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

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.

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.

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

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

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

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

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.

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.

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.

De novo transcriptome sequencing of the northern fowl mite, Ornithonyssus sylviarum, shed light on parasitiform poultry mites evolution and its chemoreceptor repertoires

The northern fowl mite (NFM), Ornithonyssus sylviarum, and the poultry red mite (PRM), Dermanyssus gallinae, are the most serious pests of poultry, both of which have an expanding global prevalence. Research on NFM has been constrained by a lack of genomic and transcriptomic data. Here, we report and analyze the first global transcriptome data across all mite live stages and sexes. A total of 28,999 unigenes were assembled, of which 19,750 (68.10%) were annotated using seven functional databases. The biological function of these unigenes was classified using the GO, KOG, and KEGG databases. To gain insight into the chemosensory receptor-based system of parasitiform mites, we furthermore assessed the gene repertoire of gustatory receptors (GRs) and ionotropic receptors (IRs), both of which encode putative ligand-gated ion channel proteins. While these receptors are well characterized in insect model species, our understanding of chemosensory detection in mites and ticks is in its infancy. To address this paucity of data, we identified 9 IR/iGluRs and 2 GRs genes by analyzing transcriptome data in the NFM, while 9 GRs and 41 IR/iGluRs genes were annotated in the PRM genome. Taken together, the transcriptomic and genomic annotation of these two species provide a valuable reference for studies of parasitiform mites and also help to understand how chemosensory gene family expansion/contraction events may have been reshaped by an obligate parasitic lifestyle compared with their free-living closest relatives. Future studies should include additional species to validate this observation and functional characterization of the identified proteins as a step forward in identifying tools for controlling these poultry pests.

In vitro evaluation of a cysteine protease from poultry red mites, Demanyssus gallinae, as a vaccine antigen for chickens

Poultry red mites (PRMs, Dermanyssus gallinae) are hematophagous ectoparasites that negatively affect egg production, which causes serious economic losses to the poultry industry worldwide. Currently, the emergence of acaricide-resistant PRMs has impeded PRM control in poultry farms. Several alternatives for acaricide use have been described for managing PRM-caused problems. Vaccination is among the methods for controlling PRMs in poultry houses. Currently, several candidates for vaccine antigens have been identified. This study identified a cysteine protease, Deg-CPR-2, which differs from 2 other previously reported cysteine proteases in PRMs, from previously obtained data from RNA-sequencing (RNA-seq) analysis. We investigated the characteristics of Deg-CPR-2 and assessed its efficacy as a vaccine antigen in vitro. Phylogenetic analysis revealed that Deg-CPR-2 belonged to a different cluster from those of other cysteine proteases in PRMs. This cluster also included cathepsin L-like proteases, enzymes thought to be involved in hemoglobin digestion in ticks. Expression analysis revealed Deg-CPR-2 expression in midguts and all the life-stages; however, there were differences in the expression levels across the life-stages. The enzyme activity of recombinant Deg-CPR-2 was inhibited in the presence of a cysteine protease inhibitor, which suggests that Deg-CPR-2 functions as a cysteine protease in PRMs. Finally, there was an in vitro increase in the mortality of PRMs, mainly protonymphs that were artificially fed with plasma from chickens immunized with Deg-CPR-2. These findings suggest that Deg-CPR-2 may contribute to protein digestion in the midgut of PRMs and is crucially involved in physiological processes in PRMs. Additionally, immunization with Deg-CPR-2 may reduce the number of protonymphs, and Deg-CPR-2 should be considered as a candidate antigen for anti-PRM vaccine development.

Acaricidal Activity of Annonaceae Plants for Dermanyssus gallinae (Acari: Dermanyssidae) and Metabolomic Profile by HPLC-MS/MS

The poultry red mite Dermanyssus gallinae (De Geer) is the most important haematophagous ectoparasite in the poultry industry. The use of synthetic acaricides for this control is presenting risks related to human food. In this sense, plant secondary metabolites are promising for controlling this pest. Thus, this study aimed to evaluate the acaricidal activity of Duguetia lanceolata A.St.-Hil. (stem bark), Xylopia emarginata Mart. (stem bark), and Xylopia sericea A.St.-Hil. (stem bark and fruits) against D. gallinae. Additionally, the secondary metabolite profile of the X. emarginata was analysed by UFLC-DAD-ESI(+)-MS/MS (micrOTOF-QII) and data analysis was performed using the Molecular Networking. In a topical application test, all plant species tested showed bioactivity, in that order of toxicity with the respective probability survival: X. emarginata (stem bark) (0.28) > X. sericea (stem barks) (0.35) > X. sericea (fruits) and D. lanceolata (stem bark) (0.47). The most promising results were found for X. emarginata (LC₅₀ = 331.769 μg/cm²). It is noteworthy that the LC₅₀ of the insecticide cypermethrin was 1234.4 μg/cm², which was 73% higher than that of X. emarginata. The metabolomic profile of X. emarginata revealed the presence of alkaloids, amides, terpenoids, and phenolic compounds. This is the first report of X. emarginata acaricidal activity against D. gallinae and exploratory chemical analysis by untargeted metabolomics and the molecular network of this plant.

Evaluation of in-house factors affecting the population distribution of Dermanyssus gallinae in cage and backyard rearing systems by using a modified monitoring method

Dermanyssus gallinae (poultry red mite, PRM) is a main ectoparasite of poultry that represents a serious economic threat to all farming systems, including cages and backyard flocks. In recent years, economic losses associated with this ectoparasite have progressively increased, mainly because of the lack of information regarding its population dynamics and appropriate control methods. In this study, we used a modified monitoring method to examine the in-house factors affecting the population density of D. gallinae. PRMs have been found in all poultry houses examined in Turkey. The largest population was detected in the front and back parts of the middle rows in cage systems as well as in perches in backyard systems. Relative humidity, light, and temperature might be the most affecting factors on the mite distribution inside the poultry houses. Besides, the mite populations are influenced mainly by the last (chemical) treatment date and the construction materials of the building. Dermanyssus gallinae were found to be the most dominant mite species (98.9%), followed by Cheyletus sp. (Cheyletidae); also some Acaridae (Tyrophagus spp.) and Oribatida were identified. Hence, further research on Cheyletus sp. is required to elucidate their predatory potential and develop future control strategies. This study contributes to understanding the PRM population behavior in poultry houses as well as their monitoring and control methods, which are key components in the appropriate application of integrated pest management programs.

Assessment of fluralaner as a treatment in controlling Dermanyssus gallinae infestation on commercial layer farms and the potential for resulting benefits of improved bird welfare and productivity

Background

Poultry red mite (PRM) (Dermanyssus gallinae) infestations are a cause of anaemia, impaired productivity and stress-related behaviours linked to reduced hen welfare. A study investigated the potential health, welfare and productivity benefits following fluralaner treatment to eliminate PRM from infested hens.

Methods

A PRM-infested layer house was selected on a free-range farm (5400 hens) and an aviary farm (42,400 hens). Fluralaner (Exzolt^®; 0.5 mg/kg body weight) was administered twice, 7 days apart (Weeks 0 and 1), via drinking water. Mite populations were monitored by traps. Cameras recorded nighttime hen behaviours weekly, pre- and post-treatment. On the free-range farm, daytime behaviours were also recorded weekly. For pre- and post-treatment corticosterone assessments, eggs were randomly collected on both farms, and blood samples were collected from 50 randomly selected aviary farm hens. Production parameters were assessed using farm records.

Results

Throughout the post-treatment period, fluralaner efficacy against PRM was > 99% on both farms. On the aviary and free-range farms, treatment was followed by significant nighttime increases in the proportion of resting hens (P < 0.0001; P = 0.0175, respectively). Significant post-treatment versus pre-treatment nighttime reductions were observed in head shaking (aviary, P < 0.0001; free-range P = 0.0233) and preening (P = 0.0032; P = 0.0018) and on the aviary farm in bouts of body shaking (P = 0.0108), vertical wing shaking (P = 0.0002), head scratching (P = 0.0335), and gentle feather pecking (P < 0.0001). On the free-range farm there were significant daytime reductions in head scratching (P < 0.0001), head shaking (P = 0.0492) and preening (P = 0.0012). Relative to standard production parameters, no differences were detected on the aviary farm, but on the free-range farm the laying rate decline with increasing age was less than expected and the increase in egg weight greater than expected. Post-treatment increases in egg and plasma corticosterone were suggestive of stress factors in addition to mite infestation. Red blood cell counts and haematocrit increased following treatment.

Conclusion

Fluralaner treatment eliminated mite challenge, leading to improved hen welfare and health, based on reductions in stress-related behaviours and restoration of the anaemia-inducing effects of mite blood feeding.

Case of Human Infestation with Dermanyssus gallinae (Poultry Red Mite) from Swallows (Hirundinidae)

Dermanyssus gallinae (the poultry red mite, PRM) is an important ectoparasite in the laying hen industry. PRM can also infest humans, causing gamasoidosis, which is manifested as skin lesions characterized by rash and itching. Recently, there has been an increase in the reported number of human infestation cases with D. gallinae, mostly associated with the proliferation of pigeons in cities where they build their nests. The human form of the disease has not been linked to swallows (Hirundinidae) before. In this report, we describe an incident of human gamasoidosis linked to a nest of swallows built on the window ledge of an apartment in the island of Kefalonia, Greece. Mites were identified as D. gallinae using morphological keys and amplifying the Cytochrome C oxidase subunit I (COI) gene by PCR. Bayesian phylogenetic analysis and median-joining network supported the identification of three PRM haplogroups and the haplotype isolated from swallows was identical to three PRM sequences isolated from hens in Portugal. The patient was treated with topical corticosteroids, while the house was sprayed with deltamethrin. After one week, the mites disappeared and clinical symptoms subsided. The current study is the first report of human gamasoidosis from PRM found in swallows’ nest.

Selection of reference genes for quantitative PCR analysis in poultry red mite (Dermanyssus gallinae)

Poultry red mites (PRMs, Dermanyssus gallinae) are harmful ectoparasites that affect farmed chickens and cause serious economic losses in the poultry industry worldwide. Acaricides are used for PRM control; however, some PRMs have developed acaricide-resistant properties, which have indicated the need for different approaches for PRM control. Therefore, it is necessary to elucidate the biological status of PRMs to develop alternative PRM control strategies. Quantitative polymerase chain reaction (qPCR) allows analysis of the biological status at the transcript level. However, reference genes are preferable for accurate comparison of expression level changes given the large variation in the quality of the PRM samples collected in each farm. This study aimed to identify candidate reference genes with stable expression levels in the different blood feeding states and life stages of PRMs. First, we selected candidates based on the following criteria: sufficient expression intensity and no significant expression difference between fed and starved states. We selected and characterized seven candidate reference genes. Among them, we evaluated the gene expression stability between the starved and fed states using RefFinder; moreover, we compared their expression levels in each life-stage and identified two reference genes, Elongation factor 1-alpha (ELF1A)-like and apolipophorins-like. Finally, we evaluated the utility of the candidates as reference genes, and the use of ELF1A-like and apolipophorins-like successfully normalized ATP synthase subunit g -like gene expression. Thus, ELF1A-like and apolipophorins-like could be suitable reference genes in PRMs.

Characterisation of a cysteine protease from poultry red mites and its potential use as a vaccine for chickens

Poultry red mites (PRMs, Dermanyssus gallinae) are ectoparasites that negatively affect farmed chickens, leading to serious economic losses worldwide. Acaricides have been used to control PRMs in poultry houses. However, some PRMs have developed resistance to acaricides, and therefore different approaches are required to manage the problems caused by PRMs. Vaccination of chickens is one of the methods being considered to reduce the number of PRMs in poultry houses. In a previous study, a cysteine protease, Deg-CPR-1, was identified as a candidate vaccine against PRMs distributed in Europe. In this study, we investigated the characteristics of Deg-CPR-1. A phylogenetic analysis revealed that Deg-CPR-1 is closely related to the digestive cysteine proteases of other mite species, and it was classified into a cluster different from that of chicken cathepsins. Deg-CPR-1 of PRMs in Japan has an amino acid substitution compared with that of PRMs in Europe, but it showed efficacy as a vaccine, consistent with previous findings. Deg-CPR-1 exhibited cathepsin L-like enzyme activity. In addition, the Deg-CPR-1 mRNA was expressed in the midgut and in all stages of PRMs that feed on blood. These results imply that Deg-CPR-1 in the midgut may have important functions in physiological processes, and the inhibition of its expression may contribute to the efficacy of a Deg-CPR-1-based vaccine. Further research is required to fully understand the mechanisms of vaccine efficacy.

Possibilities for IPM Strategies in European Laying Hen Farms for Improved Control of the Poultry Red Mite (Dermanyssus gallinae): Details and State of Affairs

The Poultry Red Mite (PRM), Dermanyssus gallinae, is a major threat to the poultry industry worldwide, causing serious problems to animal health and welfare, and huge economic losses. Controlling PRM infestations is very challenging. Conventionally, D. gallinae is treated with synthetic acaricides, but the particular lifestyle of the mite (most of the time spent off the host) makes the efficacy of acaracide sprays often unsatisfactory, as sprays reach only a small part of the population. Moreover, many acaricides have been unlicensed due to human consumer and safety regulations and mites have become resistant to them. A promising course of action is Integrated Pest Management (IPM), which is sustainable for animals, humans and the environment. It combines eight different steps, in which prevention of introduction and monitoring of the pest are key. Further, it focusses on non-chemical treatments, with chemicals only being used as a last resort. Whereas IPM is already widely applied in horticulture, its application is still in its infancy to control D. gallinae in layer houses. This review presents the currently-available possibilities for control of D. gallinae in layer houses for each of the eight IPM steps, including monitoring techniques, established and emerging non-chemical treatments, and the strategic use of chemicals. As such, it provides a needed baseline for future development of specific IPM strategies, which will allow efficient and sustainable control of D. gallinae in poultry farms.

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.

Evidence of vector borne transmission of Salmonella enterica enterica serovar Gallinarum and fowl typhoid disease mediated by the poultry red mite, Dermanyssus gallinae (De Geer, 1778)

BACKGROUND

The poultry red mite Dermanyssus gallinae (De Geer, 1778) is a major ectoparasite of poultry. Infestations are found in most laying hen farms in Europe, and breeder flocks have also been reported to be affected. Mite infestation has detrimental effects on animal welfare, it causes significant economic losses, and, additionally, D. gallinae is often considered as a vector for pathogens. Despite suspicion of a close relationship between the poultry red mite and Salmonella enterica enterica serovar Gallinarum biovar Gallinarum (serovar Gallinarum), the causative agent of fowl typhoid disease (FT), there has been no definitive proof of mite-mediated transmission. Therefore, an investigation was conducted to determine if D. gallinae-mediated transmission of serovar Gallinarum could be demonstrated among four different hen groups.

METHODS

Two groups of 8 hens (A and B) were experimentally infected with serovar Gallinarum in two isolators. After 7 days, when birds showed signs of FT, about 25,000 mites were introduced. After 3 days, mites were harvested and used to infest two other hen groups of 8 (C and D), in two separate isolators. The health status of hens was constantly monitored; detection and quantification of serovar Gallinarum were performed by PCR and qPCR from mites and organs of dead hens. The maximum likelihood estimation of the infection rate and mite vectorial capacity were calculated.

RESULTS

Clinical disease was observed in groups infected with serovar Gallinarum (A and B) and in hens of groups C and D infested with mites harvested from the isolators containing groups A and B. In all four groups, serovar Gallinarum was detected from liver, spleen, ovary, and cecum of hens, thus confirming the diagnosis of FT. Mite analysis demonstrated the presence of the pathogen, with an estimated infection rate ranging between 13.72 and 55.21 infected per thousand mites. Vectorial capacity was estimated to be 73.79.

CONCLUSIONS

Mites harvested from birds infected with serovar Gallinarum were shown to carry the mite, and then to transfer serovar Gallinarum to isolated groups of pathogen-free birds that subsequently showed signs of FT. Mite vectorial capacity was high, demonstrating that D. gallinae should be considered an effective vector of FT.

De novo assembly and discovery of genes related to blood digestion in the transcriptome of Dermanyssus gallinae (Acari: Dermanyssidae)

Dermanyssus gallinae is an economically important blood-feeding ectoparasite affecting layer chicken farms in many countries. Similar to other blood-feeding arthropods, the blood-meal digestion plays a key role in the survival and reproduction of D. gallinae. The knowledge of the genes involved in blood digestion processes may provide new targets for drug and vaccine against the red mites. In the present study, we sequenced and de novo assembled the transcriptomes of unfed and fed adult red mites using Illumina RNA sequencing (RNA-seq) technology. Up to 40,506 unigenes were assembled, and 13,018 unigenes were identified and annotated. GO analysis of the annotated unigenes clustered into three main GO terms. The dominant GO terms of biological processes were cellular process and metabolic process, the prevailing GO terms of the cellular component were cell part and membrane part, and the dominant GO terms of molecular functions were catalytic and binding activities. Up to 6,443 annotated sequences were assigned to 246 active pathways by KEGG analysis. Differentially expressed genes (DEGs) analysis identified 2,877 unigenes with upregulated 2,094 and downregulated 783 in fed female mites compared with unfed female mites. The biological function of these DEGs was further investigated using the KEGG and GO databases. The upregulated DEGs were potentially involved in nutrient metabolism, highlighting their importance in red mite biology. Quantitative reverse transcription real-time PCR (qRT-PCR) validated that the expression levels of the selected six upregulated DEGs were consistent with those in RNA-seq, indicating that the transcriptomic data are reliable. The present study provides valuable and fundamental knowledge that improves our understanding of the physiology of D. gallinae digestion at a molecular level. Moreover, these transcriptomic data will facilitate the identification of novel function genes and candidate antigens for the development of effective vaccines or drug targets to control 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.

Molecular characterization and genetic diversity of Ornithonyssus sylviarum in chickens (Gallus gallus) from Hainan Island, China

BACKGROUND

The northern fowl mite (NFM), Ornithonyssus sylviarum, is an obligatory hematophagous ectoparasite of birds and one of the most important pests in the poultry industry on several continents. Although NFM poses a serious problem, it remains a neglected pest of poultry in China and other Asian countries. Therefore, a molecular analysis was conducted to provide baseline information on the occurrence, genetic diversity and emergence of NFM in poultry farms from China.

METHODS

This study focused on morphological description and identification of adults based on electron microscopy, molecular sequencing of the mitochondrial cox1 gene and phylogenetic analysis. We have also used the DNA sequences of the cox1 gene to study the genetic diversity, population structure and demographic history. The neutrality tests were used to analyze signatures of historical demographic events.

RESULTS

The mites collected were identified as the northern fowl mite Ornithonyssus sylviarum based on external morphological characterization using electron microscopy. Molecular analysis using a 756-bp long partial fragment of the cox1 gene revealed 99-100% sequence identity with NFM and phylogenetic inferences showed a bootstrap value of 99% indicating a well-supported monophyletic relationship. Molecular diversity indices showed high levels of haplotype diversity dominated by private haplotypes, but low nucleotide divergence between haplotypes. The Tajima's D test and Fu's Fs test showed negative value, indicating deviations from neutrality and both suggested recent population expansion of mite populations supported by a star-like topology of the isolates in the network analysis. Our genetic data are consistent with a single introduction of NFM infestations and the spread of NFM infestation in Hainan poultry farms and a private haplotype dominance, which suggest that infestations are recycled within the farms and transmission routes are limited between farms.

CONCLUSIONS

To our knowledge, this is the first time a molecular report of NFM in chicken from China including other Asian countries using DNA barcoding. The findings have potential implications with respect to understanding the transmission patterns, emergence and populations trends of parasitic infestations of poultry farms that will help for setting the parameters for integrated pest management (IPM) tactics against mite infestations.

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.

Production losses in laying hens during infestation with the poultry red mite Dermanyssus gallinae

A research centre with 30,568 laying hens, kept in enriched cages and in aviaries, had become naturally infested with poultry red mites (PRM) in 32 of its 48 bird units. Therefore, at the age of 52 weeks all hens were treated with fluralaner through the drinking water. After this treatment, PRM were no longer observed. As all birds were of the same age, and since production figures were measured daily in all 48 units, this offered a unique opportunity to examine how PRM had affected performance. Statistical analyses were done to compare the evolution of production data from the pre-treatment to the post-treatment period in units that were visually free of PRM or infested with PRM to different levels. Production standards provided by the breeding organizations were used as a reference. The results demonstrated significant posttreatment increases of laying percentage, egg weight, egg mass, percentage first choice eggs, feed intake and body weight in heavily infested hens of one or both housing systems, as compared to the non-infested controls. These data confirm that PRM infestations can impact the main performance traits related to profitability of laying hen farms as well as the hens' general condition.

The residue levels of spinosad and abamectin in eggs and tissues of laying hens following spray application

Spinosad (SPN) and abamectin (ABM) are used in poultry premises to control external parasites including red mites (Dermanyssus gallinae). This study aimed to determine levels of SPN (spinosyn A + spinosyn D) and ABM residues in egg and edible tissues of laying hens following spray application. A total of 36 laying hens were divided into four groups of nine birds each, and they were kept in individual cages. Two different concentrations of SPN (2 and 4 g/l) and ABM (0.025 and 0.033 g/l) were applied in stocked and empty cages, respectively. Eggs were collected individually for 30 days. All hens were sacrificed at day 30 post-treatment, and tissue samples (liver, breast muscle, fat and skin) were collected. The residue levels in eggs and tissues were determined by high pressure liquid chromatography. ABM residues were not detectable in egg samples. SPN residues in eggs and residues of both ABM and SPN in liver, muscle and fat were under the maximum residue limits (MRLs) following low and high concentration applications. However, although the MRLs have not been established for SPN and ABM in skin tissue of chicken, residues in the skin detected at the low and high concentrations were greater than the MRLs for other edible tissues (except fat tissue) indicating that a withdrawal period would be necessary for the skin tissue after ABM and SPN use in laying hens.

Darkness increases the population growth rate of the poultry red mite Dermanyssus gallinae

BACKGROUND

The poultry red mite (PRM), Dermanyssus gallinae, is one of the most economically deleterious ectoparasites affecting egg-laying hens worldwide. It may be possible to control D. gallinae populations by manipulating lighting regimes within poultry units. However, no studies have clearly shown the effects of darkness on the population growth rate of D. gallinae.

METHODS

The effect of darkness on the population growth rate of D. gallinae was investigated, together with the first description of the molecular identity of the mite from China. Mite variables under two lighting regimens (1:23 h L:D and 12:12 h L:D) were compared, including number of mites and eggs, survival and feeding rates, engorgement, oviposition, hatchability and the life-cycle of D. gallinae.

RESULTS

The results showed that the number of mites (13,763 ± 956) and eggs (5424 ± 317) in the rearing system with prolonged darkness of 1:23 h L:D at 4th week were 2.4- and 3.6-fold higher than those under a conventional lighting regimen of 12:12 h L:D, respectively. The feeding rates of mites under prolonged darkness ranged from 36.7 ± 1.1% to 52.0 ± 7.0%, which were significantly higher than those under conventional lighting regimen (ranging from 22.6 ± 1.9% to 37.3 ± 1.6%). The mean weight of engorged females (0.26 ± 0.01 mg) and the mean number of eggs per female (on average 5.87 ± 0.36) under prolonged darkness were significantly higher than those under conventional lighting regimen (0.22 ± 0.01 mg and 3.62 ± 0.31, respectively). However, the survival rate ranging from 98.07 ± 0.10% to 98.93 ± 0.19%, hatchability of 97.93 ± 0.01% and the life-cycle of D. gallinae (9 days) was not affected by the lighting period.

CONCLUSIONS

Our findings demonstrated that prolonged darkness significantly promoted the proliferation levels of D. gallinae, resulting in increased number of mites and eggs in the rearing system. The promoted population growth of D. gallinae was found to be related to the increased feeding rate, engorgement level and oviposition level of mites under prolonged darkness. The egg hatchability, the survival rates and the duration of life-cycle of D. gallinae were not affected by the light regimes.

The Golden Egg: Nutritional Value, Bioactivities, and Emerging Benefits for Human Health

Egg is an encapsulated source of macro and micronutrients that meet all requirements to support embryonic development until hatching. The perfect balance and diversity in its nutrients along with its high digestibility and its affordable price has put the egg in the spotlight as a basic food for humans. However, egg still has to face many years of nutritionist recommendations aiming at restricting egg consumption to limit cardiovascular diseases incidence. Most experimental, clinical, and epidemiologic studies concluded that there was no evidence of a correlation between dietary cholesterol brought by eggs and an increase in plasma total-cholesterol. Egg remains a food product of high nutritional quality for adults including elderly people and children and is extensively consumed worldwide. In parallel, there is compelling evidence that egg also contains many and still-unexplored bioactive compounds, which may be of high interest in preventing/curing diseases. This review will give an overview of (1) the main nutritional characteristics of chicken egg, (2) emerging data related to egg bioactive compounds, and (3) some factors affecting egg composition including a comparison of nutritional value between eggs from various domestic species.