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.

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.

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.

The role of nutrients in the prevention and treatment of Alzheimer's disease: methodology for a systematic review.

There is a large body of existing data on nutrition in Alzheimer's disease (AD). We are conducting a systematic review of published scientific literature to determine the role of specific nutrients, both individually and in combination, in the prevention and treatment of AD. This will contribute towards a structured evidence base to help inform the clinical management of AD. The objective of the systematic review is to evaluate the strength of evidence from both observational cohort studies and randomized controlled trials on the role of fats, vitamins, antioxidants and other nutrients in the prevention and treatment of AD. We present here the methodology of our systematic review.

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.

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.

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.

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.

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.

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.

In vitro and in vivo acaricidal activity and residual toxicity of spinosad to the poultry red mite, Dermanyssus gallinae.

This paper describes two experiments conducted to examine the acaricidal potential of spinosad against the poultry red mite, Dermanyssus gallinae (De Geer), a serious ectoparasitic pest of laying hens. Spinosad is a natural product derived from the fermentation of the micro-organism Saccharopolyspora spinosa. In vitro testing confirmed that, when applied to a galvanised metal plate to the point of run-off, spinosad was toxic to adult female D. gallinae and suggested that at an application rate of 3.88 g/L a significant residual toxicity of spinosad could be achieved for up to 21 days. A subsequent in vivo experiment in a conventional cage housing system for laying hens demonstrated the acaricidal activity and residual toxicity to D. gallinae of a single application of spinosad when applied at either 1.94 or 3.88 g/L. Residual toxicity of spinosad at both of these application rates was maintained throughout the course of the 28 day post-spray study period, with a peak in product efficacy seen 14 days after spraying. The results suggest that the greater the D. gallinae population the greater will be the toxic effect of spinosad. Although the exact reasons for this are unclear, it can be speculated that conspecifics spread the product between each other more efficiently at higher mite population densities. However, further study is warranted to confirm this possibility. Application of spinosad in vivo had no effect on hen bodyweight or egg production parameters (number and weight), suggesting that this product could be used to effectively control D. gallinae infestations whilst birds are in lay. This paper also describes a novel method for effectively and efficiently achieving replication of treatments in a single poultry house, previously unpopulated with D. gallinae. Individual groups of conventional cages were stocked with hens, seeded with D. gallinae and used as replicates. Independence of replicates was achieved by isolating cage groups from one another using a non-drying glue barrier to minimise D. gallinae migration. Creating isolated populations (replicates) of D. gallinae within a single poultry house thus represents a novel and efficient means of screening other potential acaricides under field conditions.

The effects of the stress caused by experimental procedures on alanine, aspartate, glutamate and glutamine in rat liver.

Rats were stressed by intravenous injection, tail-warming or moderate restraint for 30s, i.e. by stresses imposed by normal handling during experiment. Liver glutamate concentrations were greatly affected. The results were substantially the same in two varieties of rat (Wistar and Sprague-Dawley), in two laboratories, in experiments carried out by two sets of workers, and after all three stresses. The following detailed results refer to Wistar rats. 1. In starved rats at 20 degrees C and 30 degrees C and in post-absorptive rats at 20 degrees C stress by injection raised liver glutamate concentrations from 1.54, 1.57 and 1.88mumol/g wet wt. 30s after injection to 3.4, 2.7 and 3.6mumol/g wet wt. respectively a few minutes later. In starved rats at 20 degrees C the concentration then fell slowly to 2.3mumol/g wet wt., in starved rats at 30 degrees C it remained steady, and in post-absorptive rats at 20 degrees C it rose slowly to about 4.3mumol/g wet wt. The final values seemed fairly steady and corresponded to an ;alert' state. 2. In starved rats at 20 degrees C anaesthesia, with or without injection or cannulation during it, raised glutamate concentrations to the ;alert' values, which were maintained for 2-3h. 3. Liver alanine concentration in post-absorptive rats initially fell from 1.5 to 0.8mumol/g, and then stayed fairly constant. 4. Aspartate and glutamine concentrations altered only in starved rats, and proportionately much less than those of glutamate. 5. The necessity for knowing the time-dependence of glutamate concentrations after experimental handling is emphasized. 6. There is no wholly satisfactory explanation of the observations.