The poultry red mite Dermanyssus gallinae (De Geer, 1778): current situation and future prospects for control

In vitro efficacy of ByeMite and Mite-Stop on developmental stages of the red chicken mite Dermanyssus gallinae

The present in vitro study shows the efficacy of two antimite products (ByeMite = phoxim, Mite-Stop = neem seed extract) against all developing stages of the important red chicken mite Dermanyssus gallinae (obtained at two farms in France and Germany). While permanent contact with the active compound led to an efficacy of 100% in the case of Mite-Stop on mites in both farms, there was only a 96.2% killing effect of ByeMite on the mites of the French farm. Even short contacts of only 4 s killed 100% of mites in the case of Mite-Stop at the French farm and only 84.5% in the German farm. ByeMite, on the other hand, killed only 27.8% (Germany) and 30% (France) when mites got the chance to escape from the treated grounds to untreated ones. When using only the half doses of both products, Mite-Stop(R) still reached, after permanent contact, 100% activity on the German farm and 98.2% in France, while ByeMite killed 93.8% (Germany) and 90.6% (France). Short contact to half doses of course reduced the activity of both products (Mite-Stop = 59.3% in France, 22.1% in Germany; ByeMite = 28.8% in France, 18.8% in Germany). With respect to the fumigant activity of the products, the strains of D. gallinae reacted differently. While Mite-Stop(R) showed a clear fumigant activity in the case of the German mites, this product did not affect the French mites by air distribution, neither did ByeMite in both cases. Therefore, mites have to come in contact with both products. Against Mite-Stop, there was apparently no resistance and low doses have high efficacy after even short contacts, which regularly occur in a treated stable, where mites have the chance to leave treated places to untreated hidden spots.

In vitro efficacies of oils, silicas and plant preparations against the poultry red mite Dermanyssus gallinae

The aim of this study was to test the effectiveness of physically acting substances (oils and silicas) and plant preparations for the control of the poultry red mite Dermanyssus gallinae (De Geer 1778). Reproduction and survival of fed D. gallinae females were evaluated in vitro for a total of 168 h using the "area under the survival curve" (AUC) to compare survival of the mites between treatments. Four oils (two plant oils, one petroleum spray oil and diesel), one soap, three silicas (one synthetic amorphous silica, one diatomaceous earth (DE) and one DE with 2% pyrethrum extract) and seven plant preparations (derived from Chrysanthemum cineariaefolium, Allium sativum, Tanacetum vulgare, Yucca schidigera, Quillaja saponaria, Dryopteris filix-mas, and Thuja occidentalis) were tested at various concentrations. All the oils, diesel and soap significantly reduced D. gallinae survival. All silicas tested inhibited reproduction. DE significantly reduced mite survival, but amorphous silica was less effective in vitro. Except for pure A. sativum juice and the highest concentration of C. cineariaefolium extract, the plant preparations tested resulted in statistically insignificant control of D. gallinae.

Exploration of the susceptibility of AChE from the poultry red mite Dermanyssus gallinae (Acari: Mesostigmata) to organophosphates in field isolates from France

The red fowl mite Dermanyssus gallinae (De Geer, 1778) is a hematophagous mite species, which is very commonly found in layer facilities in Europe. The economic and animal health impact of this parasite is quite important. In laying hen houses, organophosphates are almost the only legally usable chemicals. Detecting a target resistance can be useful in order to limit the emergence of resistant populations. The acetylcholinesterase (AChE) activity and the enzyme sensitivity to paraoxon was investigated in 39 field samples and compared to a susceptible reference strain (SSK). Insensitivity factor values (expressed as IC50 ratio) obtained from field isolates compared to SSK revealed some polymorphism but not exceeding a 6-fold difference. The kinetic characteristics of AChE from some field samples showed some difference in KM values for acetylthiocholine and inhibition kinetics performed with diethyl paraoxon exhibited a 5.5-fold difference in the bimolecular rate constant in one field isolate. Taken together, these data suggested that differences in AChE susceptibility to organophosphates may exist in D. gallinae but no resistant population was found.

The testing of antibodies raised against poultry red mite antigens in an in vitro feeding assay; preliminary screen for vaccine candidates

Dermanyssus gallinae (De Geer), the poultry red mite, is a blood-feeding ectoparasite that infests many bird species. We have used an in vitro feeding assay to allow the identification of protective D. gallinae antigens that may have potential as vaccine candidates. Homogenised mites were extracted sequentially with PBS, Tween 20, Triton X100 and urea giving four protein fractions. Five experimental groups of Lohmann Brown hens were used to generate antibodies; four groups were injected with one of each of the protein fractions in QuilA adjuvant and a control group was injected with adjuvant only. Booster injections were administered 2 and 4 weeks after initial immunisation. Eggs were collected throughout the experiment and soluble IgY antibodies were extracted from a pool of egg yolks collected at week six post-injection. Western blots, performed using post vaccination antibodies from test and control groups, revealed a strong antibody response against a range of injected proteins. Fresh chicken blood, supplemented with antibodies raised against these protein fractions, was fed to mites in an in vitro feeding assay in order to determine whether the antibodies had an anti-mite effect. Although there was variability in the numbers of feeding mites, it was found that the strongest anti-mite effect was seen with the PBS protein fraction, which had a cumulative average mortality of 34.8% 14 days after feeding compared with 27.3% for the control group (P = 0.043).

Preventing introduction and spread of Dermanyssus gallinae in poultry facilities using the HACCP method

Preventing the establishment of ectoparasitic poultry red mite (Dermanyssus gallinae) populations is key in ensuring welfare and egg production of laying hens and absence of allergic reactions of workers in poultry facilities. Using the Hazard Analysis and Critical Control Point method, a panel of experts identified hazards and associated risks concerning the introduction and spread of this mite in poultry facilities. Together we provide an overview of possible corrective actions that can be taken to prevent population establishment. Additionally, a checklist of the most critical control points has been devised as management tool for poultry farmers. This list was evaluated by Dutch and British poultry farmers. They found the checklist feasible and useful.

Prevalence and key figures for the poultry red mite Dermanyssus gallinae infections in poultry farm systems

Recent surveys and sample collection have confirmed the endemicity of Dermanyssus gallinae in poultry farming worldwide. The reduction in number and efficacy of many acaricide products has accentuated the prevalence rates of this poultry ectoparasite observed more often in non intensive systems such as free-range, barns or backyards and more often in laying hens than in broiler birds. The lack of knowledge from producers and the utilisation of inadequate, ineffective or illegal chemicals in many countries have been responsible for the increase in infestation rates due to the spread of acaricide resistance. The costs for control methods and treatment are showing the tremendous economic impact of this ectoparasite on poultry meat and egg industries. This paper reviews the prevalence rates of this poultry pest in different countries and for different farming systems and the production parameters which could be linked to this pest proliferation.

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.

Endosymbiotic bacteria living inside the poultry red mite (Dermanyssus gallinae)

This study investigated the endosymbiotic bacteria living inside the poultry red mite collected from five samples of one commercial farm from the UK and 16 farms from France using genus-specific PCR, PCR-TTGE and DNA sequencing. Endosymbiotic bacteria are intracellular obligate organisms that can cause several phenotypic and reproductive anomalies to their host and they are found widespread living inside arthropods. The farm sampled from the UK was positive for bacteria of the genera Cardinium sp. and Spiroplasma sp. From France, 7 farms were positive for Cardinium sp., 1 farm was positive for Spiroplasma sp., 1 farm was positive for Rickettsiella sp. and 2 farms were positive for Schineria sp. However, it was not possible to detect the presence of the genus Wolbachia sp. which has been observed in other ectoparasites. This study is the first report of the presence of endosymbionts living inside the poultry red mite. The results obtained suggest that it may be possible that these bacterial endosymbionts cause biological modifications to the poultry red mite.

Variation in chemical composition and acaricidal activity against Dermanyssus gallinae of four eucalyptus essential oils

The results of this study suggest that certain eucalyptus essential oils may be of use as an alternative to synthetic acaricides in the management of the poultry red mite, Dermanyssus gallinae. At a level of 0.21 mg/cm(2), the essential oil from Eucalyptus citriodora achieved 85% mortality in D. gallinae over a 24 h exposure period in contact toxicity tests. A further two essential oils from different eucalyptus species, namely E. globulus and E. radiata, provided significantly (P < 0.05) lower mite mortality (11 and 19%, respectively). Notable differences were found between the eucalyptus essential oils regarding their chemical compositions. There appeared to be a trend whereby the essential oils that were composed of the fewer chemical components were the least lethal to D. gallinae. It may therefore be the case that the complexity of an essential oil's chemical make up plays an important role in dictating the toxicity of that oil to pests such as D. gallinae.

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.

Monitoring of Dermanyssus gallinae in free-range poultry farms

Various methods for monitoring Dermanyssus gallinae infestations within free-range egg production units were compared. The study was carried out in five egg-producing free-range poultry buildings infested with D. gallinae. Each farm was divided into six zones (each zone including nest boxes, perches and duckboard) for placing two types of traps (corrugated cardboard and thick card traps) or examining dried droppings for presence of mites. Traps were removed 24 h later, placed into bags and mites were counted at the laboratory using binocular magnification. Droppings were also inspected by eye and mite numbers were estimated. All the methods used allowed us to detect mites although their efficacy differed. The number of mites collected was independent of the type of trap used. Examination of the droppings did not differentiate between buildings with differing mite populations. Placing traps in the nest boxes is a less reliable indicator than placing them on the perches. It appears that the most coherent method for evaluating the D. gallinae population within a free-range flock is to place thick card traps throughout the building, on perches favoured by birds.

Comparing therapeutic efficacy between ivermectin, selamectin, and moxidectin in canaries during natural infection with Dermanyssus gallinae

The aim of this study was to compare the efficacy of three spot-on drugs on canaries during Dermanyssus gallinae natural infections and during the breeding season. Three groups of canary couples (seven couples each) were included: group A was treated with ivermectin, B with selamectin, and C with moxidectin. All the drugs were administered topically infrascapularly. The parasitic charge was estimated before the treatment (t(0)) and after 8 (t(1)), 16 (t(2)), 24 (t(3)), and 32 (t(4)) days following the initial treatment. No significant differences were detected among the three tested drugs for the five repeats for each of the four mite stages (egg, larva, nymphs, and fed and unfed adults). With regard to the decrease in the mean numbers of red mites, ivermectin and selamectin exerted their efficacy at t(2), contrary to moxidectin at t(3).

Immunological control of the poultry red mite

In the current study whole poultry red mite antigens were extracted and birds were immunized subcutaneously with either antigen in adjuvant (antigen group) or PBS in adjuvant (control group). Immune responses of birds following immunization were investigated by ELISA and Western blotting, while vaccine efficacy was assessed by feeding of red mites on birds. Immunized birds showed a significant (P < 0.05) increase in IgY titers after immunization compared to controls, while immunoglobulin A (IgA) and IgM did not change significantly. However, the antigen group had a generally higher increase in all immunoglobulin titers compared to the controls. Western blotting identified a number of protein bands at different molecular weights, although these were not different between treatments. PCR analysis of whole mite protein identified bacterial DNA that might have confounded immunological data. In addition, there was a trend toward reduced survival rate of red mites feeding on antigen-immunized birds, but the difference was not statistically significant compared to controls. This study demonstrates the potential for somatic red mite antigens to stimulate an antibody-mediated immune response, although this response did not confer protection to birds.

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.

Laboratory evaluation of three strains of the entomopathogenic fungus Metarhizium anisopliae for controlling Dermanyssus gallinae

The pathogenicity of three strains of the entomopathogenic fungus Metarhizium anisopliae on different life stages of Dermanyssus gallinae was evaluated in the laboratory. All the strains tested were virulent to D. gallinae but pathogenicity varied among the strains. Strain V245 induced a higher mortality rate using different concentrations than other two strains. The estimated median lethal concentration of different strains of M. anisopliae against D. gallinae varied depending on the exposure time of D. gallinae to M. anisopliae. It was concluded that the pathogenicity of the entomopathogenic fungus M. anisopliae on different life stages of D. gallinae was concentration and time dependent.

Histamine release factor from Dermanyssus gallinae (De Geer): characterization and in vitro assessment as a protective antigen

A cDNA encoding a 174-amino-acid orthologue of a tick histamine release factor (HRF) was identified from the haematophagous poultry red mite Dermanyssus gallinae. The predicted D. gallinae HRF protein (Dg-HRF-1) sequence is highly conserved with the tick HRFs (identity 52-54%) and to a lesser degree with translationally controlled tumour proteins (TCTP) from mammals and other invertebrates (range 38-47%). Phylogenetically, Dg-HRF-1 partitions with the tick HRF clade suggesting a shared linage and potentially similar function(s). A recombinant Dg-HRF-1 protein (rDg-HRF-1) was produced and shown to induce degranulation of rat peritoneal mast cells in vitro, confirming conservation of the histamine-releasing function in D. gallinae. Polyclonal antibodies were generated in rabbits and hens to rDg-HRF-1. Western blotting demonstrated that native Dg-HRF is a soluble protein and immunohistochemical staining of mite sections revealed that the distribution of Dg-HRF, although ubiquitous, is more common in mite reproductive, digestive and synganglion tissues. A survey of hens housed continuously in a mite-infested commercial poultry unit failed to identify IgY specific for recombinant or native Dg-HRF, indicating that Dg-HRF is not exposed to the host during infestation/feeding and may therefore have potential as a vaccine using the concealed antigen approach. To test the protective capability of rDg-HRF-1, fresh heparinised chicken blood was enriched with yolk-derived anti-Dg-HRF IgY antibodies and fed to semi-starved mites using an in vitro feeding system. A statistically significant increase in mortality was shown (P=0.004) in mites fed with anti-Dg-HRF IgY after just one blood meal. The work presented here demonstrates, to our knowledge for the first time, the feasibility of vaccinating hens with recombinant D. gallinae antigens to control mite infestation and the potential of rDg-HRF-1 as a vaccine antigen.

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.

Genetic differences in internal transcribed spacer 1 between Dermanyssus gallinae from wild birds and domestic chickens

We investigated the presence of the poultry red mite or the chicken mite, Dermanyssus gallinae De Geer, Acari: Dermanyssidae, in wild bird populations in four different geographical regions of Sweden. The mites identified as D. gallinae were compared genetically with D. gallinae from egg-producing poultry farms in the same regions. The small subunit (SSU) gene, the 5.8S ribosomal RNA (rRNA) gene and the two internal transcribed spacers (ITS) of the rRNA genes were used in the genetic analysis. All D. gallinae mites had identical SSU rRNA, 5.8S rRNA and ITS2 sequences independent of their origin. By contrast, we identified significant differences in the ITS1 sequences. Based on the differences in the ITS1 sequences, the mites could be divided into two genotypes, of wild and domesticated origin, with no variation within the groups. These results imply that wild bird populations are of low importance, if any, as natural reservoirs of D. gallinae in these four geographical regions of Sweden.

Colonization and organ invasion in chicks experimentally infected with Dermanyssus gallinae contaminated by Salmonella Enteritidis

The poultry red mite (Dermanyssus gallinae) is the most important and common ectoparasite of laying hens in Europe. This haematophagous mite has been experimentally demonstrated to be a vector of Salmonella Enteritidis by acquiring bacteria through the blood meal or cuticular contact. We have evaluated another route of infection by orally inoculating chicks with mites previously infected by S. Enteritidis. Two methods of infecting the mites were tested: mites contaminated by cuticular contact or during the blood meal. After the washing of mites with paraformaldehyde, groups of 10 Salmonella-contaminated mites were inoculated individually into 1-day-old chicks. The titre of the inoculum suspension was evaluated by crushing mites and followed by bacteriological counting. It was 3x10(4) colony-forming units/chick and 2.7x10(6) colony-forming units/chick, respectively, for cuticular contact and orally mediated contamination of mites. Each bird was found to be positive 12 days post-inoculation. Salmonella colonized the intestinal tracts and invaded the livers and spleens. The caecal content concentration reached a mean level of S. Enteritidis of 8.5x10(4) most probable number (MPN) Salmonella/g. This experiment demonstrated the ability of mites to orally infect 1-day-old chicks with subsequent colonization and multiplication of Salmonella. Consequently, mites infected by S. Enteritidis constitute potential reservoir hosts of this bacterium, allowing it to persist in the poultry house as a source of infection for newly introduced animals. If contaminated mites are found in poultry facilities, effective red mite control should be performed before new batches are introduced into the facility.

Penetration studies of propoxur and phoxim from eggshell into whole egg after experimental exposure and application in henhouses

The penetration of propoxur and phoxim from eggshell into whole egg was investigated in vitro by spraying eggs directly and in vivo after application of the compounds in henhouses. Although mean concentrations of the compounds on eggshells were up to 23000 microg kg(-1), mean residue concentrations in whole eggs were far below the current maximum residue levels (50 microg kg(-1) for propoxur and 60 microg kg(-1) for phoxim). These results provide the first evidence that propoxur and phoxim do not penetrate from eggshell into whole egg under experimental and field conditions. Subsequently, residue carry-over after egg cracking in households and during a worst-case situation in an egg-cracking plant was investigated. However, when eggs were cracked manually, a negligible contamination of whole egg values occurred. If, in an automated process, eggshells accidentally come into close contact with whole egg, very high residue levels of propoxur and phoxim may be generated time dependently. These results suggest that eggshell contact with whole egg during egg cracking must be avoided to prevent pesticide carry-over.

Field efficacy of phoxim 50% (ByeMite®) against the poultry red mite Dermanyssus gallinae in battery cages stocked with laying hens

Infestations with the poultry red mite Dermanyssus gallinae represent a major ectoparasite problem in poultry and can affect egg layers worldwide. There is presently a lack of an ectoparasiticide in Europe for poultry which can assure a 0-day withholding period for eggs. In this study, ByeMite (phoxim 50%, Bayer HealthCare, Animal Health Division) was administered to treat a D. gallinae infestation in a poultry house stocked with egg-laying hens kept in a cage system. A layer house was sprayed twice within a 7-day interval using a solution containing 2000 ppm phoxim and a similar layer house was used as an untreated control unit. Specially developed D. gallinae traps made of cardboard were used to assess the mite density in both layer houses during a 49-day period after the treatment. In order to collect mites, the traps were placed on days--1, 2, 6, 9, 13, 20, 34 and 48 and always removed after 24 h. The collected mites were counted and differentiated according to their developmental stage (mite eggs, larvae, nymphs, adults). Three days after the first spray treatment, the efficacy against all mite stages (larvae, nymphs, adults) was 96.1%, and from day 7 post-treatment until the end of the trial (day 49) the efficacy exceeded 99%. In contrast, in the untreated layer house (negative control group) the mite population showed a 400% increase. No treatment-related side effects in chickens were detectable. It is concluded that two administrations of ByeMite within a 7-day interval are highly effective against D. gallinae infestations in a stocked poultry house.

Determination of phoxim residues in eggs by using high-performance liquid chromatography diode array detection after treatment of stocked housing facilities for the poultry red mite (Dermanyssus gallinae)

The poultry red mite Dermanyssus gallinae is the most important ectoparasite of poultry in several European countries. Phoxim is a well-known antiparasitic agent in wide use. Initial studies indicated that this compound could successfully be applied to eliminate D. gallinae in egg-laying birds and in henhouses by treating the cages and the equipment with it. In order to investigate whether phoxim residues are present in eggs from laying hens, we developed a selective and sensitive high-performance liquid chromatography method employing a simple water/acetonitrile gradient system. The amount of phoxim was determined by UV detection at 281 nm, and the presence of the residue was confirmed by diode array detection. The eggs were homogenized for sample pretreatment and extracted with acetonitrile and partitioned with n-hexane. The acetonitrile extract was further purified with silica gel column chromatography. Recovery rates (performed at the 5-120 microg kg(-1) level) were in the range of 86.0-92.1% with relative standard deviations between 3.1% and 16.3%. Based on a signal to noise ratio of 3, the limit of detection of the assay was approximately 2 microg kg(-1). The day-to-day variation in the concentration of phoxim in four contaminated eggs (5.7-51.6 microg kg(-1)) was generally less than 20%. The decision limit (CCalpha) and the detection capability (CCbeta) were 62.0 and 68.7 microg kg(-1), respectively. The applicability of the method was demonstrated in eggs from three clinical trials and from a field study. In these investigations, all animals were kept in conventional battery cages. No sample was found containing more than the maximum residue level of 60 microg kg(-1) for phoxim in eggs as given in Annex I of Council Regulation (EEC) No. 2377/90.

Contact and fumigant toxicity of oriental medicinal plant extracts against Dermanyssus gallinae (Acari: Dermanyssidae)

The acaricidal activity of methanolic extracts from 40 oriental medicinal plant species and a steam distillate of Cinnamomum camphora towards poultry house-collected adult Dermanyssus gallinae De Geer was examined using direct contact and vapour phase toxicity bioassays. Results were compared with those of 15 acaricides currently used. In filter paper contact toxicity bioassays using adult D. gallinae, C. camphora steam distillate (0.0051 mgcm(-2)) was the most toxic material, followed by extracts from Asarum sieboldii var. seoulens whole plant, Eugenia caryophyllata flower bud and Mentha arvensis var. piperascens whole plant (0.0063-0.0072 mgcm(-2)), based upon 24h LD(50) values. The acaricidal activity of these four plant preparations was almost comparable to that of profenofos (LD(50), 0.003 mgcm(-2)) but less effective than dichlorvos (LD(50), 0.0004 mgcm(-2)). The toxicity of Illicium verum fruit and Lysimachia davurica leaf extracts (0.09 mgcm(-2)) was almost comparable to that of benfuracarb, prothiofos, propoxur and fenthion (0.053-0.070mgcm(-2)). In vapour phase toxicity tests, these plant preparations were more effective in closed containers than in open ones, indicating that the mode of delivery of these plant extracts was largely a result of action in the vapour phase. Plants described herein merit further study as potential D. gallinae control agents.

Assessment of susceptibility of the poultry red mite Dermanyssus gallinae (Acari: Dermanyssidae) to some acaricides using an adapted filter paper based bioassay

A previously described bioassay was modified to assess the response of the poultry red mite, an important ectoparasite of fowl, to a selected group of acaricides. The adapted bioassay is simple to use, escape-proof and provides data that can be subjected to probit analysis. The reproducibility of the method was assessed by three tests with alpha-cypermethrin against a reference strain, which produced dose-response lines that did not differ significantly (chi(2)=1.39, 2 d.f., p=0.50), and had a derived common slope of 1.89. In addition, a limited evaluation study enabled assessment of response to commercial formulations of bifenthrin, bifenthrin+malathion and cypermethrin by field populations of the poultry red mite.

Ability of a proteinase inhibitor mixture to kill poultry red mite, Dermanyssus gallinae in an in vitro feeding system

The development of a reliable in vitro feeding system has enabled the rapid testing of presumptive anti-mite factors, a mixture of protease inhibitors (PI), by incorporating these into the blood feed. Mites were collected from a caged-hen facility and underwent a regime of starvation under varying conditions of temperature and darkness to determine the optimum conditions that encouraged mites to feed in the in vitro system. The efficacy of two anti-coagulants, heparin (HS) and acid citrate glucose (ACD), on mite feeding rates and mortality was evaluated. The ability of a mixture of PI to kill mites was also evaluated. The rate of feeding was greater in mites that were starved and cooled for between 7 and 30 days compared with mites that were not starved or cooled. The percentage of mites that fed when presented with HS treated blood (70%) was greater when compared with ACD treated blood (48%). The mortality of mites fed blood treated with HS + PI increased to 45% compared with a mortality level of 5% in mites fed on blood treated with HS alone. A reliable in vitro method for feeding D. gallinae which has the potential to be used to rapidly screen blood-borne products for their efficacy in reducing mite numbers has been developed.

A house dust mite allergen homologue from poultry red mite Dermanyssus gallinae (De Geer)*

Tropomyosin is an allergenic, actin-binding protein and a proposed vaccine candidate from several species of parasite. Tropomyosin cDNA, obtained by polymerase chain reaction (PCR) amplification from Dermanyssus gallinae RNA, encoded a predicted protein with 89% and 88% identity to tropomyosins from the ticks Boophilus microplus and Haemaphysalis longicornis, respectively, and 85% identity to the house dust mite (HDM) tropomyosin Der p 10. Mouse antibodies raised against HDM tropomyosin reacted with a band of 38 kDa on Western blots of D. gallinae extract, consistent with the molecular masses of acarine tropomyosins and the putative product of the cDNA encoding D. gallinae tropomyosin. When the same preparation of D. gallinae proteins was used in Western blots with serum from infested hens, the IgY component of the serum bound to a number of mite proteins, but not to tropomyosin, indicating that hens are not directly exposed to this allergen during a natural infestation. Immunolocalization of tropomyosin in mites indicated a ubiquitous distribution of the molecule in mite tissues. Immunolocalization and Western blotting also indicated that poultry red mites ingest host IgY.

Azadirachtin-impregnated traps for the control of Dermanyssus gallinae

The effect of neem oil (azadirachtin), originating from the tree Azadirachta indica, was investigated as a potential compound to control the poultry red mite, Dermanyssus gallinae. In vitro tests were performed to determine the most appropriate formulation of neem extracts and concentration of the substance to be used. Cardboard traps containing 20% neem oil were placed at the mites' aggregation sites, out of reach of the hens, in a floor system for layers containing approximately 2400 birds. Treated traps were replaced every week for 4 weeks. Throughout the study, the parasite population was monitored by collections of mites with untreated plastic traps. A 92% reduction of D. gallinae was recorded.

Effect of food deprivation on response of the mite, Dermanyssus gallinae, to heat

Freshly blood-fed adult females of the chicken mite Dermanyssus gallinae DeGeer (Acari: Dermanysidae) were food-deprived during 1, 2-3, 8-10, 14-16 and 22-23 days. These mites were tested in groups of 10 to determine their sensitivity to a heat cue delivered for a 60 s period under controlled laboratory conditions (24 degrees C, simulated dark conditions of 2 lx). Immobile mites were videotaped and start of activation (for individual mites) and percentage of mites activated in the 60 s period were related to temperature changes. Mites were activated with temperature gradients as low as 0.003-0.005 degrees C/s. Mites that had fed the previous day had a significantly lower activation (20%) than other groups. Activation was highest at 2-3 days (60%) and 8-10 days (75%) post-feeding. Activation declined significantly to 45% at 14-16 days and to 30% at 22-23 days post-feeding. Activation patterns probably reflect mite physiological condition and declining responsiveness to heat cues concomitant with starvation and higher risks associated with activation in the prolonged absence of a host.

Acaricide Resistance in Northern Fowl Mite (Ornithonyssus sylviarum) Populations on Caged Layer Operations in Southern California

Southern California caged layer operations were visited over 3 yr. Northern fowl mites from 26 field populations were tested for acaricide resistance using a capillary pipette and glass dish bioassay. One was a susceptible field population with no pesticide exposure for over 30 yr (reference site for resistance ratio calculation). Technical and commercial formulations of malathion, carbaryl (Sevin), permethrin, and a commercial formulation of tetrachlorvinphos/dichlorvos (Ravap) were tested. Malathion did not have high activity for mites relative to other materials, but resistance to both technical and commercial formulations was low (< 5x). Resistance to other materials was moderate to extreme. Frequency of carbaryl resistance (> 10x) was higher with the commercial (88%) than the technical material (41%); 19% of the populations had resistance > 100x to commercial carbaryl. Frequency of Ravap resistance (> 10x) was 68%; 8% of populations had resistance > 100x. Frequency of permethrin resistance (> 10x) was 72% for the technical material and 88% for the commercial formulation. Extreme permethrin resistance (> 1,000x) was observed in 56 and 50% of mite populations assayed using the technical and commercial formulations, respectively. Among sites, resistance to permethrin was uncorrelated with resistance to other chemicals, suggesting a different resistance mechanism. Resistance to carbaryl and Ravap was highly correlated [r = 0.76 at the LC50 level (concentrations estimated to be lethal to 50% of the test population) and r = 0.99 at the LC95 level], suggesting a common resistance mechanism. Producers currently depend completely on pesticides to control mite infestations. Mite resistance to registered materials emphasizes the need for integrated control measures.

Traps containing acaricides for the control of Dermanyssus gallinae

In Sweden, the poultry red mite, Dermanyssus gallinae, is the only haematophagous mite of poultry. After obtaining a blood meal the parasite spends most of its life off the host aggregated in cracks and crevices where mating and reproduction occur. Cardboard traps (1000 mm x 40 mm x 3 mm; 160 mm x 140 mm x 3 mm and 100 mm x 70 mm x 3 mm) containing 2% metriphonate were placed where mites gathered, out of reach of the hens, in two different types of multi-tiered floor systems for layers. In two separate trials, treated traps were replaced every second day for 2 weeks and every week for 8 weeks. In the 2-week trial the whole floor system was treated while in the 8-week trial six of 12 existing compartments studied were treated. The untreated compartments were used as controls. Throughout the study, the parasite populations were monitored by collections of mites with untreated cardboard traps (100 mm x 70 mm x 3 mm). A 95% reduction of mites was recorded in the 8-week trial whereas a 99% reduction of mites was recorded in the 2-week trial. The placement of treated traps near mite aggregation sites was essential for satisfactory control.

Effect of permethrin impregnated plastic strips on Dermanyssus gallinae in loose-housing systems for laying hens

The effect of permethrin impregnated plastic strips (Die No Mite Strips) was evaluated on Dermanyssus gallinae populations in aviary systems for layers in Sweden. Two application strategies of the strips were tested: (A) attached in the housing system, allowing the birds to rub against the strips and thereby get the acaricide released onto their plumage, and (B) attached out of reach of the hens, at two different sites (perches and egg-belt lids) of the inner surfaces of the system, where the mites sheltered during the day. On two farms with 2030 (A) and 3384 (B) hens, and existing mite populations, strips were mounted for 20 and 10 weeks, respectively, and mite numbers were monitored by traps. With application A an overall mite reduction of 53% was observed, while with B the mean mite numbers decreased by 39% at the perches and 92% at the egg-belt lid. The strips were originally designed for caged hens afflicted by ectoparasites that stay on the host for most of their life cycle. However, since D. gallinae spends most of its time off the host, it was not possible to control the parasite with application A. Resistance tests performed on mites from both treated and control compartments where application A was used showed no indication of resistance to permethrin, while 95% of the mites survived a 48 h exposure to the compound where application B was performed. Thus, permethrin resistant mites appeared to be the main reason for the failure to control D. gallinae with application B.