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.

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.

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.

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.

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.

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.

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.

Comparing terpenes from plant essential oils as pesticides for the poultry red mite (Dermanyssus gallinae).

Resistance to conventional synthetic pesticides has been widely reported in ticks, parasitic mites and other pests of veterinary and medical significance. New and novel approaches to manage these pests are therefore needed to ensure efficient control programmes that can be implemented now and in the future. Recent research in this area has focused on the pesticidal potential of plant essential oils. These products are attractive as pesticide candidates on the grounds of low mammalian toxicity, short environmental persistence and complex chemistries (limiting the development of pest resistance against them). Although issues may exist concerning reliability in efficacy of essential oils, these may be overcome by identifying and developing bioactive oil components for use in pest management. In the current work, three such components (terpenes) found in essential oils (eugenol, geraniol and citral) were tested against the poultry red mite Dermanyssus gallinae. All provided 100% mortality in toxicity tests when undiluted. Even at 1% of this dose, eugenol was 20% effective against experimental pest populations, although the remaining terpenes were largely ineffective at this concentration.

Laboratory screening of potential predators of the poultry red mite (Dermanyssus gallinae) and assessment of Hypoaspis miles performance under varying biotic and abiotic conditions.

The poultry red mite, Dermanyssus gallinae (De Geer), is the most important ectoparasitic pest of layer hens worldwide and difficult to control through 'conventional' synthetic acaricides. The present study aimed to identify a suitable predator of D. gallinae that could potentially form the basis of biological control in commercial poultry systems. From four selected predatory mite species (Hypoaspis miles (Berlese), Hypoaspis aculeifer (Canestrini), Amblyseius degenerans (Berlese) and Phytoseiulus persimilis (Athias-Henriot)), Hypoaspis mites demonstrated the greatest potential as predators of D. gallinae. Experiments were also conducted to assess the effect of environmental (temperature and dust), physical (presence of harbourages) and biological (presence of alternative prey) factors on the predatory efficacy of H. miles. Predation of D. gallinae per se was observed under all conditions tested, though was found to be temperature-dependent and reduced by the presence of alternative prey.

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.

Static and dynamic systems in Rickettsia slovaca life cycle evaluated by quantitative real-time polymerase chain reaction.

Quantitative real-time polymerase chain reaction was used to characterize the growth of Rickettsia slovaca, a tick-borne pathogen transmitted by Dermacentor reticulatus and D. marginatus ticks, in static (L929 and Vero cells) and dynamic (D. marginatus and Ixodes ricinus ticks) cultivation systems. The highest points of bacterial multiplication and the time-spans between the inoculum and the maximum of rickettsial copies were increased in consecutive order from eukaryotic cells, I. ricinus to D. marginatus systems. In dynamic system, multiplication maximum of R. slovaca was achieved 9 days earlier in I. ricinus; however, the number of rickettsial DNA copies was approximately 3.6 x 10(6) more in D. marginatus.

Characterization of the immunological response to Dermanyssus gallinae infestation in domestic fowl.

Dermanyssus gallinae is a haematophagous ectoparasite of birds, which adversely affects both production and welfare of commercial poultry. Poultry in commercial production systems chronically exposed to D. gallinae do not appear to develop immunity to the mite. The objective of the current study was to determine the initial immune response of domestic fowl following exposure to D. gallinae. Two groups of birds (11 birds/group) had mite chambers secured to their backs. Controls received no mites, while infested birds received 200 unfed female D. gallinae on day 0 which were then removed on day 1 or 2. Spleen samples were collected on days -1, 1, 2 and 5. The expression of Th1 (IFNgamma, CXCLi2, IL6 and IL18), Th2 (IL4, IL10 and IL13) cytokines/chemokines normalized against a reference gene, GAPDH, were determined by semi-quantitative RT-PCR. Although there were no significant differences between treatments, numerical trends were observed. Th2 cytokine expression was not detected in any birds on any day. IL6, CXCLi2, IFNgamma and IL18 expression was increased on day 1 in the infested group, while on day 2 CXCLi2 and IFNgamma were lower and IL6 and IL18 levels were similar between treatments. The IL18 expression was similar between treatments on day 5, while IL6 and IFNgamma levels were increased and CXCLi2 expression was decreased in the infested group. Data suggest that D. gallinae feeding stimulates Th1 and pro-inflammatory cytokines/chemokines initially (day 1) followed by their subsequent down regulation. This study is the first report of the characterization of the immunological response of the domestic fowl to controlled numbers of D. gallinae.

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.

Effect of plant essential oils as acaricides against the poultry red mite, Dermanyssus gallinae, with special focus on exposure time.

Essential oils from thyme and cade have been shown to be effective acaricides against the poultry red mite, Dermanyssus gallinae (De Geer) when tested over a 24h period. Data on the actual rate of knock-down achieved with these products is lacking and potentially important as essential oils are likely to display only short-term toxicity. When tested over periods of less than 24h, thyme essential oil killed D. gallinae relatively quickly and so may make for an effective acaricide even if the residual toxicity of this product is low. However, cade essential oil did not display such a high level of mite knock-down, suggesting it may hold less promise in D. gallinae management. Comparison of the results with those obtained elsewhere using alternative D. gallinae products further confirms the possibility that thyme essential may be useful in control of this pest. This might be especially true if thyme essential oil were employed as part of an integrated pest management approach.

Comparison of in vivo and in vitro survival and fecundity rates of the poultry red mite, Dermanyssus gallinae.

To assist in the testing of possible antigens in developing a vaccine against the poultry red mite (Dermanyssus gallinae De Geer), a rapid and reliable in vitro screening method is critical. This short paper describes how D. gallinae survival and fecundity rates in an in vivo feeding device compared to that of mites fed using an in vitro method. Results showed that survival of fed D. gallinae females and mites overall was greater in vitro, although there was no difference between male survival and fecundity between in vivo and in vitro designs. The in vitro feeding device described therefore has the potential to provide reliable results, comparable to those obtained by in vivo testing, to allow for the rapid screening of D. gallinae antigens.