Mites

Print Tell a friend

Booklet: Mites.
Allergy - Which allergens? Phadia AB, 2007.

Mites comprise a huge and various group of tiny arthropods in the class Arachnida, which they share with scorpions and spiders, and in the subphylum Chelicerata, which they share with ticks. But while some mites are visible to the naked eye, like ticks, others are microscopic; and while some mites are parasitic like ticks, most are not. Mites have 8 legs instead of 6 (except in the nymph stage), differentiating them from insects. Their bodies are plump, sparsely haired, oval and not in themselves articulated. The mandibles and feelers resemble tongs.

As a very ancient organism, the mite is enormously diversified and adapted to a wide variety of environments, including plants, animals, humans, soil, fresh and salt water, organic rubbles, houses, mattresses, and old books. There are free-living, saprophitic, parasitic and predator mites.

Mites are important in soil and forest ecology and agriculture. Depending on the species and the circumstances, they can be either economically destructive pests (especially in food stores) or essential to the balance of biological systems; and either harmless to health, or direct or indirect causes of diseases in humans and animals. Among the disease-causing mites that usually act non-allergenically are the Itch or Scabies mite Sarcoptes scabiei hominis and the Straw itch mite Pyemotes tritici (1). Some mites whose environment is stored food may affect foodstuff workers, causing characteristic dermatitis: they can act either directly, by stings and bites, or indirectly, provoking an allergic hypersensitivity (2).

Certain species of microscopic mites occupy an insidious place among allergens. Not only, like pollens, are they invisible and from very common environmental sources, forming ambient mediators of allergic disease, but their sources are not even as distinct as certain widespread species of trees. These mites are instead basically part of the atmosphere of human civilisation. They prevail in domestic settings, agriculture and certain industries - especially domestic settings, where most people spend most of their time.

But a great number of factors play a role in exposure to these mites. The prevalence of different categories of mites may vary considerably among geographical locations (3). Different socioeconomic conditions influence the prevalence of domestic mites. For example, in Salvador, a Brazilian city, the mite Dermatophagoides pteronyssinus was found more frequently in the beds of the wealthy than of the poor (4) Mite allergens may spread where mites do not. Public transport vehicles and schools can be sources of mite allergens (5-7). The allergens accumulate on the skin and hair of dogs (8).

Humans themselves can be carriers as well as victims of allergenic mites. Among 1,994 individuals with different occupations, 8.07% were shown to carry mites in their urine and/or stool. The species of mites in the samples were consistent with those found in the individuals’ working environments. A significant association was found between mite infection and occupation, in particular among those working in medicinal herb storehouses and rice storehouses and mills; and in miners, railway workers, pupils and teachers (9).

There are 3 basic kinds of well recognised allergenic mites: House dust mites, Storage mites, and Plant mites—among these latter are the Red spider mite and Citrus mites. (It should be kept in mind, however, that these 3 major types are not the only causes of mite allergy; Hemisarcoptes cooremani, for example, which preys on scale insects, can cause allergic reactions (10).

The most important allergy-causing mites worldwide are the House dust mites Dermatophagoides farinae, D. pteronyssinus, Euroglyphus maynei, and the Storage mite Blomia tropicalis, which because of its common presence in house dust is now recognised as a domestic mite. Most mite infestations involve multiple species, but proportions differ among geographical regions (11), among buildings and even among areas within a building. Mites’ preference for high relative humidity keeps them abundant in moist climates and in homes, and scarce in desert climates, public buildings and transportation facilities (12).

House dust mites, belonging to the Pyroglyphidae family, live mainly in households, where they eat the human skin cells which are the chief component of house dust. Their numbers have apparently grown enormously because of the now much better enclosed and heated houses of the Northern Hemisphere, and because of the trend worldwide toward Western furnishings: window curtains, upholstery, mattresses, pillows, and carpeting, all of which tend to be thick and layered, providing superb havens for House dust mites (13), and which are difficult to clean, adding to the challenges that the physical properties of House dust mites themselves create for cleaning (see below).

The main species of Storage mites are Glycophagus domesticus, Lepidoglyphus destructor, Blomia kulagini and Blomia tropicalis. Blomia tropicalis predominates in subtropical and tropical areas. Since the primary habitat of Storage mites is the grains and cereals they eat, they are most common on farms, in granaries and in factories. "The walking dust" consists of millions of mites moving on barn or stable surfaces. Such dust is naturally a potent trigger of occupational allergy. (Interestingly, though, Storage mite is not homogenously present in grains and cereals. In a flat storage facility for wheat, most mites were found in the upper 0.5 m of the bulk (14). Exposure to these mites has been increasingly recognised as a cause of asthma and rhinitis. And according to recent evidence, some Storage mites have penetrated into the habitats of House dust mites. Studies from several countries have shown that IgE mediated allergy to Storage mites is of considerable importance in both rural and urban populations; sensitisation is not restricted to those with occupational exposure (15) Populations in damp urban housing would be at special risk (16). Moreover, these mites have been found even in dry regions, as reported after examination of house dust in Cairo, Egypt, for example (17).

Some of the same allergens are produced by both House dust and Storage mites; therefore, the allergic diseases they cause should be very similar (18-19). The allergens from different types and species of mites can, however, be quite different, and clinicians should consider non-cross-reactive allergens also as possible causes of reactions. The full range of possible environmental factors should always be kept in mind.

Exposure to Storage mite allergens can be by ingestion (20), which can cause devastating allergic reactions. Recently, anaphylaxis was reported. A 13-year-old boy experienced a sore throat and tight chest approximately a minute after eating homemade wheat flour hotcakes; this reaction was followed by a stuffy throat and paleness of the face. A 7-year-old girl experienced coughing, wheezing, streaming eyes and skin flushing an hour after eating homemade "tako-yaki". Fifteen months later, sneezing, coughing, wheezing, generalised pruritus, and streaming eyes occurred after she ate homemade buns. Both children had high levels of IgE antibodies to Dermatophagoides farinae. Mites were found in the boy’s hotcake. Three of 176 packages of wheat flour from local retail outlets and 7 of the 127 from homes were found to be infested with mites (21). Storage mites also endanger public health also because they produce transmit mycotoxin-producing fungi (22).

The third category, broadly known as Plant mites, is found on living plants in fields and orchards. One example is the Red spider mite, common on Tomatoes. Since the mites persist on the product after harvest and frequently survive until reaching the consumer, they can produce commonly misdiagnosed reactions. Even more common and more commonly confusing reactions are occupational. For example, a person having allergic reactions from work exposure to fresh Tomato naturally suspects only a Tomato allergy, and a clinician needs to confirm or refute this suspicion through testing and not simply rely on the report (23).

This is particularly true because Plant feeding mites are among the most important arthropods in greenhouses. The stable environmental conditions maintained in these buildings for optimal growth of plants, especially in the case of monoculture, also nurture mites. Sometimes mites are pests, causing economic damage to greenhouse crops, but they can also be useful and may be deliberately employed in the biological control of insects. Typical pest mites in greenhouses are the Spider mites (Tetranychus species) and Bulb mites (Rhizoglyphus species). Predatory mites used in biological control in greenhouses include Phytoseiid and Laelapid mites. A range of mite species can cause allergic reactions in greenhouse workers.

Mites are complex organisms, which produce thousands of different proteins and other macromolecules. Mite extracts for testing are made from an aqueous extraction of a variable mixture of whole mites, nymphs, faecal pellets, eggs and spent culture media. The extracts contain over 30 different proteins that can induce IgE antibody production in patients allergic to mite. Out of the 19 denominated groups of allergens, major IgE binding has been reported for the Group 1, 2, 3, 9, 11, 14 and 15 allergens. The high-molecular-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 (24). Data on Storage mites could be extrapolated from House dust mites, which have been the main focus of research.

Mite extracts contain a variety of biochemically active enzymes, including trypsin, chymotrypsin, carboxypeptidase A and B, glucoamylase and lysozyme. Marked differences in the relative concentrations of some of these enzymes, particularly trypsin and carboxypeptidase A, occur in different mite extracts (25-26). (A number of these enzymes are physicochemically similar to corresponding enzymes from vertebrate and invertebrate sources.) The age of the faeces could be important, or there could be a threshold where proteolytic activity becomes dominant. Low concentrations of allergens may occur for a variety of other reasons: allergens could be secreted proteins, and some of these (e.g., Der p 14) are unstable in aqueous extracts. Allergens in the mite are compartmentalised, so destruction by hydrolytic enzymes may occur; for example, haemolymph proteins, previously not mixed with a mite’s digestive enzymes, may be destroyed upon mixing.

Even when allergens are well preserved, mite extracts used for commercial testing may not mimic the native mite allergen environment in general at all accurately. All that can broadly be said about the concentrations of most allergens in the environment is that these are unknown but are probably sparse. For an accurate diagnosis and effective treatment of mite allergy, specimens should be collected and identified by trained specialists.

But once a diagnosis is made, it can be very difficult to remove House dust mites from a home or workplace. Allergenic mites are extremely well adapted for infecting households. Adults are about 300 μm in size. Some species have a stage, termed hypopial, that conveys resistance to adverse environmental influences. In any case, it is apparently not mainly mite bodies or body parts causing allergic reactions but the faeces and other excreted substances. These are especially potent allergens because of the various digestive enzymes they contain (27).

Cleaning is difficult first of all because the faeces are extremely tenacious. Special vacuum machines for breaking up the faeces may spew the material back into the home and make the problem worse: the tiny size of mite wastes, once they are broken up, makes them easily airborne. Ordinary cleaning and vacuuming may achieve little or nothing, or may merely bring mite material to the surface of soft furnishings. Some commercial aracides may be effective in killing mites, but could presumably produce substantive drops in allergen levels only in conjunction with stringent measures to remove the mite material that is the operative source of allergens. A study of various measures for removing mites had gloomy results, with only 4 out of 23 trials achieving a reduction in mite allergen levels (28).

However, since high indoor aeroallergen levels are an important risk factor for the development and exacerbation of allergic disease and asthma, efforts at environmental control are widely recommended (27). The obvious steps may be most effective. For many years, doctors have advised the parents of asthmatic children to rip up carpeting and use special mattress covers. Frequent washing of textiles in very hot water is also recommended. An old-fashioned remedy for respiratory disease is probably very sound: send the patient to the mountains. Some of the great spas of Europe are in the Alps, where the air is in fact more pure, and not just of industrial pollution: mite populations are far lower. (Installing dehumidifiers or air cleaners or filters in a home may produce some of the same benefits.) Damp, lowland areas, in contrast, harbour far more mites.

Storage and Citrus mites appear to cause only respiratory allergies in the majority of cases. House dust mites commonly worsen eczema and other skin conditions as well. In a study comparing sensitisation to House dust mite with sensitisation to Storage mite, the mean age for the onset of sensitisation was 6.7 years for House Dust mites and 18.7 years for Storage mites. Conjunctivitis was more frequent in patients allergic to Storage mites, whereas perioral syndrome (itching of the tongue and swelling of the lips) was seen only in patients sensitised to Tyrophagus putrescentiae. This study concluded that damp climatic and indoor conditions and human activity, but not urban or rural living environments, influenced the differential sensitisation to House Dust mites and Storage mites (29).

Particularly interesting is the question of mites as a primary allergic trigger and their role in the spread of allergy into populations where it was unknown a generation before. Competing with the hygiene hypothesis (which holds that overly sanitary conditions can compromise the immune system early in life) is a theory that mites entering thirdworld households along with mattresses and carpets lead to dramatic increases in allergic sensitisation. In many such communities, in fact, Western furnishings long precede modern sanitation, creating an ideal environment for mites (13).

Main Types of Allergenic Mites

Fig. 1. Adapted from: RD, Allergy to storage mites. Clin Exp Allergy 1994;24(7):636-40.

ImmunoCAP mite allergens available for IgE antibody testing

Potential cross-reactivity

The pyroglyphid mites are commonly referred to as House dust mites. Among the Storage mites, the Glycyphagidae and Acaridae families predominate, and the Tetranycidae family contains the Plant mites.

Potential cross-reactivity between mites varies from very low to very high the more closely the species are related. Common and species-specific allergens exist.

For example, a higher degree of cross reactivity occurs among the House dust mites, in particular among the Dermatophagoides species, and a moderate degree of cross-reactivity among these species and other House dust mites such as Euroglyphus maynei (30-32). Amino acid sequences of Eur m 1 and Eur m 2 were reported to have a 84 to 86% sequence identity with the corresponding allergens from Dermatophagoides pteronyssinus and Dermatophagoides farinae mites. This was reported to be the same as the degree of sequence identity found between D. pteronyssinus and D. farinae, despite Euroglyphus being a member of the Pyroglyphinae subfamily rather than the Dermatophagoidinae subfamily (33).

Co-sensitisation to Storage mites is a frequent finding in patients sensitised to Dermatophagoides pteronyssinus. However, there is only low immunological crossreactivity between Pyroglyphidae (House dust mites) and non-Pyroglyphidae mites (Storage mites) (34). This is in spite of antigenic and allergenic determinants being shared by Dermatophagoides species and Tyrophagus putrescentiae, and in spite of the fact that the 16 kDa group 2 allergen of Dermatophagoides is one of the most prevalent allergens of T. putrescentiae (35-37).

Storage mites and D. pteronyssinus possess their own unique allergen or allergens. Cross-reactivity among the Storage mites is more common. Lepidoglyphus destructor, Glycyphagus domesticus and Tyrophagus putrescentiae are allergenically more closely related to each other than to Acarus siro (38). Similarly, results of other studies have suggested that the major allergens of T. putrescentiae have a strong cross-reactivity with D. pteronyssinus extracts, but that D. pteronyssinus allergens have only partial cross reactivity with T. putrescentiae extracts (37,39). Similarly, extensive cross-reactivity was demonstrated among Gly d 2, Lep d 2, and Tyr p 2, but little cross-reactivity was found between these allergens and Der p 2 (40).

Spider mite extracts contain speciesspecific allergens as well as allergens commonly shared with House dust mite and Citrus red mite (41-42).

Although allergic reactions are not commonly reported to the human pathogenic mite Sarcoptes scabiei (Scabies), a degree of cross-reactivity with Dermatophagoides pteronyssinus may exist (43-44).

The reader is referred to individual mite allergen overviews for more details.

References:

1. Arlian LG. Arthropod allergens and human health. Annual Review of Entomology. 2002;47:395-433
2. Liguori G, Ceccarelli MT, Mellino M, Marinelli P. Recent experience with mites in stored products. [Italian] Ann Ig 1989;1(1-2):237-46
3. Bousquet PJ, Chinn S, Janson C, Kogevinas M, Burney P, Jarvis D; European Community Respiratory Health Survey I. Geographical variation in the prevalence of positive skin tests to environmental aeroallergens in the European Community Respiratory Health Survey I Allergy 2007;62(3):301-9
4. Baqueiro T, Carvalho FM, Rios CF, dos Santos NM, Alcantara-Neves NM; Medical Student Group. Dust mite species and allergen concentrations in beds of individuals belonging to different urban socioeconomic groups in Brazil. J Asthma 2006;43(2):101-5
5. Pereira FL, Silva DA, Sopelete MC, Sung SS, Taketomi EA. Mite and cat allergen exposure in Brazilian public transport vehicles. Ann Allergy Asthma Immunol 2004;93(2):179-84
6. Taketomi EA, Justino CM, Pereira FL, Segundo GR, Sopelete MC, Sung SJ, Silva DA. Taxis but not private cars are mite allergen reservoirs in Brazil. J Investig Allergol Clin Immunol 2006;16(1):34-36
7. Abramson SL, Turner-Henson A, Anderson L, Hemstreet MP, Bartholomew LK, Joseph CL, Tang S, Tyrrell S, Clark NM, Ownby D. Allergens in school settings: results of environmental assessments in 3 city school systems. J Sch Health 2006;76(6):246-9
8. Randall AJ, Hillier A, Cole LK, Kwochka KW, Needham G, Wassom DL. Quantitation of house dust mite allergens (Der f 1 and group 2) on the skin and hair of dogs. Am J Vet Res 2005; 66(1):143-149
9. Li CP, Cui YB, Wang J, Yang QG, Tian Y. Acaroid mite, intestinal and urinary acariasis. World J Gastroenterol 2003;9(4):874-7
10. Arlian LG, Morgan MS, Houck MA. Allergenicity of the mite Hemisarcoptes cooremani. Ann Allergy Asthma Immunol 1999;83(6 Pt 1):529-32
11. Macan J, Kanceljak B, Plavec D, Milkovic- Kraus S. Differences in mite fauna between the continental and Mediterranean climates of Croatia: microscopy and Dustscreen test findings. Allergy 2003;58(8):780-3
12. Arlian LG, Morgan MS, Neal JS. Dust Mite Allergens: Ecology and Distribution Curr Allergy Asthma Rep 2002;2:401-411
13. Steinman HA, Donson H, Kawalski M, Toerien A, Potter PC. Bronchial hyper-responsiveness and atopy in urban, peri-urban and rural South African children. Pediatr Allergy Immunol 2003;14(5):383-93
14. Athanassiou CG, Kavallieratos NG, Palyvos NE, Sciarretta A, Trematerra P. Spatiotemporal distribution of insects and mites in horizontally stored wheat. J Econ Entomol 2005;98(3):1058-69
15. Franz JT, Masuch G, Musken H, Bergmann KC. Mite fauna of German farms. Allergy 1997;52(12):1233-7
16. van Hage-Hamsten M, Johansson E. Clinical and immunologic aspects of storage mite allergy. Allergy 1998;53(48 Suppl):49-53
17. Koraiem MK, Fahmy IA. Studies on house dust mites in Great Cairo, Egypt. J Egypt Soc Parasitol 1999;29(1):131-8
18. Olsson S. & Hage-Hamsten M. Allergens from house dust and storage mites: similarities and differences, with emphasis on the storage mite Lepidoglyphus destructor. Clin Exp Allergy 2000;30:912-919
19. Kanceljak-Macan B, Macan J, Buneta L, Milkovic-Kraus S. Sensitization to nonpyroglyphid mites in urban population of Croatia. Croat Med J. 2000;41(1):54-7
20. Hage-Hamsten M & Johansson SGO. Storage mites. Exp Appl Acarol 1992;16:117-128
21. Matsumoto T, Satoh A. The occurrence of mite-containing wheat flour. Pediatr Allergy Immunol 2004;15(5):469-71
22. Hubert J, Doleckova-Maresova L, Hyblova J, Kudlikova I, Stejskal V, Mares M. In vitro and in vivo inhibition of alpha-amylases of storedproduct mite Acarus siro. Exp Appl Acarol 2005;35(4):281-91
23. Steinman HA, Lee S. Concomitant clinical sensitivity (CCS) and Crossreactivity. Allergy & Clinical Immunology International 2003;15(1):18-29
24. Thomas WR, Smith WA, Hales BJ, Mills KL, O’Brien RM. Characterization and immunobiology of house dust mite allergens. Int Arch Allergy Immunol 2002;129(1):1-18
25. Stewart GA, Bird CH, Krska KD, Colloff MJ, Thompson PJ. A comparative study of allergenic and potentially allergenic enzymes from Dermatophagoides pteronyssinus, D. farinae and Euroglyphus maynei. Exp Appl Acarol 1992;16(1-2):165-80
26. Stewart GA, Kollinger MR, King CM, Thompson PJ. A comparative study of three serine proteases from Dermatophagoides pteronyssinus and D. farinae. Allergy 1994;49(7):553-60
27. Summarised in Fernandez-Caldas E, Puerta L, Caraballo L, Lockey RF. Mite allergens. Clin Allergy Immunol 2004;18:251-70
28. Custovic A, Murray CS, Gore RB, Woodcock A. Controlling indoor allergens. Ann Allergy Asthma Immunol 2002;88(5):432-41
29. Boquete M, Carballada F, Armisen M, Nieto A, Martin S, Polo F, Carreira J. Factors influencing the clinical picture and the differential sensitization to house dust mites and storage mites. J Investig Allergol Clin Immunol 2000;10(4):229-34
30. Arlian LG, Rapp CM, Fernandez-Caldas E. Allergenicity of Euroglyphus maynei and its cross-reactivity with Dermatophagoides species. J Allergy Clin Immunol 1993;91(5):1051-8
31. Arruda LK, Chapman MD. A review of recent immunochemical studies of Blomia tropicalis and Euroglyphus maynei allergens. Exp Appl Acarol 1992;16(1-2):129-40
32. Kemp SF, Lockey RF, Fernandez-Caldas E, Arlian LG. Skin test and crossreactivity studies with Euroglyphus maynei and Dermatophagoides pteronyssinus. Clin Exp Allergy 1997;27(8):893-7
33. Smith W, Mills K, Hazell L, Hart B, Thomas W. Molecular analysis of the group 1 and 2 allergens from the house dust mite, Euroglyphus maynei. Int Arch Allergy Immunol 1999;118(1):15-22
34. Garcia-Robaina JC, Eraso E, De la Torre F, Guisantes J, Martinez A, Palacios R, Martinez J. Extracts from various mite species contain cross-reactive and noncross-reactive IgE epitopes. A RAST inhibition study. J Investig Allergol Clin Immunol 1998;8(5):285-9
35. Arlian LG, Geis DP, Vyszenski-Moher DL, Bernstein IL, Gallagher JS. Antigenic and allergenic properties of the storage mite Tyrophagus putrescentiae. J Allergy Clin Immunol 1984;74(2):166-71
36. Park JW, Ko SH, Yong TS, Ree HI, Jeoung BJ, Hong CS. Cross-reactivity of Tyrophagus putrescentiae with Dermatophagoides farinae and Dermatophagoides pteronyssinus in urban areas. Ann Allergy Asthma Immunol 1999;83(6 Pt 1):533-9
37. Tee RD, Gordon DJ, van Hage-Hamsten M, Gordon S, Nunn AJ, Johansson SG, Taylor AJ. Comparison of allergic responses to dust mites in U.K. bakery workers and Swedish farmers. Clin Exp Allergy 1992;22(2):233-9
38. van Hage-Hamsten M, Johansson SG, Johansson E, Wiren A. Lack of allergenic cross-reactivity between storage mites and Dermatophagoides pteronyssinus. Clin Allergy 1987;17(1):23-31
39. Munhbayarlah S, Park JW, Ko SH, Ree HI, Hong CS. Identification of Tyrophagus putrescentiae allergens and evaluation of cross-reactivity with Dermatophagoides pteronyssinus. Yonsei Med J 1998;39(2):109-15
40. Gafvelin G, Johansson E, Lundin A, Smith AM, Chapman MD, Benjamin DC, Derewenda U, van Hage-Hamsten M. Cross-reactivity studies of a new group 2 allergen from the dust mite Glycyphagus domesticus, Gly d 2, and group 2 allergens from Dermatophagoides pteronyssinus, Lepidoglyphus destructor, and Tyrophagus putrescentiae with recombinant allergens. Allergy Clin Immunol 2001;107(3):511-8
41. Jee YK, Park HS, Kim HY, Park JS, Lee KY, et al. Two-spotted spider mite (Tetranychus urticae): an important allergen in asthmatic non-farmers symtomatic in summer and fall months. Ann Allergy Asthma Immunol 2000;84(5):543-8
42. Park HS, Jee YK, Kim YK, Lee SK, Lee MH, Kim YY. Identification of immunoglobulin E binding components of the two-spotted spider mite Tetranychus urticae: allergenic relationships with the citrus red mite and house-dust mite. Allergy Asthma Proc 2002;23(3):199-204
43. Falk ES, Bolle R. IgE antibodies to house dust mite in patients with scabies. Br J Dermatol 1980;103(3):283-8.
44. Moustafa EH, el-Kadi MA, al-Zeftawy AH, Singer HM, Khalil KA. The relation between scabies and hypersensitivity to antigens of house dust mites and storage mites. J Egypt Soc Parasitol 1998;28(3):777-87
    

• References