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PubMed1992

Epidemiology of dust-mite-related disease.

For many years it has been suggested that allergens derived from the house dust mite played a major role in the pathogenesis of asthma, eczema and some cases of allergic rhinitis. Recently, house dust mite allergens have been purified and specific immunoassays developed with which exposure to house dust mites and their allergens can be more easily determined. Using these tools, epidemiological studies have provided confirmatory evidence that not only is house dust mite exposure associated with the majority of cases of asthma in children and young adults, but that it is causally related to the development of asthma.

Adult↗
PubMed1994

Examination of possible transmission of sheep scab mite Psoroptes ovis between host species.

Examination of possible transmission of the Irish strain of the sheep scab mite (Psoroptes ovis) of ovine origin between host species involved calves and goats being placed with infected sheep and also directly challenged with live mites. Although mites remained on recipient species for up to a week, they failed to produce disease in either of these species. Calves and goats that had live mites placed on them likewise failed to infect sheep with which they were housed.

Animals↗
PubMed2003

Ultrastructure and bacterial infection of wounds in honey bee ( Apis mellifera) pupae punctured by Varroa mites.

The damage to western honey bee, Apis mellifera, colonies caused by the originally Asian ectoparasitic mite Varroa destructor is mainly a consequence of the infestation of host bee pupae. In the capped brood cell, female mites puncture the host's integument at preferred sites in order to suck haemolymph. Due to repeated feeding by the mother mite and her progeny, these perforations are kept open until shortly before the imaginal moult of the bee. Thereafter scarring takes place, thus preventing microbial infection after the adult bee has emerged from the protected environment of the sealed brood cell. However, colonies of various bacteria were found in the open wounds of about 15-30% of all inspected host pupae with an abundance depended on the level of host brood cell infestation by the mite. The small punctures of the pupal integument are difficult to detect but, by vital staining with trypan blue, the wounds can be visualised. The ultrastructure of the pupal wounds, the bacterial colonies and the scarring process are documented by a series of scanning electron micrographs.

Animals↗
PubMed2006

Population dynamics of thrips prey and their mite predators in a refuge.

Prey refuges are expected to affect population dynamics, but direct experimental tests of this hypothesis are scarce. Larvae of western flower thrips Frankliniella occidentalis use the web produced by spider mites as a refuge from predation by the predatory mite Neoseiulus cucumeris. Thrips incur a cost of using the refuge through reduced food quality within the web due to spider mite herbivory, resulting in a reduction of thrips developmental rate. These individual costs and benefits of refuge use were incorporated in a stage-structured predator-prey model developed for this system. The model predicted higher thrips numbers in presence than in absence of the refuge during the initial phase. A greenhouse experiment was carried out to test this prediction: the dynamics of thrips and their predators was followed on plants damaged by spider mites, either with or without web. Thrips densities in presence of predators were higher on plants with web than on unwebbed plants after 3 weeks. Experimental data fitted model predictions, indicating that individual-level measurements of refuge costs and benefits can be extrapolated to the level of interacting populations. Model-derived calculations of thrips population growth rate enable the estimation of the minimum predator density at which thrips benefit from using the web as a refuge. The model also predicted a minor effect of the refuge on the prey density at equilibrium, indicating that the effect of refuges on population dynamics hinges on the temporal scale considered.

Animals↗
PubMed2004

Predation risk affects diapause induction in the spider mite Tetranychus urticae.

Whenever diapause induction triggers movement into another microhabitat or the development of protective morphological structures, this may also alter predation risk. If the risk of being eaten is lower in the diapause phase, then there may be selection favouring diapause induction in response to predators or their cues. In this article, we studied the effect of the predatory mite Typhlodromus pyri on diapause induction in the spider mite Tetranychus urticae. We used a Greek strain because under long-night photoperiods and low temperature only part of the population enters diapause, thereby leaving room for the impact of another factor. In spider mite groups under predation, the percentage diapause induction increased whenever night-lengths were such that diapause was induced (13-16 h of night). Given this diapause induction in response to predation risk, the question arises whether entering diapause helps spider mites to escape from predation and contribute more offspring to the spring generation next year.

Adaptation, Physiological↗
PubMed2005

Observations on the honey bee tracheal mite Acarapis woodi (Acari: Tarsonemidae) using low-temperature scanning electron microscopy.

Observations were made of cryo-preserved honey bee tracheal mites Acarapis woodi (Rennie) using scanning electron microscopy. We describe various new morphological attributes of A. woodi based on the ability of the cryo-technique to capture live mites in natural positions and observe the Low-Temperature Scanning Electron Microscopy (LT-SEM) photographs under a 3-D viewer. Most striking was the observation that each leg has the ability to independently twist its segments with the ambulacrum rotating a minimum of 180 degrees during locomotion; this is a more sophisticated form of locomotion than has been proposed for the Acari. Adult daughter mites are known to be the dispersal instar moving from the tracheal tube to the thoracic hairs of the bee and then transferring to a new bee. We hypothesize that adult tarsal claws and setae on the legs play a role in attachment to hairs during dispersal. However, our evidence is that none of the life stases use their tarsal claws within the tracheal tubes. Larvae were observed to be 'freely moving' within the tracheal system, their tarsal claws rendered inoperative due to an enlarged swollen pulvillar pad. The solenidia of leg I are now known to have striations and the famulus is bifurcated. The bifurcated famulus, solenidial striations, and segmentation of leg IV of females may have taxonomic implications in the family Tarsonemidae. The body and leg setae of adults appear to be used as a tactile tool to sense the amount of space within the tracheal tubes; most of the setae are oriented distally and may help the mite to measure the space or radius of the tracheal tubes. The modified caudal region of the male revealed remnants of the h1 and h2 setae and a smooth clean surface, void of a film, supporting that pharate nymphs are not attached in this species.

Animals↗
PubMed2005

In vitro and in vivo inhibition of alpha-amylases of stored-product mite Acarus siro.

The stored-product mites are the most abundant and frequent group of pests living on the stored food products in Europe. They endanger public health since they produce allergens and transmit mycotoxin-producing fungi. Novel acaricidal compounds with inhibitory effects on the digestive enzymes of arthropods are a safe alternative to the traditional neurotoxic pesticides used for control of the stored-product pests. In this work, we explored the properties of acarbose, the low molecular weight inhibitor of alpha-amylases (AI), as a novel acaricide candidate for protection of the stored products from infestation by Acarus siro (Acari: Acaridae). In vitro analysis revealed that AI blocked efficiently the enzymatic activity of digestive amylases of A. siro, and decreased the physiological capacity of mite's gut in utilizing a starch component of grain flour. In vivo experiments showed that AI suppressed the population growth of A. siro. The mites were kept for three weeks on experimental diet enriched by AI in concentration range of 0.005 to 0.25%. Population growth of A. siro was negatively correlated with the content of AI in the treated diet with a half-population dose of 0.125%. The suppressive effect of AIs on stored-product mites is discussed in the context of their potential application in GMO crops.

Acarbose↗
PubMed2005

Predation by Allothrombium pulvinum on the spider mites Tetranychus urticae and Amphitetranychus viennensis: predation rate, prey preference and functional response.

The deutonymphs of Allothrombium pulvinum Ewing (Acari: Trombidiidae) are among the most important natural enemies of spider mites in North, North East and West Iran. In this study, maximum predation rate and preference experiments were conducted with A. pulvinum deutonymphs on apple leaf discs, to determine their preference for either of two spider mite species: Amphitetranychus viennensis (Zacher) and Tetranychus urticae Koch (Acari: Tetranychidae). Maximum predation rate tests showed that the predatory mite consumed more eggs and females of T. urticae than of A. viennensis. Furthermore, the Manly's preference index for eggs and females of T. urticae confirmed that T. urticae were the preferred prey. The functional response of A. pulvinum deutonymphs on females of T. urticae was examined over a 24-h period. Predation of A. pulvinum deutonymphs presented with females of T. urticae followed a type III functional response. Estimated handling time for the predatory mites was 4.51 h and attack coefficient b, which describes the changes in attack rate with prey densities in a type III functional response, was 0.021.

Animals↗
PubMed2006

Does methyl salicylate, a component of herbivore-induced plant odour, promote sporulation of the mite-pathogenic fungus Neozygites tanajoae?

Blends of volatile chemicals emanating from cassava leaves infested by the cassava green mite were found to promote conidiation of Neozygites tanajoae, an entomopathogenic fungus specific to this mite. Methyl salicylate (MeSA) is one compound frequently present in blends of herbivore-induced plant volatiles (HIPV) as well as that of mite-infested cassava. Here, we investigated the effect of methyl salicylate in its pure form on the production of pre-infective spores (conidia), and the germination of these spores into infective spores (capilliconidia), by a Brazilian isolate and a Beninese isolate of N. tanajoae. Mummified mites previously infected by the fungal isolates were screened under optimal abiotic conditions for sporulation inside tightly closed boxes with or without methyl salicylate diffusing from a capillary tube. Production of conidia was consistently higher (37%) when the Beninese isolate was exposed to MeSA than when not exposed to it (305.5 +/- 52.62 and 223.2 +/- 38.13 conidia per mummy with and without MeSA, respectively). MeSA, however, did not promote conidia production by the Brazilian isolate (387.4 +/- 44.74 and 415.8 +/- 57.95 conidia per mummy with and without MeSA, respectively). Germination of the conidia into capilliconidia was not affected by MeSA for either isolate (0.2%, 252.6 +/- 31.80 vs. 253.0 +/- 36.65 for the Beninese isolate and 4.2%, 268.5 +/- 37.90 vs. 280.2 +/- 29.43 for the Brazilian isolate). The effects of MeSA on the production of conidia were similar to those obtained under exposure to the complete blends of HIPV for the case of the Beninese isolate, but dissimilar (no promoting effect of MeSA) for the case of the Brazilian isolate. This shows that MeSA, being one compound out of many HIPV, can be a factor promoting sporulation of N. tanajoae, but it may not be the only factor as its effect varies with the fungal isolate under study.

Animals↗
PubMed2006

The predatory mite Phytoseiulus persimilis adjusts patch-leaving to own and progeny prey needs.

Integration of optimal foraging and optimal oviposition theories suggests that predator females should adjust patch leaving to own and progeny prey needs to maximize current and future reproductive success. We tested this hypothesis in the predatory mite Phytoseiulus persimilis and its patchily distributed prey, the two-spotted spider mite Tetranychus urticae. In three separate experiments we assessed (1) the minimum number of prey needed to complete juvenile development, (2) the minimum number of prey needed to produce an egg, and (3) the ratio between eggs laid and spider mites left when a gravid P. persimilis female leaves a patch. Experiments (1) and (2) were the pre-requirements to assess the fitness costs associated with staying or leaving a prey patch. Immature P. persimilis needed at least 7 and on average 14+/-3.6 (SD) T. urticae eggs to reach adulthood. Gravid females needed at least 5 and on average 8.5+/-3.1 (SD) T. urticae eggs to produce an egg. Most females left the initial patch before spider mite extinction, leaving prey for progeny to develop to adulthood. Females placed in a low density patch left 5.6+/-6.1 (SD) eggs per egg laid, whereas those placed in a high density patch left 15.8+/-13.7 (SD) eggs per egg laid. The three experiments in concert suggest that gravid P. persimilis females are able to balance the trade off between optimal foraging and optimal oviposition and adjust patch-leaving to own and progeny prey needs.

Animals↗
PubMed2006

Microenvironmental preferences of oribatid mite species on the floor of a tropical rainforest.

The vertical distribution, microenvironmental preference, canopy cover, as well as monthly fluctuations of recently described species of three genera of macropyline oribatid mites, Mesoplophora, Bicyrthermannia and Nothrus and three genera of brachypyline mites, Scheloribates, Muliercula and Galumnella were investigated over a 9-month period in shaded and unshaded areas of a secondary regrowth forest floor in Ile Ife, Nigeria. Sampling was done monthly from August 2002 to April 2003 covering the two seasons of the annual cycle. There was an overwhelming predominance of mite populations in the 5 cm topsoil compared with the fermentation and litter layers. The preference of M. ifeana and B. nigeriana extracted from the topsoil for the shaded plot was attributed to highly conducive moisture conditions provided by the canopy. It is suggested that M. ifeana, B. nigeriana, N. lasebikani, S. mochlosimilaris, M. inexpectata and G. sonpona, that exhibited a single peak density in the wet season in this study, had similar ecological needs. The populations of M. ifeana and S. mochlosimilaris were relatively stable in the fermentation layer. The study concluded that canopy cover affected the sensitivity of soil dwelling mites on the floor of a secondary regrowth forest with regard to vertical gradients of light, microclimate and foliage quality in a complex way.

Animals↗
PubMed2005

Components of honeybee royal jelly as deterrents of the parasitic Varroa mite, Varroa destructor.

The parasitic mite Varroa destructor Anderson & Trueman reproduces on the immature stage of the honeybee, Apis mellifera L. Mites are found more often on drone brood than worker brood and only infrequently on queen brood. We investigated the chemical basis for the low incidence of mites on queen brood. V. destructor mites were deterred by a crude extract of royal jelly, a glandular secretion produced by nurse bees and fed to queen larvae. Bioassay-driven fractionation of the crude extract via column chromatography resulted in one active fraction that was as active as the crude extract. Compounds in the active fraction were identified using gas chromatography (GC) and coupled gas chromatography/mass spectrometry (GC-MS). Before injection, compounds were esterified with MeOH/sulfuric acid, followed by silylation of any hydroxyl groups present. The active fraction contained at least 22 compounds, all fatty acids, several of which contained an additional hydroxyl group on the alkyl chain. Synthesis of some of these compounds that are not commercially available is described. A synthetic mixture containing most of the compounds in the active fraction was as active as the active fraction in the bioassay.

Animals↗
PubMed1978

House dust mite hyposensitization.

A double-blind controlled trial of house dust mite hyposensitization was carried out in 14 patients with asthma, who were hypersensitive on skin testing to the house dust mite alone. Measurements were made, using a Wright's peak flowmeter, during the 15-month trial period. Precautions were taken in the home to reduce the mite population. At the end of the trial, no clinical improvement was noted subjectively or objectively, despite a reduced bronchial sensitivity to allergen in the treated group. The role of the house dust mite as a cause of asthma is discussed.

Adolescent↗
PubMed1984

Antigenic and allergenic properties of the storage mite Tyrophagus putrescentiae.

The antigens and allergens in the storage mite Tyrophagus putrescentiae, commonly found in grain and hay and sometimes in house dust, were characterized by crossed immunoelectrophoresis and crossed radioimmunoelectrophoresis. Three mite extracts, T. putrescentiae (TP) mite bodies, feces, and a combination of mites, feces, and culture medium (TP + CM) were studied. TP and TP + CM (primarily feces) extracts exhibited 20 and 18 antigens, respectively. By use of serum from two skin test-positive patients, autoradiograms demonstrated TP contained two allergens and TP + CM contained five allergens, three of which probably originated from feces. CM (whole wheat flour) did not stimulate antibody production in rabbits. TP feces shared 10 antigenic determinants with TP and 14 with TP + CM. Two antigens common to TP feces and TP were also shared allergens.

Allergens↗
PubMed1985

Allergens of the house dust mite Dermatophagoides farinae--immunochemical studies of four allergenic fractions.

Analysis of the allergenic components of the house dust mite Dermatophagoides farinae was performed. Four different types of proteins reactive with human anti-mite IgE antibodies were identified as four distinct radioprecipitins in radioimmunoelectrophoresis. These were designated as mite allergen reactive with human IgE antibodies (Me) Me 1, Me 2, Me 3, and Me 4 according to their electrophoretic mobility from the slower to the faster. Me 1 and Me 2 were the first and the second prevailing allergens, respectively, in 133 atopic patients subjected to the study. Me 1, on purification by gel filtration and anion exchange chromatography, elicited a single radioprecipitin by radioimmunoelectrophoresis. Me 1 also elicited a single band in sodium dodecyl sulphate-polyacrylamide gel electrophoresis and a single peak in high-performance liquid chromatography. Both methods elicited identical values of 17,000 daltons for the molecular weight of Me 1. The isoelectric point of Me 1 was suggested to be 8.0. Me 1 elicited higher skin reactions compared to that obtained by the crude mite extract when it was assessed in seven atopic patients by serial titration intradermal skin testing.

Allergens↗
PubMed1985

An immunochemical approach to indoor aeroallergen quantitation with a new volumetric air sampler: studies with mite, roach, cat, mouse, and guinea pig antigens.

We describe a new high-volume air sampler for determining antigen concentrations in homes and illustrate its use for quantitating airborne house dust mite, cat, cockroach, mouse, and guinea pig antigens. The concentration of house dust-mite antigen was similar from houses in Rochester, Minn. and tenement apartments in Harlem, N. Y., but cockroach and mouse urinary proteins were present only in Harlem. The amount of cat or guinea pig antigen varied as expected with the number of pets in the home. In calm air the airborne concentration of mite and cat antigen was similar throughout the house but increased greatly in a bedroom when bedding was changed. In calm air most of the cat and mite antigens were associated with respirable particles less than 5 microns mean aerodynamic mass diameter, but in air sampled after the bedding was changed, more cat antigen was found in particles greater than 5 microns. The apparatus and technique described can provide objective data concerning the magnitude and the relative distribution and duration of suspended particles of defined sizes, which contain allergen activity.

Air Pollutants↗
PubMed1992

The role of water temperature and laundry procedures in reducing house dust mite populations and allergen content of bedding.

The effects of various laundry procedures on house dust mites and their allergens have been established. All mites were killed by water temperatures 55 degrees C or greater. Killing at lower temperatures was not enhanced by any of the pure detergents or laundry products tested. A cold cycle of laundry washing with or without laundry powder did not remove most live mites from bedding, however, the allergen concentration (Der p I/gm fine dust) was reduced by more than 90%. Dry cleaning did not reduce the allergen concentration of the dust, although most, if not all, mites were killed.

Allergens↗
PubMed1994

Seasonal variation in airway hyperresponsiveness and natural exposure to house dust mite allergens in patients with asthma.

Nonspecific airway hyperresponsiveness is a fundamental characteristic of patients with asthma and can be influenced by several stimuli. In nine patients with asthma and an isolated allergy to house dust mite, the variation of natural exposure to the house dust mite allergen Der p I and the corresponding changes in nonspecific airway hyperresponsiveness were followed up for 1 year. The concentration of Der p I in floor dust from living rooms and bedrooms (as a measure of exposure) reached maximum levels in late summer and the beginning of autumn (August to October), whereas the lowest levels were found during the months of March to May (delta Der p I = +2.31 micrograms/gm and -1.33 micrograms/gm respectively, both compared with the year average). Airway hyperresponsiveness (as measured by the provocative concentration of histamine causing a 20% fall in forced expiratory volume in 1 second [PC20] threshold) also showed a seasonal variation, with most severe hyperresponsiveness during the months of August to November, almost the same period in which the exposure to house dust mite allergens reached maximal levels (delta PC20 histamine = -1.47 mg/ml in November vs +1.79 mg/ml in March, both compared with the year average). Our results support the view that seasonal changes of exposure to environmental allergens such as house dust mite allergens will have an effect on the level of airway hyperresponsiveness in patients with allergic asthma.

Adult↗