Contact allergy: another occupational risk to Tetranychus urticae

Microscopic Menaces: The Impact of Mites on Human Health

Mites are highly prevalent arthropods that infest diverse ecological niches globally. Approximately 55,000 species of mites have been identified but many more are yet to be discovered. Of the ones we do know about, most go unnoticed by humans and animals. However, there are several species from the Acariformes superorder that exert a significant impact on global human health. House dust mites are a major source of inhaled allergens, affecting 10-20% of the world's population; storage mites also cause a significant allergy in susceptible individuals; chiggers are the sole vectors for the bacterium that causes scrub typhus; Demodex mites are part of the normal microfauna of humans and their pets, but under certain conditions populations grow out of control and affect the integrity of the integumentary system; and scabies mites cause one of the most common dermatological diseases worldwide. On the other hand, recent genome sequences of mites provide novel tools for mite control and the development of new biomaterial with applications in biomedicine. Despite the palpable disease burden, mites remain understudied in parasitological research. By better understanding mite biology and disease processes, researchers can identify new ways to diagnose, manage, and prevent common mite-induced afflictions. This knowledge can lead to improved clinical outcomes and reduced disease burden from these remarkably widespread yet understudied creatures.

Epidemiology of spider mite sensitivity: a meta-analysis and systematic review

Background

Spider mites, including Tetranychus urticae, Panonychus citri, and Panonychus ulmi, are common pests in gardens, greenhouses, and orchards. Exposure, particularly occupational exposure, to these organisms may lead to the development of respiratory or contact allergies. However, the prevalence of sensitivity to spider mites is unclear.

Methods

We examined the literature to generate an estimate of the global prevalence of allergies to spider mites.

Results

Electronic databases were searched and twenty-three studies reporting the prevalence of sensitivity to spider mites (based on skin prick tests or IgE-based detection systems) in an aggregate total of 40,908 subjects were selected for analysis. The estimated overall rate of spider mite sensitivity was 22.9% (95% CI 19–26.8%). Heterogeneity was high and meta-regression analysis considering variables such as published year, country, number of study subjects, methods for allergen detection (skin prick test, ImmunoCAP, RAST testing, or intradermal test), and mite species revealed no single significant source. Twelve of the 23 studies reported rates of monosensitization (i.e., patients responsive to spider mites but no other tested allergen), yielding a global average of 7% (95% CI 5–9%), hence spider mites represent a unique source of allergens.

Conclusions

Spider mites are an important cause of allergic symptoms. However, the publication bias and heterogeneity evident in this study indicate that further trials using standardized detection methods are needed to determine the association of exposure and symptoms as well as the specific patient characteristics that influence developing spider mite sensitivity.

Comparisons of the allergenic mite prevalence in dwellings and certain outdoor environments of the Upper Silesia (southwest Poland)

The occurrence of allergenic mites (pyroglyphid house-dust mites, acarid and glycyphagid storage mites and others) in dwellings and in synanthropic outdoor sites in a densely populated urban area was investigated. A total of 335 house dust samples were collected from dwellings at 7 different locations in Upper Silesia (Poland), including 84 samples from dwellings of Katowice. Mites were found in 188 of the samples examined (56.1%). A total of 4410 mite specimens were isolated and identified, including 4212 members of the family Pyroglyphidae (95.51%). Among them, Dermatophagoides farinae was predominant (75.3%), followed by D. pteronyssinus (18.6%) and Euroglyphus maynei (1.5%). Moreover, litter soiled with communal wastes was sampled. All 86 samples contained mites. A total of 7547 mite specimens were isolated including 6050 mites known as allergenic (80.5%). Among the astigmatid mites two acarids were dominant: Tyrophagus silvester and T. longior (28.7% and 25.1% of all mites). It should be stressed that 6 of the acarid mite species or genera found in outdoor environments are typical domestic mites (T. putrescentiae), or they have been collected from house dust samples (T. longior, Tyrolichus casei, Thyreophagus entomophagus, Mycetoglyphus fungivorus and Rhizoglyphus robini). The litter of synanthropic sites can therefore form a substantial source of infestation.

Mite allergens

There is an increasing awareness of the health implications of mite sensitivity, as it is closely related to asthma. Mite allergy constitutes a complex worldwide problem, with sanitary and economical implications. Not only are mite species present in house dust, producing potent allergens, but other, less studied species are also responsible for significant allergic reactions in occupational settings. In this review, we focus on the growing number of mite species that are implicated in allergic cutaneous and respiratory diseases in humans. Mite allergy is not restricted only to the human "indoor" environment, because numerous reports clearly demonstrate that many species that can induce sensitization and symptoms are encountered in occupational settings. An important component of allergy research is the evaluation of the allergenic cross-reactivity to verify to what extent different mite species have unique, species-specific, or cross-reactive allergens. The results of these investigations have important clinical consequences for the diagnosis and treatment of allergic diseases. Internationally standardized mite extracts are needed to compare sensitization rates around the world and clearly establish risk factors associated with sensitization and asthma. In spite of recent controversial results, a significant reduction in the exposure to mite allergens continues to be an important challenge and one of the main goals in the treatment of mite-induced respiratory symptoms. In many cases, this reduction must be achieved in the workplace as well as in the home environment.

Relationship between total and allergen-specific IgE serum levels and presence of symptoms in farm workers sensitized to Tetranychus urticae

BACKGROUND

Clinical complaints in atopic subjects with asthma and rhinitis occur more frequently in the presence of high total and allergen-specific IgE serum levels. Here we report on the relationship between total and allergen-specific IgE serum levels and presence of symptoms in an unselected farmer population sensitized to Tetranychus urticae (TU).

METHODS

Farmers were recruited as previously described. Total IgE and allergen-specific IgE were measured by immunoassay in TU-positive skin prick test (SPT) farmers (n = 58) and two control groups including Dermatophagoides pteronyssinus (Dp)-positive SPT subjects (n = 40) and non-atopic, TU-negative SPT healthy farmers (n = 25).

RESULTS

Both TU+ and Dp+ subjects had significantly higher total IgE values (P < 0.001) than healthy non-atopic subjects. TU-specific IgE levels were significantly more elevated in symptomatic than non-symptomatic TU+ subjects (P = 0.028). Dp-specific IgE levels were higher in symptomatic than non-symptomatic Dp+ subjects (P = 0.003). Finally, total IgE levels were significantly higher in the symptomatic than non-symptomatic subgroups in both TU+ and Dp+ subjects (P < 0.0001 and P = 0.007, respectively). Logistic regression analysis showed that only total IgE concentrations were significant predictors of current symptoms in TU+ subjects.

CONCLUSIONS

High total IgE and allergen-specific IgE levels are associated with symptoms in TU+ subjects. Definition of their predictive value requires further studies.

Two-spotted spider mite allergy: immunoglobulin E sensitization and characterization of allergenic components

BACKGROUND AND OBJECTIVE

Previous investigations demonstrated that two-spotted spider mite (TSM) inhalation causes allergic asthma in agricultural workers. This work investigates whether TSM causes similar problems in the urban population. We determined the sensitization rate to TSM. We also identified immunoglobulin (Ig)E-binding components and evaluated their relationship with house-dust mite (HDM) allergens.

METHODS

We carried out skin prick test (SPT) with TSM in 1,806 respiratory allergy patients over 1 year. TSM-IgE was detected by enzyme-linked immunoadsorbent assay (ELISA). TSM-sensitized patients were classified into two groups: patients who were skin test-positive to both TSM and HDM were included in group A and patients who were skin test-positive to TSM only were included in group B. ELISA inhibition test using sera from group A and B were conducted. IgE-immunoblotting was used to identify major allergens. These were purified by 2-dimensional electrophoresis and blotted onto polyvinylidene difluoride, and N-terminal sequences were identified.

RESULTS

SPT (> or = 2+ of allergen/histamine) was positive in 358 (19.8%) patients. Twelve (6.6%) showed positive response to TSM only, and 54.5% had positive specific IgE. ELISA inhibition test using sera from two groups showed significant inhibition by TSM with minimal inhibition by HDM. Amino acid sequence of three major allergens was not homologous with any previously characterized allergens.

CONCLUSION

IgE-sensitization rate to TSM was 19.8% in respiratory allergy patients. Eleven IgE-binding components and three major allergens were identified. The pIs and amino acid sequences of the major allergens were determined.

Spider-mite allergy and asthma in fruit growers

Asthma and allergic diseases caused by domestic mites such as house dust mites and storage mites are major health problems worldwide. In contrast to domestic mites, spider mites are outdoor phytophagous mites causing significant damage to fruit leaves throughout the world. After several case reports of spider mite-induced asthma and allergy, cross-sectional surveys have demonstrated that spider mites are important allergens in the development of asthma and rhinitis in fruit farmers. Interestingly, epidemiological surveys have also demonstrated that spider mites are common sensitizing allergens that are related to the prevalence of asthma and rhinitis, even in the non-farming population exposed to spider mites. Protein analysis has demonstrated that crude extracts derived from spider mites contain several major allergens, and that N-terminal amino acid sequencing of the major allergens is not homologous with any previously characterized domestic mite allergens, suggesting that major allergens derived from spider mites are unique in terms of cross-reactivity to domestic mites. Taken together, these findings suggest that spider mites are important allergens in the development of asthma among the exposed non-farming population as well as among fruit farmers themselves, and that allergens derived from spider mites may be novel allergens.

Epidemiology of allergic occupational diseases induced by Tetranychus urticae in greenhouse and open-field farmers living in a temperate climate area

BACKGROUND

The role of Tetranychus urticae (TU) as an occupational allergen has thus far been investigated only in selected farmer samples.

METHODS

The prevalence of TU-induced sensitization and occupational diseases in a randomized sample of farmers living in a temperate climate area was investigated. Occupational/nonoccupational symptoms, skin prick test (SPT) results with common allergens and TU, specific occupational test results, and greenhouse or open-field sources of TU exposure were assessed. The study design was cross-sectional.

RESULTS

The prevalence of positive SPT to TU was 6%. TU-induced allergic/nonallergic complaints accounted for 65% of farmers with challenge-confirmed occupational disease. In all farmers, sensitization to common allergens was a risk factor for both current occupational and nonoccupational complaints, while TU sensitization was a prominent risk factor for occupational complaints. Furthermore, in SPT-positive farmers, only the presence of seasonal occupational complaints was significantly associated with TU sensitization. Common allergen sensitization was a risk factor for development of TU sensitization, which was more frequent in greenhouse than in open-field workers.

CONCLUSIONS

TU was a common nontraumatic, allergic occupational hazard for farmers. Since occupational seasonal symptoms could be directly related to the presence of TU sensitization, allergy to this mite should be routinely investigated in farmers.

Two-spotted spider mite (Tetranychus urticae): an important allergen in asthmatic non-farmers symtomatic in summer and fall months

BACKGROUND

The Tetranychus urticae (two-spotted spider mite, TSM) is a spider mite commonly found on fruit trees, herbaceous plants, and greenhouse flowers.

OBJECTIVE

To evaluate the clinical significance of TSM-derived allergens in non-farmers with asthma living around pear orchards, and to assess the allergenic relationship with house dust mite.

METHODS

Skin prick tests with TSM were performed in 50 asthmatic non-farmers living around pear orchards. The serum TSM-specific IgE was measured in the 16 asthmatics with a positive skin response to TSM. To diagnose TSM-induced asthma, specific bronchial challenges with TSM were performed in the 16 asthmatics. ELISA inhibition tests were performed to assess the allergenic cross-reactivity with house dust mites.

RESULTS

Ten of the 16 asthmatics with positive skin responses to TSM showed a significant bronchoconstriction following inhalation of TSM. Eight of the ten TSM-induced asthmatics had high serum TSM-specific IgE and one showed a positive skin response only to TSM. Their asthmatic symptoms were aggravated seasonally, especially in summer and early fall. On ELISA inhibition tests, partial inhibitions with D. pteronyssinus antigens were noted in sera from five asthmatics with positive skin responses to both TSM and D. pteronyssinus, although no inhibition was noted in serum from an asthmatic with a positive skin response only to TSM.

CONCLUSION

Tetranychus urticae may be an important allergen in asthmatic non-farmers living around pear orchards and TSM extracts contain species-specific allergens as well as commonly shared allergens with house dust mite.