Wikipedia:Version 1.0 Editorial Team/Kentucky articles by quality and Demodex: Difference between pages
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{{Taxobox
| color = pink
| name = ''Demodex''
| image = Haarbalgmilbe.jpg
| regnum = [[Animal]]ia
| phylum = [[Arthropod]]a
| classis = [[Arachnid]]a
| subclassis = [[Acarina]]
| ordo = [[Trombidiformes]]
| familia = [[Demodicidae]]
| genus = '''''Demodex'''''
| subdivision_ranks = Species
| subdivision =
''[[Demodex brevis]]''<br>
''[[Demodex bovis]]''<br>
''[[Demodex canis]]''<br>
''[[Demodex caprae]]''<br>
''[[Demodex cati]]''<br>
''[[Demodex equi]]''<br>
''[[Demodex folliculorum]]''<br>
''[[Demodex ovis]]''<br>
''[[Demodex phyloides]]''<br>
}}
'''''Demodex''''' is a [[genus (biology)|genus]] of tiny [[Parasite|parasitic]] [[mite]]s which live in or near [[hair follicles]] of [[mammal]]s. About 65 species of Demodex mites are known; they are among the smallest of [[arthropod]]s. Two species living on [[human]]s have been identified: ''Demodex folliculorum'' and ''Demodex brevis'', both frequently referred to as an '''eyelash mites'''. ''Demodex canis'' lives on the domestic [[dog]]. Infestation with ''Demodex'' mites is common and usually does not cause any symptoms; occasionally some skin diseases can be caused by the mites.
==''Demodex folliculorum'' and ''Demodex brevis''==
''Demodex folliculorum'' and ''Demodex brevis'' are the only ''Demodex'' mites that have been found on humans. ''D. folliculorum'' was first described in 1842 by Simon; ''D. brevis'' was identified as separate in 1963 by Akbulatova. ''D. folliculorum'' is found in hair follicles, while ''D. brevis'' lives in [[sebaceous gland]]s connected to hair follicles. Both species are primarily found in the face, near the nose, the [[eyelash]]es and [[eyebrow]]s, but also occur elsewhere on the body.
The adult mites are only between [[1 E-4 m|0.3 mm and 0.4 mm]] long, with ''D. brevis'' slighly shorter than ''D. folliculorum''.<ref name=rufli>Rufli T, Mumcuoglu Y. "The hair follicle mites ''Demodex folliculorum'' and ''Demodex brevis'': biology and medical importance. A review." ''Dermatologica.'' 1981;162(1):1-11. PMID 6453029</ref> They have a semi-transparent elongated body that consists of two fused segments. Eight short segmented legs are attached to the first body segment. The body is covered with scales for anchoring itself in the hair follicle, and the mite has pin-like mouth-parts for eating [[skin|skin-cells]], [[hormone]]s and oils ([[sebum]]) which accumulate in the hair follicles. The mite's [[digestive system]] is so efficient and results in so little waste that there is no excretory orifice. The mites can leave the hair follicles and slowly walk around on the skin, at a speed of about 8–16 cm/hour, especially at night; they try to avoid light.<ref name=rufli/>
Female ''Demodex folliculorum'' are somewhat shorter and rounder than males. The total lifespan of a Demodex mite is several weeks. Both male and female Demodex mites have a genital opening, and fertilization is internal.<ref>Rush, A. 2000. "[http://animaldiversity.ummz.umich.edu/site/accounts/information/Demodex_folliculorum.html ''Demodex folliculorum'']", Animal Diversity Web. Accessed January 07, 2007.</ref>
Mating takes place in the follicle opening, and eggs are laid inside the hair follicles or sebaceous glands. The six-legged [[larva]]e hatch after 3-4 days, and it takes about seven days for the larvae to develop into adults. The dead mites decompose inside the hair follicles or sebaceous glands.
Older people are much more likely to carry the mites; estimates range as high as an 96-98% infestation rate in aged people. The lower rate of children may be due to the fact that children produce much less sebum. It is quite easy to look for one's own demodex mites, by carefully removing an eyelash or eyebrow hair and placing it under a [[microscope]].
The mites are transferred between hosts through contact of hair, eyebrows and of the sebaceous glands on the nose. Different species of animals host different species of demodex; and demodex is not contagious between different species.
In the vast majority of cases, the mites go unobserved, without any adverse symptoms, but in certain cases (usually related to a suppressed [[immune system]], caused by stress or illness) mite populations can dramatically increase, resulting in a condition known as [[demodicosis]], characterised by itching, inflammation and other skin disorders. [[Blepharitis]] (inflammation of the eyelids) can also be caused by Demodex mites.
[[Image:Demodex mite 1.JPG|thumb|left|''Demodex canis'']]
There is some evidence linking demodex mites to some forms of the skin disease [[rosacea]], possibly due to the bacterium ''[[Bacillus oleronius]]'' found in the mites.<ref> [http://www.rosacea.org/press/archive/20040503.php New Study Shows Role for Bacteria in Development of Rosacea Symptoms], National Rosacea Society press release, 3 May 2004
</ref> Some people believe that there is also a link to [[acne vulgaris]], but there is little research to back this up, and quite reasonable experimental evidence linking acne vulgaris to a sensitivity to ''[[Propionibacterium acnes]]''.
==''Demodex canis''==
The species ''Demodex canis'' lives only on the domestic [[dog]]. While, like with humans, most dogs live with their mites without harm, a minority do not have immune systems capable of completely controlling the mites, leading to a potentially dangerous infestation called [[Mange|demodectic mange]]. While direct treatment for severe cases is possible using a drug known as [[Mitaban]] which is applied to the skin, improved nutrition and checking for other, immune-system suppressing diseases are also recommended.
==References==
<references/>
==External links==
* [http://www.microscopy-uk.org.uk/mag/artmay00/demodex.html ''Demodex, an inhabitant of human hair follicles, and a mite which we live with in harmony''], by M. Halit Umar, published in the May 2000 edition of Micscape Magazine, includes several micrographs
* [http://www.worsleyschool.net/science/files/eyelash/creatures.html Description and pictures]
* [http://www.emedicine.com/oph/topic517.htm Demodicosis], an article by Manolette R Roque, MD
* [http://www.findarticles.com/p/articles/mi_m1272/is_2705_132/ai_113302303 ''Mites might cause mighty problems'', USA Today (Magazine), Feb 2004]
* [http://www.thepetcenter.com/exa/dem.html ''Demodex in the Dog'', by T. J. Dunn, Jr. DVM]
* [http://www.demodexmites.org ''Demodex Mites information'', by Neil Ramos]
[[Category:Acari]]
[[de:Haarbalgmilbe]]
[[it:Demodex]]
[[ja:ニキビダニ]]
[[no:Hårsekkmidder]]
[[pl:Nużeńce]]
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