Acaricidal drug resistance in poultry red mite (Dermanyssus gallinae) and approaches to its management

Residue, distribution and depletion of fluralaner in egg following a single intravenous and transdermal administration in healthy shaver hens: fluralaner residue in egg

The demand for the use of fluralaner in an extra label manner is increasing due to lack of efficacious treatment to combat mites and bed bugs in the poultry industry in the United States. Fluralaner residue data in eggs is lacking and residues might cause risks to human health. The present study aimed to determine the depletion profiles of fluralaner in eggs and estimate the drug withdrawal interval in whole eggs by adopting the US Food and Drug administration tolerance limit method with single intravenous (0.5 mg/kg) or transdermal administration (average 58.7 mg/kg) in healthy shaver hens. Hens were treated intravenously or trans-dermally with fluralaner. The eggs were collected daily for 28 d for intravenous treated and for 40 d from the transdermal route group. Fluralaner concentrations in yolk and albumen were determined by mass spectrometry. The greater percentage of fluralaner was observed in yolk when compared to the albumen for both administration routes. Noncompartmental analysis was used to calculate the pharmacokinetic parameters in yolk, albumen and whole egg. The longest apparent half-life confirmed in yolk was 3.7 d for intravenous and 14.3 d for the transdermal route. The withdrawal intervals in whole egg for fluralaner following the intravenous and transdermal administration were 7 d and 81 d, respectively, with maximum residue limits (1.3 µg/g) at 13 d and 171 d, respectively, based on the limit of quantification (0.4 µg/g) from the analytical assay reported by EMA and APVMA.

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.

Pharmacokinetics of intravenously and trans-dermally administered fluralaner in healthy laying shaver hens: fluralaner in chickens

Ectoparasite infestations negatively affect both backyard and commercial chicken flocks in the United States. Fluralaner is an isoxazoline shown to be efficacious in treating mite and bed bug infestations in poultry. Fluralaner is approved to treat fleas and ticks in dogs and cats in the United States and to treat mite infestations of chickens in Europe and Australia; however, the use of fluralaner in poultry is not yet approved in the United States. This study aimed to investigate the plasma fluralaner pharmacokinetic profile of intravenous and transdermal routes and apparent bioavailability of fluralaner administered trans-dermally in healthy shaver hens. A total of 12 individually housed healthy shaver hens received a single dose of either intravenous technical grade fluralaner at 0.5 mg/kg, or transdermal fluralaner (Bravecto (fluralaner transdermal solution) for dogs, 280 mg/mL, Merck Animal Health) at mean 58.7 mg/kg. Plasma from each hen was collected from the jugular, ulnar, or medial metatarsal vein at multiple intervals. Fluralaner concentrations in plasma were determined using Ultra Performance Liquid Chromatography with Mass Spectrometry (UPLC/MS). Noncompartmental analysis revealed that the geometric mean elimination half-life for intravenous and transdermal routes were 80.5 and 179.6 h, respectively. The geometric mean apparent bioavailability of transdermal routes was estimated as 3.4%. Prolonged fluralaner concentration in plasma above minimum inhibitory concentration of bed bugs following the single dose was observed in healthy shaver hens for both routes. It is important to understand the pharmacokinetic profile could be useful in determining the appropriate treatment strategy.

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.

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.

Challenges in the Biological Control of Pests in Poultry Production: a Critical Review of Advances in Brazil

Poultry farming is an important activity in animal protein production worldwide, either by laying hen farming or broilers. Over the last decades, the change in production systems with confinement of large numbers of hens has increased productivity and reduced costs; however, it has also increased sanitary issues. In this setting, arthropods that are adapted to poultry houses have gained great importance. They cause direct damage to hens, either by blood spoliation caused by ectoparasites or lesions in the digestive tract (e.g., lesser mealworm) or by indirect damages, by transmitting pathogens or by affecting egg quality, when they attain pest status. Synthetic chemical products comprise the most frequently used control strategy against these pests, with relative efficacy and many side effects. In Europe, some countries also adopt alternative prevention or control measures. In Brazil, however, although there are some groups of researchers that work on developing alternative control, its use is virtually zero. The present review shows a critical overview of this context in Brazil, based on the alternatives that have already been studied and made available, but have not been implemented, yet, and the potential stumbling blocks created by the very poultry market against these advances.

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.

Short-time cold atmospheric pressure plasma exposure can kill all life stages of the poultry red mite, Dermanyssus gallinae, under laboratory conditions

In the present study, the acaricidal effects of cold atmospheric pressure plasma treatment on poultry red mites of different developmental stages have been investigated under laboratory conditions using a dielectric barrier discharge system. A total of 1890 poultry red mites and 90 mite eggs, respectively, were exposed to the plasma under various parameter settings with a single plasma pulse generated using the gas mixture of the ambient air at atmospheric pressure. The results showed that all developmental stages of the poultry red mite could be killed by cold atmospheric pressure plasma treatment. Plasma exposure to mite eggs resulted in a complete 100% hatch inhibition regardless of the parameter settings. Post-exposure mortality rates of larvae, nymphs and adults showed significant differences after utilization of plasma at 10 W for 1.0 s. In addition, the mortality rate increased with progressing time after plasma exposure. An average mortality rate of 99.7% was observed after 12 h in all mites exposed to plasma, regardless of the selected plasma parameter, developmental stage, and nutritional status of the mites. Cold atmospheric pressure plasma has an acaricidal effect on all developmental stages of Dermanyssus gallinae, suggesting that it could be developed to an effective method for the control of poultry red mites in laying hen husbandry.

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.

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.

Two ferritins from Dermanyssus gallinae: characterization and in vivo assessment as protective antigens

BACKGROUND

The poultry red mite, Dermanyssus gallinae is recognized worldwide as the most important bloodsucking ectoparasite in layer and breeder flocks. In bloodsucking ectoparasites, ferritins (FERs), the iron-storage proteins, play a pivotal role in dealing with the challenge of large amounts of released iron during the digestion of blood meal. However, no information is available concerning FERs of D. gallinae. The aim of the present study was to investigate the characteristics, functions and the vaccine efficacy of FERs in D. gallinae.

RESULTS

Two heavy-chain FERs of D. gallinae were identified and characterized. Phylogenetic analysis indicated that Dg-FER1 may be a secretory FER and Dg-FER2 an intracellular one. RNAi results demonstrated that Dg-fers play key roles in mite survival, successful reproduction and blood digestion. Immunization with rDg-FER1 or rDg-FER2 successfully induced chickens to produce high levels of antigen-specific IgY, resulting in a significant increase in mite mortality (by 58.67% on Day 5) and decreases in oviposition (by 42.15%) and fecundity (by 68.97%) in the rDg-FER1 group, and a 13.73% increase in mite mortality and a 20.89% decrease in fecundity in the rDg-FER1 group. The overall immunization efficacy of rDg-FER1 was 93.51%.

CONCLUSION

Two Dg-FERs are crucial to the survival, reproduction and blood digestion of D. gallinae. This study has provided preliminary evidence demonstrating the potential of rDg-FER1 as a vaccine antigen for D. gallinae. © 2021 Society of Chemical Industry.

The Effects of Feed Intake and Water Hardness on Fluralaner Pharmacokinetics in Layer Chickens

Background

Fluralaner is a novel drug belonging to the isoxazoline class that acts on external parasites of domestic animals. It is used systemically via drinking water, especially against red poultry mite in layer chickens. Fluralaner is frequently used in layers infected with D. gallinae. However, no study to date has investigated the effects of feed intake and water hardness.

Objectives

This study aimed to investigate the effects of variable water hardness and feed intake on the pharmacokinetic profile of fluralaner.

Methods

Layer chickens were divided into four groups (n = 8): fed + purified water (Group 1), feed restricted + purified water (Group 2), feed restricted + hard water (Group 3), and feed restricted + soft water (Group 4). After administering a single dose of the drug with drinking water, the blood samples were collected for 21 days. Fluralaner concentrations in plasma samples were determined by liquid chromatography/tandem mass spectrometry. The maximum plasma concentration (C_max), time to reach maximum plasma concentration (t_max), area under the concentration–time curve values (AUC_0-21d), half-life (t_1/2), and other pharmacokinetic parameters were calculated.

Results

Although the highest maximum plasma concentration (C_max) was determined in Group 1 (fed + purified water), no statistically significant difference was found in the C_max, t_max, t_1/2, MRT_{0-inf_obs}, Vz/F_obs, and Cl/F_{_obs} parameters between the experimental groups.

Conclusions

It was concluded that the feed intake or water hardness did not change the pharmacokinetic profile of fluralaner in layer chickens. Therefore, fluralaner could be used before or after feeding with the varying water hardness in poultry industry.

Importance and Impact of the Poultry Red Mite (Dermanyssus gallinae) in Layer Farms - Analysis of Farmers’ Perception

Poultry red mite (PRM), Dermanyssus gallinae, causes egg drop production, anemia and can be a vector in transmitting diseases. The PRM control mainly focuses on usage of the conventional chemical biocides. The objective of this study was to analyze the farmers’ perception regarding the impact, management and control of PRM in Macedonian layer farms. The data were collected with direct on-site visits using a unified questionnaire. In total, 29 poultry farms (28% of farms in the country), all with conventional cages, were part of this study. The data were analyzed by descriptive statistics, inferential statistics and Naïve Bayes Classifier technique. In 30% of the poultry farms the farmers had observed that the flock was infested with PRM. In total, 32 different treatments against PRM were reported from the farmers, and three of them were non-biocide treatments. The most used biocides (17% of the farms) were crude oil, Formalin, Neopitroid® and disinfectants. The highest agreement regarding biocides application among the farms (38%) was before the production starts. Most of the farmers applied biocides routinely, before the infestation is evident (75%). The median costs for PRM treatment were 175€ per flock, higher in the infested farms 493±677€ compared to non - infested 100±71€, p<0.05. None of the Macedonian farmers included in the study was using monitoring method for PRM infestation, contributing to poor data records. This study highlights the need of developing unified strategy for PRM control included in the Integrated Pest Management in poultry layer farms.

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.

RNAi gene knockdown in the poultry red mite, Dermanyssus gallinae (De Geer 1778), a tool for functional genomics

Background

The avian haematophagous ectoparasite Dermanyssus gallinae, commonly known as the poultry red mite, causes significant economic losses to the egg-laying industry worldwide and also represents a significant welfare threat. Current acaricide-based controls are unsustainable due to the mite’s ability to rapidly develop resistance, thus developing a novel sustainable means of control for D. gallinae is a priority. RNA interference (RNAi)-mediated gene silencing is a valuable tool for studying gene function in non-model organisms, but is also emerging as a novel tool for parasite control.

Methods

Here we use an in silico approach to identify core RNAi pathway genes in the recently sequenced D. gallinae genome. In addition we utilise an in vitro feeding device to deliver double-stranded (ds) RNA to D. gallinae targeting the D. gallinae vATPase subunit A (Dg vATPase A) gene and monitor gene knockdown using quantitative PCR (qPCR).

Results

Core components of the small interfering RNA (siRNA) and microRNA (miRNA) pathways were identified in D. gallinae, which indicates that these gene silencing pathways are likely functional. Strikingly, the P-element-induced wimpy testis (PIWI)-interacting RNA (piRNA) pathway was absent in D. gallinae. In addition, feeding Dg vATPase A dsRNA to adult female D. gallinae resulted in silencing of the targeted gene compared to control mites fed non-specific lacZ dsRNA. In D. gallinae, dsRNA-mediated gene knockdown was rapid, being detectable 24 h after oral delivery of the dsRNA, and persisted for at least 120 h.

Conclusions

This study shows the presence of core RNAi machinery components in the D. gallinae genome. In addition, we have developed a robust RNAi methodology for targeting genes in D. gallinae that will be of value for studying genes of unknown function and validating potential control targets in D. gallinae.

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.

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.

An efficient high-welfare feeding device for assessing northern fowl mite interventions in vivo: an improved method for the identification of protective antigens/systemic acaricides/repellent effect

The northern fowl mite (NFM), Ornithonyssus sylviarum, is an obligate hematophagous ectoparasite of domestic and wild birds, and it is an economic pest of laying hen in North America, China, India, Australia, Myanmar, and Brazil. Such an economically important pest remains neglected in many parts of the world, including Asian countries. Therefore, concerted action is required in both basic and applied research directed at the biology and control of this destructive pest. In the present study, we have developed a novel, high-welfare in vivo feeding capsule that would permit pre-screening of new interventions, repellency and deterrence effects of plant-derived products and other semiochemical compounds before proceeding to large-scale field experiments/bioassays, while the minimum number of animals is required to obtain results. Mites were fed on the birds through either a mesh or without a mesh. The average feeding rates of mites was significantly higher when fed directly on chickens, whereas 106 μm nylon mesh was the top-performing mesh when compared with 125 μm aperture nylon mesh. For optimal feeding, the feeding capsules contain NFM and are attached to the skin of the chicken's thigh for 6 h. This is a simple, reproducible, and easy approach and can be adapted to facilitate many aspects of bioassays.

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.

Laboratory and field evaluation of an autoinoculation device as a tool to manage poultry red mite, Dermanyssus gallinae, infestations with Beauveria bassiana

The poultry red mite, Dermanyssus gallinae, is a cosmopolitan ectoparasite in hens and has been considered an important threat to the egg production industry. This study evaluated an alternative to manage poultry red mite populations as a complement to conventional chemical treatments and other control strategies in poultry houses. A simple autoinoculation device prepared with corrugated cardboard (CB) or loofah sponge (LS) as inert supports to anchor Beauveria bassiana conidia was used to aggregate and infect mites from infested poultry houses. In the laboratory, mites gathered inside the traps and the average mortalities by the fungus were higher than 70% in CB and LS traps after 5 and 4 days of exposure, respectively. Conidial viability was around 80% in CB and LS traps after 14 and 60 days under unrefrigerated conditions (26 °C), respectively. Both trap types tied to hen cages efficiently captured fed mites after blood meal, and fungal infection was observed in 65-90% of the mites in field tests. Between 5 and 25% of the mites recaptured in monitoring cardboard traps installed immediately after CB and LS removal were infected by B. bassiana. According to our results, the use of B. bassiana in an autoinoculation strategy is a potential alternative method for D. gallinae control.

Active components of essential oils as acaricides against Dermanyssus gallinae

1. The aim was to evaluate the acaricidal effects of pure active components of essential oils against poultry red mite (Dermanyssus gallinae) as an alternative to chemical acaricides (organophosphates and pyrethroids).2. The toxicities of five pure active components of essential oils (eugenol from clove bud, eucalyptol from rosemary, limonene from citrus fruits, linalool from lavender and cinnamaldehyde from cinnamon) were tested on D. gallinae females in an impregnated paper assay.3. The active substances were dissolved in water and Tween 20 and applied at concentrations ranging from 0.002 to 0.06 µl/cm². Toxicity was expressed as a lethal dose (LD₅₀ or LD₉₀).4. The highest mortality was observed with eugenol. The LD₉₀ was estimated to be 5.1 µg/cm² for this substance, followed by cinnamaldehyde, the LD₉₀ of which was estimated to be 11.0 µg/cm². Limonene and eucalyptol were generally less effective in controlling D. gallinae.

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.

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.

Evaluation of vaccine delivery systems for inducing long-lived antibody responses to Dermanyssus gallinae antigen in laying hens

Dermanyssus gallinae, the poultry red mite, is a global threat to the commercial egg-laying industry. Control of D. gallinae is difficult, with only a limited number of effective pesticides and non-chemical treatments available. Here, we characterize the candidate vaccine antigen D. gallinae cathepsin D-1 (Dg-CatD-1) and demonstrate that purified refolded recombinant Dg-Cat-D1 (rDg-CatD-1) is an active aspartyl proteinase which digests haemoglobin with a pH optimum of pH 4. Soluble protein extracts from D. gallinae also have haemoglobinase activity, with a pH optimum comparable to the recombinant protein, and both proteinase activities were inhibited by the aspartyl proteinase inhibitor Pepstatin A. Enzyme activity and the ubiquitous localization of Dg-CatD-1 protein in sections of adult female mites is consistent with Dg-CatD-1 being a lysosomal proteinase. Using Dg-CatD-1 as a model vaccine antigen, we compared vaccine delivery methods in laying hens via vaccination with: (i) purified rDg-CatD-1 with Montanide™ ISA 71 VG adjuvant; (ii) recombinant DNA vaccines for expression of rDg-CatD-1 and (iii) transgenic coccidial parasite Eimeria tenella expressing rDg-CatD-1. In two independent trials, only birds vaccinated with rDg-CatD-1 with Montanide™ ISA 71 VG produced a strong and long-lasting serum anti-rDg-Cat-D1 IgY response, which was significantly higher than that in control birds vaccinated with adjuvant only. Furthermore, we showed that egg-laying rates of D. gallinae mites fed on birds vaccinated with rDg-CatD-1 in Montanide™ ISA 71 VG was reduced significantly compared with mites fed on unvaccinated birds. RESEARCH HIGHLIGHTS Dermanyssus gallinae cathepsin D-1 (Dg-CatD-1) digests haemoglobin Vaccination of hens with rDg-CatD-1 in Montanide™ ISA 71 VG results in long-lasting IgY levels Serum anti-rDg-CatD-1 antibodies reduce egg laying in D. gallinae after a single blood meal.

Toxicity and effects of essential oils and their components on Dermanyssus gallinae (Acari: Dermanyssidae)

The acaricidal activity of 30 essential oils against the poultry red mite, Dermanyssus gallinae, female adults and behavioral responses of the mites to these essential oils were investigated. Cinnamon bark oil and clove bud oil showed 100% acaricidal activity after 24 h in the 1.3 μg/m² treatment. In addition, four components in cinnamon bark oil and three components in clove bud oil were identified using gas chromatography-mass spectrometry. Cinnamon bark oil showed the highest LD₅₀ value among all of the components, and eugenol showed 0.97-fold higher relative toxicity (RT) than the other components of clove bud oil. The fumigant effects of both essential oils and their seven components were observed using a vapor phase toxicity bioassay. All the substances showed repellent activity except for cinnamyl acetate, which did not show any repellent response even in the > 10 μg treatment. In the experiment using the T-tube olfactometer with the 10 μg treatment of each substance, D. gallinae female adults responded to all the substances except cinnamyl acetate. However, eugenol and eugenol acetate showed an attractant effect after 240 and 120 min of treatment, respectively. These results suggest that the two studied essential oils and their components may be used as control agents against D. gallinae.

Benzoylphenyl ureas as veterinary antiparasitics. An overview and outlook with emphasis on efficacy, usage and resistance

Six benzoylphenyl ureas are currently used in formulations approved as veterinary medicines: diflubenzuron for fly control mainly on cattle, lice and blowfly strike control on sheep, and lice control on farmed salmonids; lufenuron for flea control on dogs and cats and for lice control on farmed salmonids; triflumuron for lice and blowfly strike control on sheep; fluazuron for tick control on cattle; teflubenzuron for lice control on farmed salmon; and novaluron for fly and tick control on cattle and for flea control on dogs. Resistance to diflubenzuron and triflumuron has already been reported for sheep body lice and blowflies, and to fluazuron in cattle ticks. These and other minor veterinary usages, as well as the current status of resistance, are reviewed and perspectives for future opportunities are discussed based on unexplored potentials and threats posed by future resistance development.

In vitro activity of fluralaner and commonly used acaricides against Dermanyssus gallinae isolates from Europe and Brazil

Background

The poultry red mite Dermanyssus gallinae negatively impacts bird welfare and health, and interferes with egg production and quality, while emerging acaricide resistance limits control options. Fluralaner, a novel miticide for administration in drinking water, is approved for control of D. gallinae infestations. Mite sensitivity testing is relevant to gauge field isolate susceptibility to available treatments.

Methods

Thirteen D. gallinae isolates collected during 2014 through 2016 from farms in Germany, France, Spain and Brazil, and a 2001 laboratory-maintained isolate were used for acaricide contact sensitivity testing. Tested compounds were cypermethrin, deltamethrin, phoxim, propoxur, and the recently available acaricides, spinosad and fluralaner. In each study, at least one isolate was exposed to increasing concentrations of at least one acaricide. In one study, additional testing determined the sensitivity of the 2001 isolate to fluralaner using a mite-feeding test, and of fluralaner, phoxim and spinosad using an immersion test. At least two replicates were used for each dilution. Vehicle and untreated controls were also included.

Results

Based on 90% mortality (LC₉₀) values, the laboratory isolate was susceptible to fluralaner (15.6–62.5 parts per million, ppm), phoxim (< 500 ppm), propoxur (< 125 ppm), and deltamethrin (500–1000 ppm). All field isolates remained sensitive to fluralaner concentrations ≤ 125 ppm. Spinosad LC₉₀ values for laboratory and field isolates ranged between 2000–4000 ppm. For phoxim, relative to the laboratory isolate, there was reduced sensitivity of two German isolates (LC₉₀ up to 4000 ppm) and two French isolates (> 4000 ppm). An isolate from Spain demonstrated reduced sensitivity to phoxim, propoxur and deltamethrin; an isolate from Brazil showed reduced sensitivity to propoxur and cypermethrin. Mite LC₉₀ when exposed to fluralaner by blood feeding was < 0.1 ppm.

Conclusions

Contact sensitivity testing indicated apparent resistance to at least one of phoxim, deltamethrin, cypermethrin and propoxur in 13 field isolates from Europe and Brazil. All isolates were highly susceptible to fluralaner. Fluralaner was approximately 1000 times more active by feeding than by contact. Fluralaner’s distinct mode of action and efficacy against isolates largely refractory to those acaricides, makes it a promising option for the control of D. gallinae infestations of poultry.

The acaricidal speed of kill of orally administered fluralaner against poultry red mites (Dermanyssus gallinae) on laying hens and its impact on mite reproduction

BACKGROUND

Dermanyssus gallinae, the poultry red mite, is a growing threat to chickens in poultry farms. This nocturnal hematophagous ectoparasite has a rapid rate of proliferation with a negative impact on the birds' health, welfare and productivity resulting in severe economic consequences for poultry farmers. A study was performed with fluralaner, a novel systemic ectoparasiticide, to evaluate its effect on mite vitality and reproduction after oral administration to laying hens.

METHODS

Sixteen healthy hens were randomly allocated to two study groups (n = 8). One group was orally treated with fluralaner by gavage at a dose of 0.5 mg/kg bodyweight twice 7 days apart. The negative control group received no treatment. Hens in each group were repeatedly infested with approximately 200 unfed adult D. gallinae at 1, 5, 8, 12, 15, 19, 22 and 26 days after the initial administration. After infestation and feeding for 2.5 h, 25 engorged mites per hen were collected and incubated in tubes. Mites were assessed for vitality (dead/live) at 4, 8, 12, and 24 h after each infestation. Tubes containing eggs and/or living mites were incubated another 8 days for assessment of mite reproductive capacity.

RESULTS

Fluralaner demonstrated a fast speed of kill in mites within 4 h post-infestation for 12 days after treatment initiation. An efficacy (mite mortality) of 98.7-100% was achieved. At 15 days after treatment initiation, 100% efficacy was achieved within 24 h post-infestation, and no mite oviposition occurred during this period. Nineteen days after treatment initiation, the mites' ability to generate nymphs was reduced by 90.8%, which decreased to < 24.1% at later infestations.

CONCLUSIONS

Fluralaner administered orally to hens twice, 7 days apart, provides efficacy against experimental poultry red mite infestation for at least 2 weeks. The demonstrated rapid speed of kill results in substantial depletion of the mites' oviposition and suggests that fluralaner can be an effective tool in the control of D. gallinae, one of the most urgent problems in poultry farms.

Field efficacy and safety of fluralaner solution for administration in drinking water for the treatment of poultry red mite (Dermanyssus gallinae) infestations in commercial flocks in Europe

Background

Welfare concerns, production losses caused by Dermanyssus gallinae, the poultry red mite (PRM), and widespread mite resistance to environmentally applied acaricides continue to drive an urgent need for new and effective control measures. Fluralaner is a novel systemic acaricide developed to address that need. A series of field studies was initiated to investigate the safety and efficacy of a fluralaner solution (10 mg/ml) administered in drinking water at a dose rate of 0.5 mg/kg on two occasions with a 7-day interval, for treatment of natural PRM infestations in chickens.

Methods

Blinded, negative-controlled studies were completed in Europe across eight layer, two breeder, and two replacement chicken farms. At each farm, two similar flocks were housed in similar PRM-infested units (either rooms within a building, or separate buildings) varying from 550 to 100,000 birds per unit. One unit at each farm was allocated to fluralaner treatment, administered in drinking water on Days 0 and 7. One unit remained untreated. Mite traps were placed throughout each unit on Days -1, 0 or 1, 3, 6, 9, and 13 or 14, then at weekly or two-weekly intervals, retrieved after 24 h and processed for mite counts. Efficacy at each farm was assessed by mean PRM count reductions from traps in treated units compared with those from control units. Production parameters and safety were also monitored.

Results

Efficacy was 95.3 to 99.8% on Day 3 and 97.8 to 100% on Day 9, thereafter remaining above 90% for 56 to 238 days after treatment initiation. Post-treatment improvement in egg-laying rate was greater by 0.9 to 12.6% in the treated group at 9 of the 10 layer or breeder farms. There were no treatment-related adverse events.

Conclusion

Fluralaner administered at 0.5 mg/kg via drinking water twice, 7 days apart, was well tolerated and highly efficacious against the PRM in naturally infested chickens representing a range of production types and management systems. The results indicate that this novel treatment has potential to be the cornerstone of an integrated approach to reducing or eliminating the welfare and productivity costs of this increasingly threatening pest.

Comparative in vitro evaluation of contact activity of fluralaner, spinosad, phoxim, propoxur, permethrin and deltamethrin against the northern fowl mite, Ornithonyssus sylviarum

Background

Northern fowl mites (Ornithonyssus sylviarum) are obligate hematophagous ectoparasites of both feral birds and poultry, particularly chicken layers and breeders. They complete their entire life-cycle on infested birds while feeding on blood. Infestations of O. sylviarum are difficult to control and resistance to some chemical classes of acaricides is a growing concern. The contact susceptibility of O. sylviarum to a new active ingredient, fluralaner, was evaluated, as well as other compounds representative of the main chemical classes commonly used to control poultry mite infestations in Europe and the USA.

Methods

Six acaricides (fluralaner, spinosad, phoxim, propoxur, permethrin, deltamethrin) were dissolved and serially diluted in butanol:olive oil (1:1) to obtain test solutions used for impregnation of filter paper packets. A carrier-only control was included. Thirty adult northern fowl mites, freshly collected from untreated host chickens, were inserted into each packet for continuous compound exposure. Mite mortality was assessed after incubation of the test packets for 48 h at 75% relative humidity and a temperature of 22 °C.

Results

Adult mite LC₅₀ /LC₉₉ values were 2.95/8.09 ppm for fluralaner, 1587/3123 ppm for spinosad, 420/750 ppm for phoxim and 86/181 ppm for propoxur. Permethrin and deltamethrin LC values could not be calculated due to lack of mortality observed even at 1000 ppm.

Conclusions

Northern fowl mites were highly sensitive to fluralaner after contact exposure. They were moderately sensitive to phoxim and propoxur, and less sensitive to spinosad. Furthermore, the tested mite population appeared to be resistant to the pyrethroids, permethrin and deltamethrin, despite not being exposed to acaricides for at least 10 years.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2289-z) contains supplementary material, which is available to authorized users.

Poultry red mite (Dermanyssus gallinae) infestation: a broad impact parasitological disease that still remains a significant challenge for the egg-laying industry in Europe

The poultry red mite, Dermanyssus gallinae, has been described for decades as a threat to the egg production industry, posing serious animal health and welfare concerns, adversely affecting productivity, and impacting public health. Research activities dedicated to controlling this parasite have increased significantly. Their veterinary and human medical impact, more particularly their role as a disease vector, is better understood. Nevertheless, red mite infestation remains a serious concern, particularly in Europe, where the prevalence of red mites is expected to increase, as a result of recent hen husbandry legislation changes, increased acaricide resistance, climate warming, and the lack of a sustainable approach to control infestations. The main objective of the current work was to review the factors contributing to this growing threat and to discuss their recent development in Europe. We conclude that effective and sustainable treatment approach to control poultry red mite infestation is urgently required, included integrated pest management.

Field evaluation of poultry red mite (Dermanyssus gallinae) native and recombinant prototype vaccines

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Field trial testing of a native and recombinant poultry red mite vaccines.

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Vaccination with a soluble mite extract (SME) resulted in a 78% reduction in mite numbers.

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Poor antibody persistence may relate to lack of effect of a recombinant cocktail vaccine.

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A semi-protective naturally acquired immunity may develop.

Vaccination is a desirable emerging strategy to combat poultry red mite (PRM), Dermanyssus gallinae. We performed trials, in laying hens in a commercial-style cage facility, to test the vaccine efficacy of a native preparation of soluble mite extract (SME) and of a recombinant antigen cocktail vaccine containing bacterially-expressed versions of the immunogenic SME proteins Deg-SRP-1, Deg-VIT-1 and Deg-PUF-1. Hens (n = 384 per group) were injected with either vaccine or adjuvant only (control group) at 12 and 17 weeks of age and then challenged with PRM 10 days later. PRM counts were monitored and, at the termination of the challenge period (17 weeks post challenge), average PRM counts in cages containing birds vaccinated with SME were reduced by 78% (p < 0.001), compared with those in the adjuvant-only control group. When the trial was repeated using the recombinant antigen cocktail vaccine, no statistically significant differences in mean PRM numbers were observed in cages containing vaccinated or adjuvant-only immunised birds. The roles of antigen-specific antibody levels and duration in providing vaccine-induced and exposure-related protective immunity are discussed.

Laboratory and field evaluations of camptothecin sodium salt against phytophagous mites

BACKGROUND

Camptothecin (CPT), a monoterpene indole alkaloid from Camptotheca acuminate (Nyssaceae), is toxic to some insect pests but insoluble in water. Here we show that an aqueous CPT-Na(+) solution can kill the phytophagous mites Tetranychus urticae (TU), Acaphylla theae (AT) and Brevipalpus obovatus (BO) under laboratory and field conditions.

RESULTS

Modelling of 10 day time-concentration-mortality responses of female adults to 2 mL tower sprays of three CPT-Na(+) dilutions generated LC50 and LT50 values that decreased over post-spray days and sprayed amounts respectively. CPT-Na(+) sprays required to kill 50% BO, TU and AT were 35, 41 and 124 µg mL(-1) on day 1 post-spray, but rapidly decreased to 2.2, 2.5 and 3.6 µg mL(-1) on day 5, and to 0.69, 0.77 and 1.17 µg mL(-1) on day 7 respectively. In summer field trials, a spray rate of 7.5 g CPT-Na(+) ha(-1) provided better control efficacy against TU (81-85%) on cotton or AT (90-93%) and BO (83-88%) in tea gardens than aramite (commercial acaricide) at the labelled rate of 56.25 g ha(-1) . Half of the CPT-Na(+) rate controlled the mites as effectively as aramite.

CONCLUSION

Water-soluble CPT-Na(+) is a promising plant-sourced acaricide to combat wide-spectrum pest mites.

Multiple mutations in the para-sodium channel gene are associated with pyrethroid resistance in Rhipicephalus microplus from the United States and Mexico

BACKGROUND

Acaricide resistant Rhipicephalus microplus populations have become a major problem for many cattle producing areas of the world. Pyrethroid resistance in arthropods is typically associated with mutations in domains I, II, III, and IV of voltage-gated sodium channel genes. In R. microplus, known resistance mutations include a domain II change (C190A) in populations from Australia, Africa, and South America and a domain III mutation (T2134A) that only occurs in Mexico and the U.S.

METHODS

We investigated pyrethroid resistance in cattle fever ticks from Texas and Mexico by estimating resistance levels in field-collected ticks using larval packet discriminating dose (DD) assays and identifying single nucleotide polymorphisms (SNPs) in the para-sodium channel gene that associated with resistance. We then developed qPCR assays for three SNPs and screened a larger set of 1,488 R. microplus ticks, representing 77 field collections and four laboratory strains, for SNP frequency.

RESULTS

We detected resistance SNPs in 21 of 68 U.S. field collections and six of nine Mexico field collections. We expected to identify the domain III SNP (T2134A) at a high frequency; however, we only found it in three U.S. collections. A much more common SNP in the U.S. (detected in 19 of 21 field collections) was the C190A domain II mutation, which has never before been reported from North America. We also discovered a novel domain II SNP (T170C) in ten U.S. and two Mexico field collections. The T170C transition mutation has previously been associated with extreme levels of resistance (super-knockdown resistance) in insects. We found a significant correlation (r = 0.81) between the proportion of individuals in field collections that carried any two resistance SNPs and the percent survivorship of F1 larvae from these collections in DD assays. This relationship is accurately predicted by a simple linear regression model (R2 = 0.6635).

CONCLUSIONS

These findings demonstrate that multiple mutations in the para-sodium channel gene independently associate with pyrethroid resistance in R. microplus ticks, which is likely a consequence of human-induced selection.