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

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

Avian mite dermatitis: Diagnostic challenges and unmet needs.

The avian mite Dermanyssus gallinae (poultry red mite, PRM) is of major economic and veterinary importance for the poultry and egg industry worldwide. The accumulating reports on the opportunistic nonavian feeding of D. gallinae raise concerns on PRM host expansion. However, the consequent threats to human health remain largely unclear. PRM infestation in humans is usually manifested as a local or generalized noncharacteristic skin reaction referred to as gamasoidosis. This report presents the current state of the art and the new developments on PRM-associated dermatitis, sharing neither the authors' personal experience nor focusing on differential diagnosis. Specifically, it reflects the outcome of the critical assessment of the available literature by European medical and veterinary experts in the field under the "One Health" approach.

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

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

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

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

Significance and control of the poultry red mite, Dermanyssus gallinae.

The poultry red mite, Dermanyssus gallinae, poses a significant threat to poultry production and hen health in many parts of the world. With D. gallinae increasingly suspected of being a disease vector, and reports indicating that attacks on alternative hosts, including humans, are becoming more common, the economic importance of this pest has increased greatly. As poultry production moves away from conventional cage systems in many parts of the world, D. gallinae is likely to become more abundant and difficult to control. Control remains dominated by the use of synthetic acaricides, although resistance and treatment failure are widely reported. Alternative control measures are emerging from research devoted to D. gallinae and its management. These alternative control measures are beginning to penetrate the market, although many remain at the precommercial stage. This review compiles the expanding body of research on D. gallinae and assesses options for its current and future control. We conclude that significant advances in D. gallinae control are most likely to come through an integrated approach adopting recent research into existing and novel control strategies; this is being combined with improved monitoring and modeling to better inform treatment interventions.

Molecular characterization and phylogenetic inferences of Dermanyssus gallinae isolates in Italy within an European framework.

In order to investigate the genetic relationships between Dermanyssus gallinae (Metastigmata: Dermanyssidae) (de Geer) isolates from poultry farms in Italy and other European countries, phylogenetic analysis was performed using a portion of the cytochrome c oxidase subunit 1 (cox1) gene of the mitochondrial DNA and the internal transcribed spacers (ITS1+5.8S+ITS2) of the ribosomal DNA. A total of 360 cox1 sequences and 360 ITS+ sequences were obtained from mites collected on 24 different poultry farms in 10 different regions of Northern and Southern Italy. Phylogenetic analysis of the cox1 sequences resulted in the clustering of two groups (A and B), whereas phylogenetic analysis of the ITS+ resulted in largely unresolved clusters. Knowledge of the genetic make-up of mite populations within countries, together with comparative analyses of D. gallinae isolates from different countries, will provide better understanding of the population dynamics of D. gallinae. This will also allow the identification of genetic markers of emerging acaricide resistance and the development of alternative strategies for the prevention and treatment of infestations.

Chlamydia psittaci infection in canaries heavily infested by Dermanyssus gallinae.

Dermanyssus gallinae is a haematophagous ectoparasite responsible for anemia, weight loss, dermatitis and a decrease in egg production. Dermanyssus gallinae may play a role in the modulation of the host immune system, maybe predisposing the host to some bacterial infections such as chlamydiosis. This is an important zoonosis. Humans are exposed to Chlamydia psittaci through inhalation of the agent dispersed from the infected birds. In this study, a syndrome observed in an aviary of canaries was investigated. A heavy infestation by D. gallinae was reported. Simultaneously, a C. psittaci infection was molecularly confirmed in the canaries. Combined therapy was applied successfully. The association of C. psittaci with the examined mites has been confirmed. Therefore, we think that D. gallinae have played a role in the spreading of C. psittaci infection among the canaries. Moreover, D. gallinae could have played an important role predisposing the canaries to the development of chlamydiosis, by inducing anemia and debilitation. The control of mites in the aviaries may represent a crucial step for the prevention of important infection such as chlamydiosis in birds and humans.

Environmental interactions with the toxicity of plant essential oils to the poultry red mite Dermanyssus gallinae.

The toxicity of a range of plant essential oils to the poultry red mite, Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae), a serious ectoparasitic pest of laying hens throughout Europe and elsewhere, was assessed in the laboratory. Dermanyssus gallinae may cause losses in egg production, anaemia and, in extreme cases, death of hens. With changes in legislation and consumer demand, alternatives to synthetic acaricides are needed to manage this pest. Fifty plant essential oils were selected for their toxicity to arthropods reported in the literature. Twenty-four of these essential oils were found to kill > 75% of adult D. gallinae in contact toxicity tests over a 24-h period at a rate of 0.21 mg/cm(2). Subsequent testing at lower rates showed that the essential oils of cade, manuka and thyme were especially toxic to adult D. gallinae. The toxicity of the seven most acaricidal essential oils was found to be stable at different temperatures likely to be encountered in commercial poultry housing (15 degrees C, 22 degrees C and 29 degrees C), although results suggest that humidity and dust might influence the toxicity of some of the oils tested. The toxicity of clove bud essential oil to D. gallinae, for example, was increased at high humidity and dust levels compared with ambient levels. The results suggest that certain essential oils may make effective botanical pesticides for use against D. gallinae, although it is likely that issues relating to the consistency of the toxic effect of some oils will determine which oils will be most effective in practice.

Toxicity of plant essential oils to different life stages of the poultry red mite, Dermanyssus gallinae, and non-target invertebrates.

Seven essential oils with potential as acaricides for use against the poultry red mite, Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae), were selected for study. These products (essential oils of manuka, cade, pennyroyal, thyme, garlic, clove bud and cinnamon bark) were deployed against different life stages of D. gallinae in laboratory tests at the (lethal concentration) LC(50) level for adult mites. For all essential oils tested, toxicity to D. gallinae juveniles was as high as toxicity to adults, if not higher. However, at the LC(50) level determined for adults, some oils were ineffective in preventing hatching of D. gallinae eggs. The essential oils were also tested under laboratory conditions at their LC(90) levels for D. gallinae adults on two model non-target species, the brine shrimp, Artemia salina (L.), and the mealworm beetle, Tenebrio molitor (L.). Results showed that not all essential oils were as toxic to A. salina and T. molitor as they were to D. gallinae, suggesting that it may be possible to select certain oils for development as acaricides against D. gallinae that would have minimal impact on non-target organisms. However, the level of toxicity to A. salina and T. molitor was not consistent across the selected essential oils.

Comparison of synthetic membranes in the development of an in vitro feeding system for Dermanyssus gallinae.

Although artificial feeding models for the poultry red mite (Dermanyssus gallinae) most frequently use biological membranes consisting of day-old chick skin, there are ethical considerations associated with the use of skin. The few studies reported in the literature that have investigated the use of synthetic membranes to feed D. gallinae in vitro have reported limited success. The current study describes an investigation into the use of synthetic membranes made from either Nescofilm or rayon and silicone, used either alone or in combination with different feather or skin extracts, as well as the use of capillary tubes. In all, 12 different treatments were used, and the feeding rate of D. gallinae was compared to that of day-old chick skin. Allowing mites to feed on a membrane consisting of Nescofilm with a skin extract resulted in the highest proportion of mites feeding (32.3%), which was not significantly different to the feeding rate of mites on day-old chick skin (38.8%). This study confirms that synthetic membranes can be used to feed D. gallinae artificially. Further optimization of the membrane and mite storage conditions is still necessary, but the study demonstrates a proof of concept.

Repellence of plant essential oils to Dermanyssus gallinae and toxicity to the non-target invertebrate Tenebrio molitor.

With changes in legislation and consumer demand, alternatives to synthetic acaricides to manage the poultry red mite Dermanyssus gallinae (De Geer) in laying hen flocks are increasingly needed. These mites may cause losses in egg production, anaemia and even death of hens. It may be possible to use plant-derived products as D. gallinae repellents, especially if such products have a minimal impact on non-target organisms. An experiment was conducted with D. gallinae to assess the repellence of a range of plant essential oils, previously found to be of varying toxicity (relatively highly toxic to non-toxic) to this pest. Experiments were also undertaken to assess the toxicity of these products to mealworm beetles (Tenebrio molitor L.), a non-target invertebrate typical of poultry production systems. Results showed that all seven essential oils tested (manuka, thyme, palmarosa, caraway, spearmint, black pepper and juniper leaf) were repellent to D. gallinae at 0.14mg oil/cm(3) (initial concentration) during the first 2 days of study. Thyme essential oil appeared to be the most effective, where repellence lasted until the end of the study period (13 days). At the same concentration toxicity to T. molitor differed, with essential oils of palmarosa and manuka being no more toxic to adult beetles than the control. There was neither a significant association between the rank toxicity and repellence of oils to D. gallinae, nor the toxicity of oils to D. gallinae (as previously determined) and T. molitor.

Mode of action and variability in efficacy of plant essential oils showing toxicity against the poultry red mite, Dermanyssus gallinae.

This paper describes a series of experiments to examine the mode of action and toxicity of three plant essential oils (thyme, manuka and pennyroyal) to the poultry red mite, Dermanyssus gallinae (De Geer), a serious ectoparasitic pest of laying hens. All three oils were found to be toxic to D. gallinae in laboratory tests with LC(50), LC(90) and LC(99) values below 0.05, 0.20 and 0.30mg/cm(3), respectively, suggesting that these products may make for effective acaricides against this pest. Further experiments demonstrated that when mites were exposed to only the vapour phase of the essential oil without contact with the oil itself, mortality was consistently higher in closed arenas than in arenas open to the surrounding environment, or in control arenas. This suggests that all three essential oils were toxic to D. gallinae by fumigant action. In addition, in an experiment where mites were allowed contact with the essential oil in either open or closed arenas, mortality was always reduced in the open arenas where this was comparable to control mortality for thyme and pennyroyal essential oil treatments. This supports the findings of the previous experiment and also suggests that, with the possible exception of manuka, the selected essential oils were not toxic to D. gallinae on contact. Statistical comparisons were made between the toxicity of the selected essential oils to D. gallinae in the current work and in a previous study conducted in the same laboratory. The results demonstrated considerable variation in LC(50), LC(90) and LC(99) values. Since both the essential oils and the mites were obtained from identical sources in the two studies, it is hypothesized that this variation resulted from the use of different 'batches' of essential oil, which could have varied in chemistry and hence acaricidal activity.

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

Red mite field populations from seven naturally infested Italian caged laying poultry farms were investigated for their susceptibility to acaricide formulations available on the market, containing amitraz, carbaryl and permethrin. A minimum of 3,000 mites of all stages were collected from each farm and were tested with five acaricide concentrations (5, 10, 20, 50, 100%) plus an untreated control (0%). Field red mite populations were found to be tolerant even with the highest concentrations with carbaryl and permethrin for six (86%) and three (42%) of the investigated farms, respectively (P < 0.05). Furthermore, six (86%) of the investigated farms showed a red mite population susceptible to amitraz at any concentration. Out of the seven field populations tested with amitraz, one population is becoming less tolerant whereas another was the most tolerant to carbaryl and permethrin at any concentration. Data show that the lack of effectiveness of some acaricides is spreading in Europe and call for the adoption of alternative management strategies to avoid development of resistance.

Phylogenetic relationship between Dermanyssus gallinae populations in European countries based on mitochondrial COI gene sequences.

Phylogenetic analysis of Dermanyssus gallinae mites originating from UK, France and Italy was performed using partial amplification of the mitochondrial COI gene. Results showed that UK samples reveal the greatest variation and diversity and are linked to one of the French populations highlighting North-South genetic transitions in European red mite populations. Intra-farm variations between mite samples highlighted the diversity between national populations and possibly its origin from the different chemical strategies used in each country.

Toxicity of geraniol solution in vitro to the poultry red mite, Dermanyssus galinae.

Geraniol is a bioactive component found in Palmarosa essential oil which has previously demonstrated good repellence to cattle ticks, mosquitoes and sand flies. The toxicity of geraniol to Dermanyssus gallinae, the most economically deleterious ectoparasite of laying hens in Europe, was studied in vitro in the laboratory. Exposure of D. gallinae to 0.5, 1 and 2% concentrations of geraniol (equating approximately to 0.02, 0.04 and 0.07 mg/cm2 geraniol, respectively) over a period of 24 hours resulted in 100% mortality of D. gallinae at all doses used.

From population structure to genetically-engineered vectors: new ways to control vector-borne diseases?

Epidemiological studies on vectors and the pathogens they can carry (such as Borrelia burgdorferi) are showing some correlations between infection rates and biodiversity highlighting the "dilution" effects on potential vectors. Meanwhile other studies comparing sympatric small rodent species demonstrated that rodent species transmitting more pathogens are parasitized by more ectoparasite species. Studies on population structure and size have also proven a difference on the intensity of the parasitic infection. Furthermore, preliminary results in genetic improvement in mosquitoes (genetic markers, sexing, and genetic sterilization) will also increase performance as it has already been shown in field applications in developing countries. Recent results have greatly improved the fitness of genetically-modified insects compared to wild type populations with new approaches such as the post-integration elimination of transposon sequences, stabilising any insertion in genetically-modified insects. Encouraging results using the Sterile Insect Technique highlighted some metabolism manipulation to avoid the viability of offspring from released parent insect in the wild. Recent studies on vector symbionts would also bring a new angle in vector control capabilities, while complete DNA sequencing of some arthropods could point out ways to block the deadly impact on animal and human populations. These new potential approaches will improve the levels of control or even in some cases would eradicate vector species and consequently the vector-borne diseases they can transmit. In this paper we review some of the population biology theories, biological control methods, and the genetic techniques that have been published in the last years that are recommended to control for vector-borne diseases.

The influence of 'time since last blood meal' on the toxicity of essential oils to the poultry red mite (Dermanyssus gallinae).

The poultry red mite, Dermanyssus gallinae (De Geer) is a serious ectoparasitic pest of layer hens that can survive for long periods in the poultry house sub-structure without taking a blood meal from its host. The research undertaken in this study found that 'time since last blood meal' had a notable effect on how toxic a selection of plant essential oils were to D. gallinae under laboratory conditions. In general, the essential oils had a greater toxic effect on D. gallinae if mites had been starved of a blood meal for around 3 weeks, than if they had been more recently fed 3-13 days prior to tests. This result was consistent across the four essential oils used (thyme, palmarosa, caraway and juniper leaf). This suggests that plant essential oils may be of use in management schemes for D. gallinae, particularly if used to sanitise houses between flocks, when mites will have been starved.

Lack of prolonged activity of lavender essential oils as acaricides against the poultry red mite (Dermanyssusgallinae) under laboratory conditions.

Managing the poultry red mite, Dermanyssusgallinae (De Geer) by conventional means (i.e., synthetic acaricides) has become increasingly problematic. As a possible alternative, research has identified several plant essential oils that are toxic to D. gallinae. However, essential oils are highly volatile and any acaricidal effect they exert could be short-lived in practice. This study investigated the short-lived toxicity of six lavender essential oils to D. gallinae. In sealed Petri-dishes, mites were exposed to filter papers impregnated with essential oil at a concentration of 0.14mg/cm(3). When filter papers were used immediately after impregnation, 66-90% D.gallinae mortality was observed after 24h, depending upon the essential oil used. If impregnated filter papers were left in a fume cupboard for 24h prior to use, mortality rates of D.gallinae fell to 11% or less.

Transcription Factors as a Target for Vaccination Against Ticks and Mites.

Ticks and mites are well-known ectoparasites as potential vectors for numerous bacteria, viruses, and parasites. Many being blood feeders add to physiological deterioration, morbidity, and mortality of their vertebrate hosts. To control them, transcription factors have been identified and studied in their role to sustain such arthropod pests. This paper summarizes some of the work done on those factors involved during blood feeding, reproduction, or when interacting with their pathogens and symbiont populations. Any transcription factor supporting the equilibrium developed by the ticks/mites could become a potential target for new control methods to prevent some of their key physiological functions.