment compared with the control, i.e. 45.60% for MOX, 71.32% for IVM and 100% for EPR on Day 10. MLs did not have significant effects on the blood-meal ingestion of PRMs, but significantly slowed down blood digestion (P < 0.0001). The oviposition rate, egg hatching rate and fecundity of PRMs in treatment groups were remarkably reduced. Among the three MLs, EPR exhibited the highest performance against PRMs, with an oviposition rate of 1.04%, fecundity of 0.33 eggs per mite and a zero egg hatching rate in EPR treated groups.

Conclusions

EPR, MOX or IVM administrated orally to chicks increased the mortality of D. gallinae, significantly slowed down their blood-meal digestion and significantly reduced their reproductive capability which included the oviposition rate, fecundity and egg hatching rate. The present study highlights the potential of MLs in the control of PRMs.

Population fluctuation of predatory and sanitary importance mites (Acari) in commercial laying hens: Ecological interactions

This study aimed to evaluate the mite fauna and their ecological interactions in commercial laying hen farms in the state of Rio Grande do Sul, Brazil. It was conducted from August 2013 through August 2014 with two sampling strategies (feathers and traps) in three different production systems: automated (A_1,2,3), semi-automated (S_1,2) and free-range (FR). A total of 38,383 mites were collected belonging to 23 families and 33 species, most of which were collected in feathers (74%) followed by traps (26%). There was higher abundance at S₁ (10,774-28.1%) and S₂ (11,023-28.7%) followed by FR (6972-18.2%), A₁ (1896-4.9%), A₂ (4775-12.4%), and A₃ (2943-7.7%). Higher richness was observed at S₁ (23 species), S₂ (18 species), and FR (19 species). Megninia ginglymura (Mégnin) (Analgidae) was the species with the highest health importance, eudominant on feathers, and its populations seems to be related with increased temperature. Tuccioglyphus setosus Horn et al. (Pyroglyphidae) seems to be influenced by relative air humidity and temperature. Predators with the highest populations were Cheyletus malaccensis (Oudemans) (Cheyletidae), Typhlodromus transvaalensis (Nesbitt) (Phytoseiidae), Blattisocius keegani (Fox), and Blattisocius dentriticus (Berlese) (Blattisocidae).

Survey on the prevalence of Dermanyssus gallinae in commercial laying farms in Portugal

Dermanyssus gallinae, also known as the poultry red mite (PRM), is a blood-feeding ectoparasite of poultry and sylvatic birds. This mite is endemic in many parts of the globe and poses a threat to the egg industry, while compromising the health and welfare of hens, both directly and as a vector of diseases. In addition, people attacked by D. gallinae may develop gamasoidosis. Despite the high prevalence in several European countries, epidemiological information on D. gallinae in Portugal is scarce. This study aimed to assess the prevalence and infestation levels in laying farms in Portugal and evaluate the perception and attitudes of producers regarding D. gallinae. A survey was performed between August 2016 - November 2017, which included 24 farms in the NUTS2 regions Centro and Norte. Mites were sampled with corrugated cardboard traps and the perception and attitudes of farmers regarding the PRM were evaluated with the European COREMI questionnaire prepared by WG 1 of the COST action FA1404. D. gallinae was detected in 95.8% of farms (95% CI: 79.8-99.3%). The average number of trapped mites among farms was 5200 ± 16,522, with a median of 359 mites (interquartile range = 46-3135). Results from the questionnaire show that insufficient monitoring, under-detection and late and suboptimal treatment may contribute to the maintenance of significant infestation levels. The present data highlight the need for adequate monitoring of D. gallinae, timely action and effective treatment in order to improve poultry productivity and ensure human and animal health and welfare. RESEARCH HIGHLIGHTS A survey on the prevalence of D. gallinae in Portuguese layer farms is presented The perceived importance of D. gallinae was assessed with a questionnaire D. gallinae was detected in 95.8% of farms The results emphasize the need for adequate monitoring and treatment optimization.

Evaluation of the Common Bed Bug, Cimex lectularius (Insecta: Hemiptera: Cimicidae) Susceptibility to λ-Cyhalothrin, Malathion, and Diazinon in Northeastern Iran

The common bed bug, Cimex lectularius (Linnaeus 1758), is a nocturnal blood-sucking ectoparasite of humans that is highly prevalent in the northeast of Iran. In recent years, the efficacy of those insecticides that have been frequently used to control bed bugs in Iran has not been studied. Due to frequent complaints about bed bug treatment failures in Mashhad city (northeastern Iran), this study assessed the susceptibility of C. lectularius collected from a student residence hall to Diazinon, Malathion, and λ-cyhalothrin. The desired concentrations of each insecticide were prepared in acetone, and bioassays were performed using insecticide-impregnated filter paper method. The concentration-response data were subjected to POLO-PC software and data were analyzed by the log-probit procedure. The LC50 values of Diazinon and λ-cyhalothrin for examined bed bugs were 1,337.40 and 2,022.36 ppm, respectively. Malathion at the highest concentration (10,000 ppm) did not exhibit any toxicity to examined C. lectularius. Comparing these results to the same previous studies showed that susceptibility of examined bed bugs to these insecticides has been highly decreased. This study revealed an occurrence of insecticide resistance in bed bug populations in northeastern Iran. It also suggests that Malathion, Diazinon, and λ-cyhalothrin are ineffective against bed bugs in this region.

Linking morphological and molecular taxonomy for the identification of poultry house, soil, and nest dwelling mites in the Western Palearctic

Because of its ability to expedite specimen identification and species delineation, the barcode index number (BIN) system presents a powerful tool to characterize hyperdiverse invertebrate groups such as the Acari (mites). However, the congruence between BINs and morphologically recognized species has seen limited testing in this taxon. We therefore apply this method towards the development of a barcode reference library for soil, poultry litter, and nest dwelling mites in the Western Palearctic. Through analysis of over 600 specimens, we provide DNA barcode coverage for 35 described species and 70 molecular taxonomic units (BINs). Nearly 80% of the species were accurately identified through this method, but just 60% perfectly matched (1:1) with BINs. High intraspecific divergences were found in 34% of the species examined and likely reflect cryptic diversity, highlighting the need for revision in these taxa. These findings provide a valuable resource for integrative pest management, but also highlight the importance of integrating morphological and molecular methods for fine-scale taxonomic resolution in poorly-known invertebrate lineages.

Efficacy of a novel neem oil formulation (RP03™) to control the poultry red mite Dermanyssus gallinae

Dermanyssus gallinae (Mesostigmata: Dermanyssidae) is the most harmful ectoparasite of laying hens, represents an occupational hazard for poultry workers, and a growing threat to medical science per se. There is increasing demand for alternative products, including plant-derived acaricides, with which to control the mite. The present study investigated the efficacy of neem oil against D. gallinae on a heavily infested commercial laying hen farm. A novel formulation of 20% neem oil, diluted from a 2400-p.p.m. azadirachtin-concentrated stock (RP03™), was administered by nebulization three times in 1 week. Using corrugated cardboard traps, mite density was monitored before, during and after treatment and results were statistically analysed. Mite populations in the treated block showed 94.65%, 99.64% and 99.80% reductions after the first, second and third product administrations, respectively. The rate of reduction of the mite population was significantly higher in the treated block (P < 0.001) compared with the control and buffer blocks. The results suggest the strong bioactivity of neem, and specifically of the patented neem-based formulation RP03™, against D. gallinae. The treatment was most effective in the 10 days following the first application and its effects persisted for over 2 months. Further studies will aim to overcome observed side effects of treatment represented by an oily layer on equipment and eggs.

Spotlight on avian pathology: red mite, a serious emergent problem in layer hens

Dermanyssus gallinae, the poultry red mite, is currently the most important ectoparasite of the egg laying industry worldwide with an expanding global prevalence. As a blood-feeder, it causes anaemia and severe welfare issues to the hens and it is a major cause of economic losses. It is also a vector for Salmonella species, avian influenza and potentially for other vector-borne pathogens. Paradoxically, there is a notable lack of funding for research into poultry red mite and an urgent need for effective and safe control strategies, sustainable therapies, prophylactics and integrated pest management.

Experimental validation of the AVIVET trap, a tool to quantitatively monitor the dynamics of Dermanyssus gallinae populations in laying hens

Dermanyssus gallinae (D.gallinae) infestation causes economic losses due to impaired health and production of hens and costs of parasite control across the world. Moreover, infestations are associated with reduced welfare of hens and may cause itching in humans. To effectively implement control methods it is crucially important to have high quality information about the D.gallinae populations in poultry houses in space and time. At present no validated tool is available to quantitatively monitor the dynamics of all four stages of D.gallinae (i.e., eggs, larvae, nymphs, and adults) in poultry houses.This article describes the experimental validation of the AVIVET trap, a device to quantitatively monitor dynamics of D.gallinae infestations. We used the device to study D.gallinae in fully equipped cages with two white specific pathogen free Leghorn laying hens experimentally exposed to three different infestation levels of D.gallinae (low to high).The AVIVET trap was successfully able to detect D.gallinae at high (5,000 D.gallinae), medium (2,500 D.gallinae), and low (50 D.gallinae) level of D.gallinae infestation. The linear equation Y = 10∧10∧(0.47 + 1.21X) with Y = log10 (Total number of D.gallinae nymphs and adults) in the cage and X = log10 (Total number of D.gallinae nymphs and adults) in the AVIVET trap explained 93.8% of the variation.The weight of D.gallinae in the AVIVET trap also appears to be a reliable parameter for quantifying D.gallinae infestation in a poultry house. The weight of D.gallinae in the AVIVET trap correlates 99.6% (P < 0.000) to the counted number of all stages of D.gallinae in the trap (i.e., eggs, larvae, nymphs, and adults) indicating that the trap is highly specific.From this experiment it can be concluded that the AVIVET trap is promising as quantitative tool for monitoring D.gallinae dynamics in a poultry house.