House dust mite

? House dust mite Conservation status: Secure
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Class: Arachnida Order: Acarina Family: Pyroglyphidae Genus: Dermatophagoides Species: D. pteronyssinus
Binomial name
Dermatophagoides pteronyssinus Trouessart, 1897

The house dust mite (Dermatophagoides pteronyssinus in Europe and Dermatophagoides farinae in North America), sometimes abbreviated by allergists to HDM, is a cosmopolitan guest in human habitation. They are considered to be one of the most common causes of asthma worldwide.

Contents 1 Description 2 Habitat 3 Asthma 4 External links and references 5 External links

Description

Both male and female adult house dust mites are globular in shape, creamy white and have a striated cuticle. The female measures approximately 420 micrometres in length and 320 micrometres in width. The male is approximately 420 micrometres long and 245 micrometres wide. A member of the phylum Arthropoda, post-larval stages of house dust mites have eight legs; larval stages have six legs.

The average life cycle for a male house dust mite is approximately 19-30 days while a mated female house dust mite can live for up to two months, laying eggs for the last 30 days of her life.

Habitat

The dust mite thrives in the modern environment of fully-carpeted, double-glazed, draft-proof homes, and is comfortable at 25 degrees Celsius (75-80 degrees Fahrenheit) and 75% relative humidity. Temperatures of over 60 degrees Celsius (140 degrees Fahrenheit) for a period of one hour are fatal to dust mites. The mites are particularly common in mattresses, carpets and bedding.

The house dust mites do not bite or sting. The mite generally lives on shed human skin cells, which are pre-digested by the fungus Aspergillus repens. An average person sheds about 1.5 grams of skin a day (approximately 0.3-0.45 kg per year), which is enough to feed roughly a million dust mites. Further, dust mites in bedding derive moisture from human breathing, perspiration, and saliva.

Asthma

The house dust mite is one of the most significant source of allergens, implicated in allergic asthma, rhinitis, conjunctivitis and dermatitis. One of the more important proteins responsible for the allergic reaction is DerP1, a protease digestive enzyme found in mite feces.

Measures to control house dust mites:

• Vacuuming carpeted areas regularly, preferably with a HEPA filter-equipped vacuum cleaner
• Regular damp dusting of surfaces
• Replacement of carpets with vinyl flooring
• Covering of mattresses and pillows with impervious materials
• Daytime internment of children's plush toys in a freezer
• Use of chemicals to kill mites (acaricides)
• Use of fungicides to kill Aspergillus
• Use an FDA approved air filtration & cleaning system (especially with high-efficiency particulate air (HEPA+ filtration))
• Reduce ambient humidty below 70% to inhibit growth of Aspergillus

Though these methods can help to reduce the level of house dust mites, attempts to eradicate homes completely have yet to be successful. Immunotherapy, in the form of injections of the allergen into patients, has been successful for some in much the same way that "allergy shots" have been helpful for sufferers of hayfever.

External links and references

• University of Nebraska "There are two species of house dust mites, belonging to the genus Dermatophagoides, that are found in North America. These mites are so tiny that they are virtually invisible without magnification. They pass through six developmental stages, and the adult form may also molt once. Adult female mites lay cream-colored elliptical eggs coated with a sticky fluid that helps them adhere to the substrate. Under optimal conditions, the cycle from egg to adult mite takes about one month."
• Ohio State University "House dust mites, due to their very small size (250 to 300 micrometres in length) and translucent bodies, are not visible to the unaided eye. For accurate identification, one needs at least 10X magnification. The adult mite's cuticle (covering) has simple striations that can be seen from both the dorsal (top) view and from the ventral (bottom) view. The ventral view of the house dust mite reveals long setae (hairs) extending from the outer margins of the body and shorter setae on the rest of the body. Through the microscope, one will see many oval-shaped mites scuttling around and over one another. There are eight hairy legs, no eyes, no antennae, a mouthpart group in front of the body (resembles head) and a tough, translucent shell, giving a fearsome appearance."
• University of Florida "The term "house dust mites" has been applied to a large number of mites found in association with dust in dwellings. The American house dust mite, Dermatophagoides farinae Hughes, and the European house dust mite, Dermatophagoides pteronyssinus (Trouessart), are discussed here. The first permanent structures for houses date back to 6,000 to 5,000 B.C., but it was not until the late 1600s that scientist became interested in the dust of houses. The pyroglyphids are parasites associated with birds and/or mammals. Kern (1921) found house dust to give positive cutaneous reactions in sensitive patients. Cook (1922) and Coa (1922) also found that dust extracts gave positive skin reactions in over 30 per cent of the individuals tested. Voorhorst et al. (1964) and Oshima (1964) first published their accounts that mites were recognized to contribute to the house dust allergy problem."

The content of this page is retrieved from http://en.wikipedia.org/wiki/House_dust_mite under GFDL