Latin name: Dermatophagoides microceras
Source material: Whole body culture
Common names: House dust mite, dust mite
See common geographical background to mites in our Scientific Documents (link to the right).
The House dust mite species Dermatophagoides microceras was first found in 1966 and first described in 1971 (1). Its distribution in the Scandinavian countries has been studied extensively (2). The mite has been identified in house dust in Great Britain, Scandinavia, the Netherlands, Spain and the United States, but the distribution of D. microceras in the rest of the world has not been well explored. The Dermatophagoides species are very similar but have differences in some physical characteristics: for example, in the male ventral posterior idiosoma and the aedeagus, and in the female genital opening and bursa copulatrix. The morphologically most conspicuous difference in the 3
Dermatophagoides species is that there are no 4 long train hairs on the abdomen end.
See common environmental background to mites in in our Scientific Documents (link to the right).
Mites are complex organisms, which produce thousands of different proteins and other macromolecules. Mite extracts are made from an aqueous extraction of a variable mixture of whole mites, nymphs, faecal pellets, eggs and spent culture media. Mite extracts contain over 30 different proteins, which can induce IgE antibody production in patients allergic to mite. Out of the 19 denominated allergens, major IgE binding has been reported for the Group 1, 2, 3, 9, 11, 14 and 15 allergens. The highmolecular- weight Group 11, 14 and 15 allergens have recently been described. The Group 1 and 2 allergens represent dominant specificities, which can account for much of the allergenicity of extracts (3). Data on storage mites could be extrapolated from House dust mites.
In a study using body and faecal extracts of D. pteronyssinus, D. farinae, D. microceras, Euroglyphus maynei and Gymnoglyphus longior, 21 of 29 protein bands, bound by sera from a mite-sensitive population and from the international reference pool of sera, were common to all 5 species of mite. All sera were unique with respect to proteins bound and species recognised. Mite proteins bound by more than 40% of sera included the Group 2 and 3 main allergens and 40.4 kDa and 27.8 kDa protein bands, all of which were found in every mite species studied. Similar response profiles among mite species suggest that human-specific IgE may bind predominantly to cross-reactive determinants on mite allergens (4).
Although approximately 20 allergens have been identified in the close family member D. pteronyssinus, to date only 1 allergen has been identified in D. microceras:
Der m 1, a Group 1 mite allergen, a major allergen (5-7).
Allergens from mites have both common and species-specific determinants. In this case, allergenic determinants are shared with other mites belonging to the Pyroglyphidae family and are highly cross-reactive with other Dermatophagoides spp. (4,8). Some mite allergenic proteins such as tropomyosin are widely cross-reactive among invertebrates such as Shrimp, Snails, Cockroaches and chironomids (9-10).
In a study investigating the individual allergens responsible for the cross-reactivity between D. siboney and other mite allergens in mite-allergic patients, inhibition studies had more positive results with D. farinae (86%), D. pteronyssinus (54%) and D. microceras (49%) extracts than with Lepidoglyphus destructor (20%), Tyrophagus putrescentiae (11%), Acarus siro (18%) and Blomia tropicalis (6%). A diverse pattern for the individual allergens was demonstrated. The N-terminal sequences of Der s 1, 2 and 3 allergens showed higher homology to D. farinae, D. pteronyssinus and D. microceras allergens. The homology of the Group 2 allergens was higher than that of the Group 1 allergens. The individual allergens of D. siboney were more similar to D. farinae and D. microceras than to D. pteronyssinus (6).
Unlike D. pteronyssinus and D. farinae, which appear in studies to be significant allergens in most geographic regions, the prevalence of D. microceras may vary widely. On one end of the spectrum, in a study of the homes of 111 asthmatic children in 3 climatic regions in Sweden, the major allergen Der m 1, together with Der p 1 from D. pteronyssinus and Der f 1 from D. farinae, was analysed. Der f 1 was the predominant House dust mite allergen, Der p 1 was the least often found, and Der m 1 represented 31% of the allergen load. However, in the Linkoping area, Der m 1 was the major House dust mite allergen (58%). Of the children with IgE antibodies against House dust mite, 67% reacted to all 3 mites. Mite sensitisation rates were marginally increased (7%) by the addition of IgE analysis of D. microceras to the routine analysis of IgE antibodies against D. pteronyssinus and D. farinae. The authors concluded that Der m 1 may be an important House dust mite allergen and should be considered when House dust mite exposure data are assessed in areas with a climate like that of Sweden (11).
However, in another Scandinavian population, in Denmark, a study found that both immunochemically and microscopically, D. farinae was dominant, D. pteronyssinus less frequent but important, and D. microceras insignificant (12).
In a study examining the specific allergen content of dust samples from the homes of 106 allergy clinic patients in Baltimore in the US, Dust mite allergen was detected in 99% of homes. D. farinae was found in 95%, D. pteronyssinus in 88% and D. microceras in 31%. Although sensitisation to these allergens was not evaluated, the study indicates that D. microceras may be an important allergen in this geographical region (13).
In a study of 579 asthmatic patients in Taiwan, it was shown through measuring IgE antibodies that almost 59% were sensitised to D. microceras, compared to 59.8% to D. pteronyssinus and 56.8% to D. farinae. Sensitisation to Cockroach was found in 38.3%, to Dog dander in 26.3%, to Candida albicans in 13.3%, to Cat dander in 10%, and to Cladosporium herbarum in 6.6%. The study indicates the importance of considering D. microceras when evaluating allergic individuals (14).
Among 93 Taiwanese asthmatic children aged from 3 to 15 years evaluated for sensitisation to 5 different species of mites, 63 were found to have IgE antibodies to at least 1 of the following mites: D. pteronyssinus, D. farinae, D. microceras, Euroglyphus maynei, and Blomia tropicalis. Sensitisation to D. pteronyssinus was found in 87%, to D. farinae in 85%, to D. microceras in 84%, to Euroglyphus maynei in 77%, and to Blomia tropicalis in 65% (15).
Similarly, in a Taiwanese study of 498 atopic children aged 2 to16 years, high prevalences of sensitisation were documented: 90.2%, to D. pteronyssinus, 88.2% to D. farinae, 79.5% to D. microceras, and 76.7% to Blomia tropicalis (16).
A group of 25 atopic children under 11 years of age in Oxford in the UK was studied for skin reactivity and IgE antibodies to 4 species of House dust mites: D. pteronyssinus, D. farinae, D. microceras and Euroglyphus maynei. All of the children were sensitised to D. pteronyssinus, and 80% of these children were also sensitised to D. farinae and D. microceras. Importantly, dust samples from various sites in the homes of the children revealed D. pteronyssinus in all the homes, but no D. farinae or D. microceras. A control group of 20 atopic children of similar ages who were not sensitised to House dust mite allergens had similar exposure to the 4 mite species. These results suggest that factors in addition to mite exposure are important in the development of allergen-specific IgE responses to House dust mites (17).
Systemic anaphylaxis can occur after the ingestion of heated or unheated mitecontaminated foods. This problem may be more prevalent in tropical and subtropical countries than previously recognised. The most common symptoms following the ingestion of mite-contaminated flour were breathlessness, angioedema, wheezing, and rhinorrhea, and these started between 10 and 240 minutes after eating (18).
Compiled by Dr Harris Steinman, firstname.lastname@example.org
- Griffiths DA, Cunnington AM. Dermatophagoides microceras sp.n.: a description and comparison with its sibling species D. farinae. J Stored Prod Res 1971;7:1
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- Warner A, Boström S, Munir AKM, Möller C, Schou C, Kjellman N-IM. Environmental assessment of Dermatophagoides mite-allergen levels in Sweden should include Der m 1. Allergy 1998;53(7):698-70
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