Demodex folliculorum

Demodex folliculorum
Demodex folliculorum
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Trombidiformes
Family: Demodicidae
Genus: Demodex
Species: D. folliculorum[1]
Binomial name
Demodex folliculorum
Simon, 1842

Demodex folliculorum is a species of face mite. D. folliculorum is one of the parasitic face mites that occur on people (other than Demodex brevis).[1][2] Demodex derives from the Greek roots, demos- fat, and dex- worm.[3] When large numbers of D. folliculorum are found on humans, the infestation is known as "demodicosis".[4]

Contents

History

Demodex was first discovered in 1840 in dogs to cause mange, any skin disease caused by parasitic mites affecting animals. Tulk was the first to publish about Demodex in dogs. In 1842, a Frenchman name Berger discovered Demodex folliculorum in earwax. Demodex folliculorum was first discovered in human hair by a researcher at Nioxin, a major hair care and cosmetics manufacturer with a high powered, newly developed, hand-held microscope that was capable of magnifying the human scalp up to 1000 times. This magnification of the human scale allowed them to see the dozens of mites deep inside the hair follicles. The mites were found "eating" off the oil secretions of the scalp known as sebum. Nioxin Research Laboratories worked with Tulane University, and found that 88% of people with thin hair have Demodex folliculorum. On the other hand, only 9% of individuals with normal hair density had Demodex folliculorum.[5]

Parasitic behavior

These parasites are found in the human hair follicles, normally found in greater numbers around the cheeks, nose, eyebrows, eyelashes, and forehead. They could also be found in other parts of the body such as arms, chest, and ears. It is a species of tiny mites that have been thought to contribute to hair loss (though this hypothesis is under debate) [6] and live in our pores and hair follicles. The mites vary in size from 0.1mm to 0.4mm long.[5] Their food is mainly sebaceous secretions and dead cells, such as cytoplasm.[2] They do not defecate on the skin; however, they do reproduce on it.[2] Mites do not invade internal organs.

Morphology

D. folliculorum is semi-transparent elongated organism consisting of a head, neck, body, and tail.[4] D. folliculorum is worm-like, with tiny claws, and scales over their entire body, which allows it to anchor itself in the hair follicles. As an adult, D. folliculorum can measure 0.1 mm to 0.4 mm in length and possess four pairs of short legs near its head and neck region.[4] However as a larvae and/or nymph, D. folliculorum resembles the adult but has three pairs of short legs near its head and neck region.[4] The body and tail region of D. folliculorum is striated.[4]

Demodex folliculorum v. Demodex brevis

Both Demodex folliculorum and Demodex brevis are typically found on the human face.[7] Demodex folliculorum resides in hair follicles, whereas Demodex brevis survives in sebaceous glands adjacent to hair follicles. For instance, around the eye area, Demodex folliculorum is found in the follicles of the eyelashes. In contrast, Demodex brevis inhabits the sebaceous gland of the eyelashes and the meibomian glands. Demodex brevis was first identified separate from Demodex folliculorum in 1963 by Akbulatova.

Life cycle

The entire life cycle of D. folliculorum takes places in the time span of 18–24 days on its host.[4] Females have a ventral vulva anus opening, and males have a well-developed penis located between the first and second legs. A female adult lays 20-24 eggs in a single hair follicle, as they grow they become tightly packed, and develops into larvae.[4] During the day, they remain feeding within the follicle. Later at night, they emerge onto the surface of the mate and eggs are laid into the hair follicles. The larva is then washed by a sebaceous flow, produced by the host’s sebaceous glands, into the mouth of the hair follicle where the egg matures into an adult.[4] It takes seven days for the larva to develop into an adult that is ready to reproduce sexually.[8]

Who it affects

Demodex mites are acquired shortly after birth and are considered to be normal skin fauna that increases as people age. Almost everyone has a certain degree of the Demodex mite on his or her skin.[9] Heavy infestations of Demodex can arrive in adolescence, and could last up to middle age. The increase of their food supply, sebaceous glands, proliferate during puberty, which explains the increase of infestations of mites during adolescence. Twenty-five percent of the people who are up to 20 years old have mites, and 30% of people up to the age of 50 have mites. People that are between 80 and 100 years old, between 50%-100% have mites.[5] Hair follicles in all adults are infested, but the distribution of mites varies which has a different impact on each person. Men are often more likely to be infested by mites than women because they have more sebaceous glands, thus produce more food for the mites.[7]

References

  1. ^ a b "Demodex folliculorum". zip code zoo. 2009-04-27. http://zipcodezoo.com/Animals/D/Demodex_folliculorum/. Retrieved 2009-05-31. 
  2. ^ a b c "BBC - h2g2 - The Face Mite". 3 March 2008. http://www.bbc.co.uk/dna/h2g2/A31267884. Retrieved 2009-05-31. 
  3. ^ Tullos O. Coston (1967). "Demodex folliculorum blepharitis". Transactions of the American Ophthalmological Society 65: 92–361. PMC 1310279. PMID 4229846. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1310279. 
  4. ^ a b c d e f g h "Demodex folliculorum". www.beautymagazine.com. 2010. http://www.beautymagonline.com/pages/demodex_folliculorum.htm. Retrieved 2010-12-07. 
  5. ^ a b c http://www.jashbotanicals.com/articles/demodex_folliculorum.html
  6. ^ Demodex folliculorum and hair loss
  7. ^ a b Dirk M. Elston (2010). "Demodex mites: Facts and controversies". Clinics in Dermatology 28 (5): 502–504. doi:10.1016/j.clindermatol.2010.03.006. PMID 20797509. 
  8. ^ "Disease caused by Demodex folliculorum". iyanarsip.blogspot.com. 2010. http://iyanarsip.blogspot.com/2010/05/disease-caused-by-demodex-folliculorum.html. Retrieved 2010-12-07. 
  9. ^ Albert M. Kligman & Michael S. Christensen.. "Demodex folliculorum: requirements for understanding its role in human skin disease". Journal of Investigative Dermatology 131 (1): 8–10. doi:10.1038/jid.2010.335. PMID 21157421. 

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