House dust mites (HDM, or simply dust mites) are a large number of mites found in association with dust in dwellings.
The main species are identified as:
- Dermatophagoides microceras
- Dermatophagoides pteronyssinus (European house dust mite)
- Euroglyphus maynei (Mayne's house dust mite)
Biology
Taxonomy
The dust mites are cosmopolitan pyroglyphids.
Characteristics
House dust mites, due to their very small size and translucent bodies, are barely visible to the unaided eye. A typical house dust mite measures 0.2â€"0.3 millimetres (0.008â€"0.012 in) in length. For accurate identification, one needs at least 10× magnification. The body of the house dust mite has a striated cuticle.
Diet
They feed on skin flakes from humans, and animals, and on some mold. Dermatophagoides farinae fungal food choices in 16 tested species commonly found in homes was observed in vitro to be Alternaria alternata, Cladosporium sphaerospermum, and Wallemia sebi, and they disliked Penicillium chrysogenum, Aspergillus versicolor, and Stachybotrys chartarum.
Predators
The predators of dust mites are other allergenic mites (Cheyletus), Silverfish and pseudoscorpions.
Reproduction
The average life cycle for a male house dust mite is 10â€"19 days. A mated female house dust mite can last up to 70 days, laying 60 to 100 eggs in the last 5 weeks of her life. In a 10-week life span, a house dust mite will produce approximately 2,000 fecal particles and an even larger number of partially digested enzyme-covered dust particles.
Health issues
Allergies
House dust mite allergy
The mite's gut contains potent digestive enzymes (notably Peptidase 1) that persist in their feces and are major inducers of allergic reactions such as wheezing. The mite's exoskeleton can also contribute to allergic reactions. Unlike scabies mites or skin follicle mites, house dust mites do not burrow under the skin and are not parasitic.
Severe dust mite infestation in the home has been linked to atopic dermatitis and epidermal barrier damage has been documented.
House dust mites are associated with allergic rhinitis and asthma. Efforts to remove these mites from the environment have not been found to be effective. Immunotherapy may be useful in those affected. Subcutaneous injections have better evidence than under the tongue dosing. Topical steroids as nasal spray or inhalation may be used.
Oral mite anaphylaxis
Dermatophagoides spp. can cause oral mite anaphylaxis (aka pancake syndrome) when found in flour.
Dust mite control techniques
Bed linen
Weekly changing the bed linen reduces the risk of exposure to dust mites.
Cotton covers not covered with complete mattress covers are very likely to become colonised by bacteria and molds; they must be cleaned periodically (at least every 2nd-3d month).
Dust mite eggs are freeze tolerant (-70°C for 30 minutes); hatching can normally be prevented by exposure of fabrics to:
- Direct sunlight for 3 h or
- Dry/wet heat of 60 and 70°C for a minimum of 30 min.
- Dust mites drown in water.
Dust mite-proof bedclothes may reduce the exposure to 20%.
Good properties of anti-mite fabrics have been identified as being:
- Thread count greater than 246.
- Pore size of between 2-10 micron.
- Allergen impenetrability >99%.
- Dust leakage of less than 4%.
- Breathability between 2-6 cm3/second/cm2.
Indoor climate
A practical way to control dust mites and their allergens is to maintain a relative humidity of less than 45% with a dehumidifier during summer, and a room temperature of 22°C.
References
External links
- House dust mites on the University of Florida / Institute of Food and Agricultural Sciences Featured Creatures website
- Dust Mite Allergy on the Asthma and Allergy Foundation of America website
