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At least 847 records · Page 47Linked to original sources
PubMed2000

Pollen availability for predaceous mites on apple: spatial and temporal heterogeneity.

It has been suggested that an abundance of alternate food early in the spring may be critical to the ability of generalist predaceous mites to suppress spider mite pests. One alternate food that is typically very abundant in spring is wind-dispersed pollen. Here we investigate, at several spatial scales, the heterogeneity in the availability of pollen to predaceous mites on apple. We found pollen to be abundant on apple leaves very soon after they opened (> 100 grains/cm2), and that the dominant pollen types at this time were wind-dispersed tree pollens (Betulaceae and Pinaceae). We found that most of the spatial variation in pollen abundance occurred at either small spatial scales (within trees) or very large spatial scales (among orchard blocks). Variability among orchards was clearly influenced by the surrounding vegetation, and probably also by the management regime (frequency of mowing). Spatial heterogeneity in pollen availability may affect the build-up of predatory mite populations in the spring, as we found early season abundances of Typhlodromus pyri (Phytoseiidae) and Zetzellia mali (Stigmaeidae) to be better correlated with early season pollen density than with abundance of mite prey (Aculus schlechtendali).

Animals↗
PubMed1999

Assessment of Amblyseius fallacis (Acari: Phytoseiidae) for biological control of tetranychid mites in an Ontario peach orchard.

We introduced a mass-reared pyrethroid-resistant strain of the predatory phytoseiid mite Amblyseius fallacis (Garman) into an Ontario peach orchard in an attempt to control populations of the phytophagous mites Panonychus ulmi Koch and Tetranychus urticae Koch (Acari: Tetranychidae). Releases of 1,000 and 2,000 mites per tree were made, at three different times. The release of 2,000 mites per tree in June and in July resulted in significantly higher phytoseiid densities than was observed on control trees. However, densities of P. ulmi or T. urticae were not significantly affected by any release rate or by timing. The release of 1,000 A. fallacis per tree, or of any density in August, did not significantly increase phytoseiid abundance. In the following year, population dynamics of both phytoseiid and phytophagous mites were not significantly affected by the previous year's release. Amblyseius fallacis can be a useful predator in some fruit orchards. However, further research is necessary into the timing and rate of release, modified spray programmes, and with different crops, in order to clarify the role of this species for biological control in Ontario peach orchards.

Aerosols↗
PubMed2002

Bulbs mycoflora and their relation with three stored product mites.

The distribution of moulds on stored and field onion and garlic plants infested by bulb mites in Assiut area (Egypt) was studied using PDA medium at 28 degrees C. Among 40 host samples and the three mite species tested no significant difference was noted in the contamination by moulds. A total of 20 species appertaining to 11 genera were identified from the tested mites and their habitats. The predominant moulds on all samples were "storage moulds" from the genera Aspergillus (A. niger, A. versicolor) and Penicillium (P. chrysogenum, P. funiculosum, and "field moulds" among which Alternaria, Cladosporium, Fusarium (and its teleomorphs) and Setosphaeria were encountered most frequently. One fungus well known facultative pathogen was obtained: Beauveria bassiana. The tested mites transfer A. niger, N. haematococca, R. stolonifer and P chrysogenum outside their bodies while, A. flavus and A. ochraceus transfer through their digestive tracts along with the foods. Individuals of all mites could survived till the end of the experiment on all fungal species tested except A. niger, A. ochraceus and A. sydowii. Among 48 isolates screened for their ability to produce chitinase, about 83% of the isolates could produce this enzyme. Most of the positive isolates (17 isolates) had moderate producers

Animals↗
PubMed2001

Effect of insecticides and fungicides on the interaction between members of the mite families Phytoseiidae and Stigmaeidae on citrus.

The study was carried out to evaluate the effect of some insecticides and fungicides on the interaction between predacious mites of the families Phytoseiidae and Stigmaeidae on citrus. Euseius citrifolius Denmark and Muma, Euseius concordis (Chant) (Phytoseiidae), and Agistemus aff. bakeri (Stigmaeidae) were the most abundant species of predacious mites. No significant reduction of the population of stigmaeids was detected following the pesticide treatment. On the contrary, the population of those mites increased after the application of methidathion, petroleum oil, deltamethrin, cupric oxychloride and cuprous oxide, as compared to the population of those mites in the control plots. The chemicals promoting increased stigmaeid populations are some of those that promoted reduction of phytoseiid populations. A significant negative correlation was found between the numbers of phytoseiids and stigmaeids on citrus leaves immediately before treatments, and 33, 50, 83 and 105 days after treatment. A clear negative linear correlation between the number of predacious mites from both families was detected for benomyl, cupric oxychloride, cuprous oxide, thiophanate methyl, and control. Phytoseiid-stigmaeid interaction on citrus orchard is discussed.

Animals↗
PubMed2002

Importance of ambient saturation deficits in an epizootic of the fungus Neozygites floridana in cassava green mites (Mononychellus tanajoa).

The mite-pathogenic fungus Neozygites floridana Fisher (Entomophthorales: Neozygitaceae) is considered to have potential for the biological control of the cassava green mite, Mononychellus tanajoa (Bondar). However, its activity is sporadic and laboratory data suggest a strong dependence on night-time saturation deficits for transmission. We report on an epizootic of this fungus in a mite population in northeastern Brazil. During the epizootic, host populations appeared to he limited by a combination of the pathogen and a predatory mite Neoseiulus idaeus (Acari: Phytoseiidae). When temperatures increased, the epizootic finished and the host population began to grow. Abiotic conditions could not explain the variation in host mortality following pickup of infective propagules in this epizootic. However, night-time saturation did help to explain the variation in transmission from infective cadavers to newly killed hosts. This supports laboratory observations that horizontal transmission between hosts is determined mainly by saturation deficits, while the process of infection is little affected by abiotic conditions. A further field observation was the near-absence of resting spores in dead mites (ca. 0.1% of cadavers), suggesting that the pathogen population was unsuccessful in producing inoculum to infect future M. tanajoa populations. The implications are that this pathogen will only be effective as a biological control agent in periods of high relative humidity, and establishment in new areas may be limited by resting spore formation.

Animals↗
PubMed2002

Mite growth on fungus under various environmental conditions and its potential application to biofilters.

The effects of relative humidity, temperature, pH and vapor-phase toluene concentration on Tyrophagus putrescentiae growth on Cladophialophora sp. were tested in controlled environmental chambers. It was observed that the mites were able to reproduce readily at relative humidities between 90% and 97% as well as on porous perlite support material pre-soaked in nutrient media of pH 2.5, 4 and 7. Also, the presence of toluene at gas-phase concentrations of 500 to 2000 mg m(-3) was found to be non-toxic to the mites. The mites, however, were unable to maintain a large population when the temperature was maintained at 14 degrees C, and overpopulation of the living space led to declines in mite population over time. Overall, it was found to be relatively simple to cultivate mites that may be used for fungal biomass control measures in biofilter applications.

Animals↗
PubMed2004

Efforts to control mites on Iberian ham by physical methods.

This study is aimed at the development of a method for integrated mite control in the industrial production of Iberian and Alentejan ham. The investigations were carried out on the premises of five factories in the southwest of the Iberian Peninsula. Tyrophagus longior was predominant on hams in the drying rooms, Tyrophagus putrescentiae in cellars, while Tyrolichus casei was observed only in one factory, together with Melichares dendriticus (Acari: Ascidae), a predator of tyroglyphids. Relative humidity levels below 60% reduced the growth of mites on the ham surface, but these conditions forced the mites to seek refuge: T. putrescentiae and T. casei were found in cavities inside the ham. At the end of the experimental curing period, 11% of the hams were totally disintegrated by mite damage inside. Mites survived high-temperature treatments which are detrimental to the hams: 71 degrees C, 11 min; 57 degrees C, 30 min and 40 degrees C, 96 h. They also survived a long low-humidity period: 1 month at 18 degrees C and 32% R.H.

Animals↗
PubMed2004

Environmental parameters determining water mite assemblages in Costa Rica.

This paper presents an ecological analysis of the water mite fauna of 350 streams, rivers, springs and standing waters from all main regions, ecosystems and elevations in Costa Rica. From 509 sample sites about 20,000 water mites representing 74 genera in 21 families were collected. 17 habitat types were distinguished and 11 further environmental parameters were measured. The significance of the particular parameters was analysed using canonical correspondence analysis (CCA). Habitat type, elevation, temperature and velocity were identified as major factors determining water mite assemblages. The analyses showed the existence of characteristic water mite coenoses in different neotropical habitats and the suitability of neotropical water mites for bio-monitoring programmes.

Altitude↗
PubMed2004

The role of methyl salicylate in prey searching behavior of the predatory mite phytoseiulus persimilis.

Many carnivorous arthropods use herbivore-induced plant volatiles to locate their prey. These plant volatiles are blends of up to hundreds of compounds. It is often unknown which compounds in such a complex volatile blend represent the signal to the foraging carnivore. We studied the role of methyl salicylate (MeSA) as part of the volatile blend in the foraging behavior of the predatory mite Phytoseiulus persimilis by using a Y-tube olfactometer. MeSA is one of the compounds released by lima bean, infested with Tetranychus urticae--a prey species of the predatory mite. MeSA attracted satiated predatory mites in a dose-dependent way with optimum attraction at a dose of 0.2 microg. Predatory mites did not discriminate between a prey-induced lima bean volatile blend (that contains MeSA) and a prey-induced volatile blend to which an extra amount of synthetic MeSA had been added. However, they preferred a MeSA-containing volatile blend (induced by T. urticae) to an otherwise similar but MeSA-free blend (induced by jasmonic acid). Adding synthetic MeSA to the MeSA-free blend significantly increased the mites' choice for this odor, suggesting an important role for MeSA. This study is a new step toward unraveling the role of herbivore-induced plant volatiles in the foraging behavior of predatory arthropods.

Animals↗
PubMedDate not supplied

The prevention and incidence of asthma and mite allergy (PIAMA) birth cohort study: design and first results.

The Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study was initiated in 1996. Children born to allergic mothers were enrolled in a double-blind placebo-controlled trial for evaluating the use of mite-impermeable mattress and pillow covers. Children born to allergic and non-allergic mothers were enrolled in a 'natural history' study to assess the role of environmental and dietary risk factors for the development of allergic disease in childhood. Recruitment started by distributing a validated screening questionnaire among >10,000 pregnant women during their first visit to a prenatal health clinic. Allergic mothers-to-be were invited to participate in the intervention study. Allergic, and a random sample of non-allergic, mothers-to-be were invited to participate in the 'natural history' arm of the study. In the intervention study, homes were visited before birth, 3 months after birth, and 12 months after birth for the collection of dust samples from floors and mattresses. In addition, the homes of about one-third of the children in the 'natural history' part of the study were visited for dust collection when the children were 3 months of age. The intervention study started with 855 participants and the 'natural history' study with 3,291 participants. Follow-up at 3 years of age has now been completed with satisfactory compliance (>90%). A medical investigation and home visit at 4years of age are nearing completion. Preliminary results show that mite-allergen levels were lower than found in previous Dutch studies, and that the intervention measure had a significant effect on mite-allergen levels, without important clinical benefits up to age 2 years old. The allergic families lived in homes with fewer 'triggers' such as pets, smoking and carpets than the non-allergic families, regardless of the intervention. The ongoing PIAMA cohort study will probably reveal useful information concerning effects of allergen load and reduction in the setting of a relatively low mite-allergen exposure, as well as other variables on the development of allergic manifestions and asthma.

Air Pollution, Indoor↗
PubMed2001

Double-blind placebo-controlled house dust mite control measures in adult patients with atopic dermatitis.

BACKGROUND: Avoidance of allergens has been shown to be of benefit in patients with atopic asthma sensitized to indoor allergens. In atopic dermatitis, there is so far little information about the effect of house dust mite elimination strategies. OBJECTIVES: We therefore performed a randomized controlled study of house dust mite control in patients with this disease. METHODS: Twenty adult patients with moderate to severe atopic dermatitis were included. Inclusion criteria were a positive RAST to house dust mite antigen (CAP class > 3) and a concentration of > 2 microg g(-1) of the house dust mite antigen Der p1 in the patient's mattress dust. Patients were randomized to either the active treatment group (allergen-impermeable mattress encasing, acaricide spray containing tannic acid and benzylbenzoate) or a control group (allergen-permeable encasing, spray containing water and traces of ethanol). Severity of disease was estimated every 2 months by an established score (SCORAD), and eosinophil cationic protein (ECP) in the serum was determined by enzyme-linked immunosorbent assay. Furthermore, the use of topical steroids was quantified. Patients assessed daytime pruritus and pruritus-induced sleeplessness weekly on a visual analogue scale. The study lasted 1 year. RESULTS: At the end of the study, the active treatment group showed a statistically significant reduction in Der p1 exposure as compared with the control group. However, when comparing the change from the start to the end of the study, there was no statistically significant difference between active treatment and control groups as measured by the SCORAD score and by ECP levels in the serum. Some patients in the active treatment group reported less pruritus-induced sleeplessness, but there was no statistically significant difference between the two treatment groups. CONCLUSIONS: For adult patients with atopic dermatitis it was shown that 1 year of house dust mite avoidance reduced the allergen exposure, but an improvement of overall disease activity was not demonstrated.

Adolescent↗
PubMed1998

Mechanical ventilation protects one-storey single-dwelling houses against increased air humidity, domestic mite allergens and indoor pollutants in a cold climatic region.

BACKGROUND: Poor ventilation in modern, highly insulated housing is an important factor in promoting indoor humidity levels to exceed 7 g/kg in cold climatic regions. OBJECTIVE: To investigate the ventilation rate in houses with different ventilation systems in relation to indoor air humidity, domestic mite allergen levels and volatile organic compounds (VOC). METHODS: Measurements were performed regarding ventilation rate, indoor temperature, air humidity, mattress mite allergen concentrations using enzyme-linked immunosorbent assay and total indoor VOC in 59 similarly constructed one-storey single-dwelling houses. In 22 of the houses, a mechanical supply and exhaust ventilation were installed after construction. RESULTS: In only five of the houses with mechanical supply and exhaust ventilation the air exchange rate per hour (ACH) was below 0. 5 compared with 24 of the 29 houses with natural ventilation (OR = 0. 06, CI 95% 0.01-0.2). None of the 23 houses with an ACH >/= 0.5 had an absolute indoor humidity (AIH) of 7 g/kg air or more, compared with 10 of the 36 houses with an ACH < 0.5 (P = 0.01 ). In none of the 23 houses with an ACH >/= 0.5 were concentrations of mite allergen exceeding 2 microg/g of dust found, compared with six of the 36 houses (17%) with an ACH below 0.5 (P = 0.04). Further, 10 of the 34 houses with a total VOC exceeding 200 microg/m3 had mite allergen in mattress dust exceeding 0.5 microg/g, compared with one of the 22 houses with VOC < 200 microg/m3 (P = 0.04). CONCLUSION: The study shows that in modern, highly insulated, one-storey single-dwelling houses in cold temperate regions, mechanical ventilation increases the possibility of reaching an ACH of >/= 5 which protects against indoor humidity levels contributing to mite survival as well as high levels of indoor air pollutants in winter.

Air Pollution, Indoor↗
PubMed1999

Allergenic differences between the domestic mites Blomia tropicalis and Dermatophagoides pteronyssinus.

BACKGROUND: House dust mite allergens are the most important indoor allergens associated with asthma and rhinitis in Singapore and the tropics. Recent data to suggest that besides the Dermatophagoides spp., the domestic mite Blomia tropicalis (Bt) is also an important source of allergens in these regions. OBJECTIVE: To evaluate the degree of allergenic cross-reactivity between Bt and D. pteronyssinus (Dp). METHODS: Cross-reactivity between extracts of Bt and Dp was evaluated by fluorescent allergosorbent (FAST) inhibition studies and cross enzyme immunoelectrophoresis. Additionally, the major Dp allergens - Der p 1, Der p 2 and Der p 5, were also compared with the Bt extract by dot blot inhibition. Skin prick and intradermal end-point titration were then carried out to compare the homologous allergens of the mite species, Blo t 5 and Der p 5. RESULTS: FAST inhibition studies showed low to moderate cross-reactivity between the two dust mite extracts (maximum cross-inhibition, 60%). Native allergens studied by cross enzyme immunoelectrophoresis using mite allergic sera also showed similar results but with at least four cross-reactive IgE binding antigens. Dot blot inhibition studies using allergens of Dp, Der p 1, Der p 2, and Der p 5, showed little cross-reactivity between these allergens with components of the crude Bt extracts. Further, evaluation of a recombinant allergen of Bt, Blo t 5, showed low levels of cross-reactivity even with its homologous Dp counterpart, Der p 5. CONCLUSION: These results provide evidence that Bt allergens are distinct and have relatively low to moderate cross-reactivity with Dermatophagoides spp. allergens. Bt allergens should therefore be included in the diagnostic panel for the evaluation of allergic disorders in the tropics, and the development of new diagnostic and therapeutic strategies should include allergens of Bt.

Allergens↗
PubMed2003

Cloning and expression of Blo t 1, a novel allergen from the dust mite Blomia tropicalis, homologous to cysteine proteases.

BACKGROUND: House dust mite allergens have been shown to be a very important stimulus in the causation of asthma and triggers for the exacerbation of symptoms. Therefore, characterization of mite-derived allergens at the molecular level is an important step for the development of effective diagnostic and therapeutic approaches, as well as for epidemiological studies. OBJECTIVE: To clone, express and characterize at the molecular level the cysteine protease from Blomia tropicalis (Bt). METHODS: A full-length cDNA encoding Blo t 1 was cloned from a Bt cDNA library using a PCR and RACE-based strategy. The cDNA was PCR-amplified, sequenced and subcloned into a prokaryotic expression vector. The allergenicity of the recombinant Blo t 1 was evaluated for IgE reactivity by Western blot. RESULTS: Blo t 1 cDNA encodes a 221 amino acids polypeptide with an estimated molecular weight of 25 kDa. The recombinant protein is 35% identical to other mite cysteine proteases. Recombinant Blo t 1 (rBlo t 1) bound IgE from 62% of Bt skin test-positive serum. Dermatophagoides pteronyssinus (Dp) skin test-positive sera did not react with rBlo t 1, indicating the possible presence of unique IgE epitopes on the rBlo t 1 molecule. A three-dimensional image of Blo t 1, constructed based on predicted analysis, showed conserved secondary and tertiary structure with other cysteine proteases. CONCLUSION: We report the cloning, expression and IgE reactivity of Blo t 1, a novel allergen from the domestic mite Blomia tropicalis (Bt), highly homologous to cysteine proteases. This putative cysteine protease, designated Blo t 1, may play a major role as an immunodominant allergen involved in dust mite-specific IgE-mediated hypersensitivity.

Allergens↗
PubMed2001

Commercial availability of a house dust mite patch test.

The house dust mite long has been studied for its potential role in atopic dermatitis. Its part in the pathogenesis of asthma and allergic rhinitis has been studied and is accepted. Testing for the dust mite allergen in this arena is performed with radioallergosorbent tests (RASTs) and prick testing. For several reasons, including the lack of a standardized testing tool, the difficulty in removing dust from the environment and the lack of association of dust and skin disease by patients, the role of the house dust mite in the pathogenesis of atopic dermatitis and skin disease has been questioned. Chemotechnique Diagnostics (Malmo, Sweden) now provides a standardized dust mite allergen in petrolatum in 2 concentrations. Dermatophagoides mix is a 50:50 mix of Dermatophagoides pteronyssinus and D. farinae at concentrations of 20% and 30%. The availability of a standardized patch test allergen for the house dust mite provides a better tool to investigate the role of this allergen as a contactant.

Animals↗
PubMed2002

Harmful effect of immunotherapy in children with combined snail and mite allergy.

BACKGROUND: With respect to allergy, the possibility of cross-reactivity between snail and mite is well recognized, and anecdotal reports suggesting that allergen immunotherapy with mite extract can worsen snail-induced allergy exist. OBJECTIVE: We describe the effect of immunotherapy in 4 children with snail-mite allergy. METHODS: Four children (1 boy and 3 girls; 9-13 years of age) had consistent clinical histories (mild immediate respiratory symptoms after ingestion) and positive skin reactions for allergy to snail. They also had mite-induced asthma and were therefore prescribed subcutaneous specific immunotherapy and subsequently followed. RESULTS: Several months (8-25) after starting immunotherapy, all children experienced life-threatening reactions, anaphylaxis, and respiratory failure after inadvertent ingestion of snail. Skin reactivity to the fresh food increased in all patients. CONCLUSIONS: This observation confirms that in patients with combined mite-snail allergy, immunotherapy should be avoided.

Adolescent↗
PubMed1989

Cloning and sequencing of a cDNA expressing a recombinant house dust mite protein that binds human IgE and corresponds to an important low molecular weight allergen.

A cDNA clone coding for a mite allergen of mol wt approximately 14,000 has been isolated and its DNA sequence determined. The native component from mite extracts encoded by this DNA was identified by immunoprobing blots of mite body extract with human IgE eluted from the electroblotted cloned fusion polypeptides derived from the expressed cDNA clone. The clone encodes a polypeptide with a deduced mol wt of 17,460. The deduced amino acid sequence was not homologous to any known protein sequences and it contains no cysteine or tryptophan. On blots, 21 of 38 sera from mite-allergic subjects recognized the cloned material, and this recognition strongly correlated with IgE-binding to the native component on protein blots of mite extract.

Allergens↗
PubMed1995

A major house dust mite allergen disrupts the immunoglobulin E network by selectively cleaving CD23: innate protection by antiproteases.

Asthma is a chronic life-threatening disease of worldwide importance. Although allergic asthma and related atopic conditions correlate strongly with immune sensitization to house dust mites, it is unclear why antigens from mites provoke such powerful allergic immune responses. We have characterized the protease activity of Der p I, the group I protease allergen of the house dust mite Dermatophagoides pteronyssinus, and here report that it cleaves the low-affinity immunoglobulin (Ig) E Fc receptor (CD23) from the surface of human B lymphocytes. Der p I selectively cleaves CD23 and has no effect on the expression of any other B cell surface molecules tested. We speculate that this loss of cell surface CD23 from IgE-secreting B cells may promote and enhance IgE immune responses by ablating an important feedback inhibitory mechanism that normally limits IgE synthesis. Furthermore, since soluble CD23 is reported to promote IgE production, fragments of CD23 released by Der p I may directly enhance the synthesis of IgE. alpha 1-Antiprotease, a pulmonary antiprotease, is also shown to inhibit the cleavage of CD23 by Der p I. This may be significant in the etiopathogenesis of asthma, because other indoor pollutants associated with asthma are known to potently inhibit this antiprotease. These data suggest that the proteolytic activity of Der p I, the group I allergen of the house dust mite D. pteronyssinus, is mechanistically linked to the potent allergenicity of house dust mites. Furthermore, inhibition of Der p I by alpha 1-antiprotease suggests a mechanism by which confounding factors, such as tobacco smoke, may act as a risk factor for allergic asthma.

Animals↗