House dust mite
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| House dust mite | ||||||||||||||||
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 Dermatophagoides pteronyssinus
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Secure
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| Binomial name | ||||||||||||||||
| Dermatophagoides pteronyssinus Trouessart, 1897 |
The house dust mite (sometimes referred to by allergists as HDM), is a cosmopolitan guest in human habitation. Dust mites feed on organic detritus such as flakes of shed human skin and flourish in the stable environment of dwellings. House dust mites are a common cause of asthma and allergic symptoms worldwide. Some of the gut enzymes (notably proteases) produced by the house mite persist in their fecal matter, and can be strongly allergenic. The European house dust mite (Dermatophagoides pteronyssinus) and the American house dust mite (Dermatophagoides farinae) are two different species, but are not necessarily confined to Europe or North America; a third species Euroglyphus maynei also occurs widely.
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[edit] Size
The body of a house dust mite is just visible against a dark background in normal light. A typical house dust mite measures 420 micrometers in length and 250 to 320 micrometers in width. Both male and female adult house dust mites are creamy blue and have a rectangular shape. The body of the house dust mite also contains a striated cuticle. Like all acari, house dust mites have eight legs (except 3 pairs in the first instar). Dust mites can be transported in dust bunnies or airborne by minor air currents generated from normal household activities[verification needed].
[edit] Life cycle
The average life cycle for a male house dust mite is 10 to 19 days. A mated female house dust mite can live for 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 2000 fecal particles and an even larger number of partially digested enzyme-covered dust particles.[1]
A simple washing will remove most of the waste matter. Both being exposed to temperatures of over 60 degrees Celsius (140 degrees Fahrenheit) for a period of one hour, freezing, or exposure to temperatures below 20 °C (68 °F)[verification needed], will typically prove fatal to house dust mites; a relative humidity less than 50 may also be fatal.[2] Ten minutes in a household clothes dryer at lethal temperatures has been shown to be sufficient to kill all the dust mites in bedding.[3] House dust mites reproduce quickly enough that their effect on human health can be significant.
[edit] Habitat and food
The house dust mite survives in all climates, even at high altitude. A person sheds about 1.5 grams of skin cells and flakes every day (approximately 0.3–0.45 kg per year), which is enough to feed roughly a million house dust mites under ideal conditions.[verification needed] If trying to control house dust mites, humidity should be kept low. House dust mites thrive in the indoor environment provided by homes, specifically in bedrooms and kitchens. Dust mites survive well in mattresses, carpets, furniture and bedding, with figures around 188 animals/g dust. Even in dry climates, house dust mites survive and reproduce easily in bedding (especially in pillows), deriving moisture from the humidity generated by human breathing, perspiration, and saliva[verification needed].
House dust mites consume minute particles of organic matter. Like all acari, house dust mites have a simple gut; they have no stomach but rather diverticulae, which are sacs or pouches that divert out of hollow organs. Like many decomposer animals, they select food that has been pre-decomposed by fungi. House dust mites eat the same particle several times, only partially digesting it each time; between feedings, house dust mites leave particles to decompose further. Only when the particles are fully digested do they enter the dust mite's fecal matter.[verification needed]
[edit] Asthma and allergies
Allergens produced by house dust mites are among the most common triggers of asthma. A safety and tolerability clinical trial (Phase IIa) has been completed with positive results by Cytos Biotechnology using an immunotherapeutic (CYT003-QbG10) for treatment of house dust mite-triggered allergies.[4]
Some main signs of house dust mite allergies are itchiness, sneezing, inflamed or infected eczema, watering/reddening eyes, runny nose and clogging in the lungs.
Most people who have dust mite allergy sneeze when they wake up in the morning. They will generally feel better as they go out of their rooms, then at night when they sleep, the cycle repeats over again. This can cause the allergy to be chronic and long lasting. To determine the concentration of dustmites the Acarex Test is performed.
[edit] Myths and misconceptions
It is commonly believed that the accumulated detritus from dust mites can add significantly to the weight of mattresses and pillows. While it is true that the fecal matter of dust mites will increase over time, there is no scientific evidence for these claims.[5]
Allergy and asthma sufferers are also often advised to avoid feather pillows due to the presumed increased presence of the house dust mite allergen (Der p I). The reverse, however, is true. A 1996 study from the British Medical Journal has shown that polyester fibre pillows contained more than 8 times the total weight of Der p I and 3.57 times more micrograms of Der p I per gram of fine dust than feather pillows.[6]
[edit] Eradication
Boron powder is often used to eradicate house dust mites.[7]
[edit] References
- ^ http://www.pneumologiamo.it/allergia_acari.htm
- ^ "Hotter is better for removing allergens in laundry". American Thoracic Society. May 20, 2007. http://www.eurekalert.org/pub_releases/2007-05/ats-hib051407.php.
- ^ Miller JD, Miller A. Ten minutes in a clothes dryer kills all mites in blankets (abstract). J Allergy Clin Immunol 1996;97:423.
- ^ Staff (2007-06-15). "Clinical Trials Update: Allergies" (print). Genetic Engineering & Biotechnology News (Mary Ann Liebert, Inc.): p. 52.
- ^ Adams, Cecil (April 7, 2000). "Does a mattress double its weight due to dust mites and their debris?". The Straight Dope. http://www.straightdope.com/columns/read/2545/does-a-mattress-double-its-weight-due-to-dust-mites-and-their-debris. Retrieved on 2008-09-19.
- ^ Kemp, TJ (October 12 1996). "House dust mite allergen in pillows" (in English). British Medical Journal (united Kingdom: British Medical Association) 313 (7062): 916–919. "For many years asthmatic patients have been told to avoid using feather filled pillows on their beds, although there is no evidence to support this practice. Strachan and Carey's case-control study is the first to have directly challenged this assumption.1 This study showed that, after exclusion of asthmatic subjects whose bedding had been changed because of their disease, pillows with synthetic fillings were a risk factor for severe asthma. In the light of this finding, we have compared pillows with synthetic and feather fillings for their content of Der p I, the major allergen of the house dust mite Dermatophagoides pteronyssinus.".
- ^ Codina, R.; RF Lockley, R Diwadkar, LL Mobly, S Godfrey (2003). "Disodium octaborate tetrahydrate (DOT) application and vacuum cleaning, a combined strategy to control house dust mites". Allergy. http://www.dustmitex.com/Allergy_DOT_Study.pdf. Retrieved on 2009-05-27.
[edit] External links
- Dust Mite Information - Allergies, biology, control measures and locating dust mites
- house dust mites on the UF / IFAS Featured Creatures Web site
