Head lice infestation

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This article is about the infestation. For for the animal, see Head louse.
Head lice infestation (pediculosis capitis)
Classification and external resources
Fig.4.Louse bites.jpg
Head lice bites on the back of the neck
ICD-10 B85.0
DiseasesDB 9725
MedlinePlus 000840
eMedicine med/1769
MeSH D010373

Head lice infestation (also known as pediculosis capitis,[1] nits[2] or cooties[3]) is the infection of the head hair and scalp by the head louse (Pediculus humanus capitis).[4] Itching from lice bites is a common.[5] During a person's first infection the itch may not develop for up to six weeks.[5] If a person is infected again symptoms may begin much more quickly.[5] The itch may cause problems with sleeping.[6] Generally; however, it is not a serious condition.[7] While head lice appear to spread some other diseases in Africa they do not appear to do so in Europe or North America.[4][6]

Head lice are spread by direct contact with the hair of someone who is infected.[6] The cause of head lice infestations are not related to cleanliness.[5] Other animals such as cats and dogs do not play a role in transmission.[6] Head lice feed only on human blood and are only able to survive on human head hair.[4][5] When adults they are about 2 to 3 mm long.[8] When not attached to a human they are unable to live beyond three days.[5] Humans can also become infected with two other lice — the body louse and the crab louse. To make the diagnosis, live lice must be found.[5] Using a comb can help with detection.[5] Empty eggshells (known as nits) are not sufficient for the diagnosis.[5]

Possible treatments include: combing the hair frequently with a fine tooth comb or shaving the head completely. A number of topical medications are also effective including: malathion, invermectin and dimeticone.[7] Dimeticone, which is a silicone oil, is often preferred due to the low risk of side effects.[7] Pyrethroids such as permethrin have been commonly used; however, have become less effective due to increasing resistance.[7] This is little evidence for alternative medicines.[9]

Head-lice infestations are common, especially in children.[5] In Europe they infect between 1 and 20% of different groups of people.[4] In the United States between 6 to 12 million children are infected a year.[6] They occur more often in girls than boys.[5] It has been suggested that historically, head lice infection were beneficial as they protected against the more dangerous body louse.[10] Infestations may cause stigmatization of the infected individual.[5]

Signs and symptoms[edit]

Adult male (left) and female (right) head lice

Head lice is generally uncomfortable but typically not serious condition.[7] The most common symptom is itching of the head which normally worsens 3 to 4 weeks after the initial infestation.[citation needed] The bite reaction is very mild and it can be rarely seen between the hairs. Bites can be seen, especially in the neck of long-haired individuals when the hair is pushed aside. Swelling of the local lymph nodes and fever are rare. Itching may cause skin breakdown and uncommonly result in a bacteria infection.[7]

In Ethiopia head lice appear to be able to spread louse-born epidemic typhus and Bartonella quintana.[4] In Europe the head lice do not appear to carry these infections.[4]

Cause[edit]

Head lice are generally spread through direct head-to-head contact with an infested person.[5] Transmission by sharing bedding or clothing such as headwear is much less common.[11] The cause of head lice infestations are not related to cleanliness.[5]

Body lice are spread through direct contact with the body, clothing or other personal items of a person already carrying lice. Pubic lice are most often spread by intimate contact with an infested person. Head lice occur on the head hair, body lice on the clothing, and pubic lice mainly on the hair near the groin. Lice cannot burrow into the skin.

Diagnosis[edit]

Lice comb (Bug Buster) wet combing with conditioner for diagnosis and treatment. Head lice can be seen in foam.

The condition is diagnosed by finding live lice in the hair.[5] Finding empty eggs is not enough.[5] This is made easier by using a magnifying glass or running a comb through the child's hair. In questionable cases, a child can be referred to a health professional. However, the condition is overdiagnosed, with extinct infestations being mistaken for active ones. As a result, lice-killing treatments are more often used on noninfested than infested children.[12] The use of a louse comb is the most effective way to detect living lice.[13] With both methods, special attention should be paid to the area near the ears and the nape of the neck. The use of a magnifying glass to examine the material collected between the teeth of the comb could prevent misdiagnosis.

The presence of nits alone, however, is not an accurate indicator of an active head louse infestation. Generally, white nits are empty egg casings, while brown nits may still contain viable louse larva. One way of determining the nit is to squeeze it between two fingernails, it gives a characteristic snapping pop sound as the egg bursts. Children with nits on their hair have a 35–40% chance of also being infested with living lice and eggs.[13][14] If lice are detected, the entire family needs to be checked (especially children up to the age of 13 years) with a louse comb, and only those who are infested with living lice should be treated. As long as no living lice are detected, the child should be considered negative for head louse infestation. Accordingly, a child should be treated with a pediculicide ONLY when living lice are detected on his/her hair (not because he/she has louse eggs/nits on the hair and not because the scalp is itchy).[15]

Prevention[edit]

World War II-era American poster, created to prevent outbreaks of pediculosis among servicemen.

Examination of the child’s head at regular intervals using a louse comb allows the diagnosis of louse infestation at an early stage. Early diagnosis makes treatment easier and reduces the possibility of infesting others. In times and areas when louse infestations are common, weekly examinations of children, especially those 4–15 yrs old, carried out by their parents will aid control. Additional examinations are necessary if the child came in contact with infested individuals, if the child frequently scratches his/her head, or if nits suddenly appear on the child’s hair. Keeping long hair tidy could be helpful in the prevention of infestations with head lice.

Clothes, towels, bedding, combs and brushes, which came in contact with the infested individual, can be disinfected either by leaving them outside for at least 2 weeks or by washing them at 60 °C(140 degrees F) for 30 minutes.[16] This is because adult lice can survive only one to two days without a blood meal, and are highly dependent on human body warmth.[17] An insecticidal treatment of the house and furniture is not necessary.

Treatment[edit]

There are a number of treatments effective for head lice. These methods include combs, shaving, medical creams, and hot air.[18] Medical creams usually require two treatments a week apart.[7]

Mechanical measures[edit]

Shaving the head can effectively treat lice.[7] Wet combing a few times a day for a few weeks may also get rid of the infestation in half of people.[7] This requires the use of a special lice comb with extra fine teeth.[7] This is the recommended method for infants and women who are pregnant.[7]

Another treatment is the use of heated air applied by a blow dryer.[18]

Medications[edit]

There are many medications which can kill lice. Dimeticone is between 70 and 97% effective with a low rate of side effects and thus is seen as the preferred treatment.[7] It works by physical means and there is no evidence of resistance.[4] Invermectin is around 80% effective but can cause local skin irritation. Malathion has an effectiveness around 90% but there's the possibility of toxicity.[7] Pyrethroids such as permethrin while commonly used have lower rates of effectiveness due to the resistance among lice.[7] Effectiveness varies from 10 to 80% depending on the population studied.[5][7] Medications within a lotions appear to work better than those within a shampoo.[7]

Alternative medicine[edit]

Tea tree oil has been promoted as a treatment for head lice; however, there is disagreement on its effectiveness.[19][20][21] A 2012 review of head lice treatment recommended against the use of tea tree oil for children because it could cause skin irritation or allergic reactions, because of contraindications, and because of a lack of knowledge about the oil's safety and effectiveness.[22] Other home remedies such as putting vinegar, isopropyl alcohol, olive oil, mayonnaise, or melted butter under a shower cap have been disproven.[9] The CDC states that swimming has no effect on lice, and can decrease the effectiveness of some treatments.[23]

Environment[edit]

After treatment, people are often instructed to wash all bedding and vacuum all areas the head may have been such as car seats, coat hoods and sofas, but this is not always necessary since adult lice will die within 2 days without a blood meal, and newly hatched lice die within minutes of hatching.[18] Combs and brushes may be deloused in boiling water for 5–10 minutes. Items may also be frozen for 24 hours well below the freezing point of water to ensure that ice crystals form within the cells of the lice.[24]

Epidemiology[edit]

The number of cases of human louse infestations (or pediculosis) has increased worldwide since the mid-1960s, reaching hundreds of millions annually.[26] It is estimated between 1 to 20% of specific groups in Europe are infected.[4]

Despite improvements in medical treatment and prevention of human diseases during the 20th century, head louse infestation remains stubbornly prevalent. In 1997, 80% of American elementary schools reported at least one outbreak of lice.[27] Lice infestation during that same period was more prevalent than chicken pox.[27]

About 6–12 million children between the ages of 3 and 11 are treated annually for head lice in the United States alone.[11] High levels of louse infestations have also been reported from all over the world including Israel, Denmark, Sweden, U.K., France and Australia.[15][28]

The number of children per family, the sharing of beds and closets, hair washing habits, local customs and social contacts, healthcare in a particular area (e.g. school) and socioeconomic status were found to be significant factors in head louse infestation[citation needed]. Girls are 2–4 times more frequently infested than boys[citation needed]. Children between 4 and 13 years of age are the most frequently infested group.[29] In the U.S., African-American children have lower rates of infestation.[11]

The United Kingdom's National Health Service[citation needed] and many American health agencies [1][2][3] report that lice "prefer" clean hair because it's easier to attach eggs and to cling to the strands; however, this is often contested.

Head lice (Pediculus humanus capitis) infestation is most frequent on children aged 3–10 and their families.[30] Females get head lice twice as often as males,[30] and infestation in persons of Afro-Caribbean or other black descent is rare because of hair consistency.[30] But these children may have nits that hatch and the live lice could be transferred by head contact to other children.[31]

Other animals[edit]

Lice infestation in general is known as pediculosis, and occurs in many mammalian and bird species.[32] They are not the same organism as that which causes head lice infestations in humans.

See also[edit]

  • To a Louse (on a lady's bonnet). Perhaps the most widely known cultural reference to pediculosis capitis, occurring in a noted poem by Robert Burns.

References[edit]

  1. ^ Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0. 
  2. ^ "How to treat nits". nhs.uk. 2012-09-14. Retrieved 23 October 2014. 
  3. ^ "cootie". http://dictionary.reference.com/. Retrieved 23 October 2014. 
  4. ^ a b c d e f g h Feldmeier, H (Sep 2012). "Pediculosis capitis: new insights into epidemiology, diagnosis and treatment.". European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology 31 (9): 2105–10. doi:10.1007/s10096-012-1575-0. PMID 22382818. 
  5. ^ a b c d e f g h i j k l m n o p q Smith, CH; Goldman, RD (Aug 2012). "An incurable itch: head lice.". Canadian family physician Medecin de famille canadien 58 (8): 839–41. PMID 22893334. 
  6. ^ a b c d e "Parasites - Lice - Head Lice Frequently Asked Questions (FAQs)". cdc.gov. September 24, 2013. Retrieved 23 October 2014. 
  7. ^ a b c d e f g h i j k l m n o p "Head lice. Dimeticone is the pediculicide of choice.". Prescrire Int. 151 (23): 187–90. Jul 2014. PMID 25162097. 
  8. ^ "Parasites - Lice - Head Lice". cdc.gov. September 24, 2013. Retrieved 23 October 2014. 
  9. ^ a b Takano-Lee M, Edman JD, Mullens BA, Clark JM (December 2004). "Home remedies to control head lice: assessment of home remedies to control the human head louse, Pediculus humanus capitis (Anoplura: Pediculidae)". Journal of Pediatric Nursing 19 (6): 393–8. doi:10.1016/j.pedn.2004.11.002. PMID 15637580. 
  10. ^ Rózsa, L; Apari, P (May 2012). "Why infest the loved ones--inherent human behaviour indicates former mutualism with head lice.". Parasitology 139 (6): 696–700. doi:10.1017/S0031182012000017. PMID 22309598. 
  11. ^ a b c Division of Parasitic Diseases (DPD), National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED) (May 16, 2008). "Head lice fact sheet". Centers for Disease Control and Prevention website. Atlanta, GA: Department of Health and Human Services, US Government. Retrieved 28 May 2010. 
  12. ^ Pollack RJ, Kiszewski AE, Spielman A; Kiszewski; Spielman (2000). "Overdiagnosis and consequent mismanagement of head louse infestations in North America". The Pediatric Infectious Diseases Journal 19 (8): 689–93. doi:10.1097/00006454-200008000-00003. PMID 10959734. 
  13. ^ a b Mumcuoglu KY, Friger M, Ioffe-Uspensky I, Ben-Ishai F, Miller J; Friger; Ioffe-Uspensky; Ben-Ishai; Miller (2001). "Louse comb versus direct visual examination for the diagnosis of head louse infestations". Pediatric dermatology 18 (1): 9–12. doi:10.1046/j.1525-1470.2001.018001009.x. PMID 11207962. 
  14. ^ Williams LK, Reichert A, MacKenzie WR, Hightower AW, Blake PA; Reichert; MacKenzie; Hightower; Blake (2001). "Lice, nits, and school policy". Pediatrics 107 (5): 1011–5. doi:10.1542/peds.107.5.1011. PMID 11331679. 
  15. ^ a b Mumcuoglu, Kosta Y.; Barker CS; Burgess IF; Combescot-Lang C; Dagleish RC; Larsen KS; Miller J; Roberts RJ; Taylan-Ozkan A. (2007). "International Guidelines for Effective Control of Head Louse Infestations". Journal of Drugs in Dermatology 6 (4): 409–14. PMID 17668538. 
  16. ^ Kidshealth.org – Head lice, page-3
  17. ^ University of Florida Dept of Entomology Circular 175
  18. ^ a b c Goates BM, BM et al. (5 November 2006). "An Effective Nonchemical Treatment for Head Lice: A Lot of Hot Air". Pediatrics (American Academy of Pediatrics) 118 (5): 1962–1970. doi:10.1542/peds.2005-1847. PMID 17079567. Retrieved 2010-08-02. 
  19. ^ Barker SC, Altman PM (2010). "A randomised, assessor blind, parallel group comparative efficacy trial of three products for the treatment of head lice in children--melaleuca oil and lavender oil, pyrethrins and piperonyl butoxide, and a 'suffocation' product". BMC Dermatology 10: 6. doi:10.1186/1471-5945-10-6. PMC 2933647. PMID 20727129. 
  20. ^ Jacobi, Tillmann (22 September 2011). "The Basics – The management of head lice". GP: 38. All in all, the evidence for alternative treatments, such as tea tree oil and neem seed oil, remains weak. 
  21. ^ "Tea tree oil". Medline Plus, a service of the U.S. National Library of Medicine from the National Institutes of Health. 27 July 2012. 
  22. ^ Eisenhower, Christine; Farrington, Elizabeth Anne (2012). "Advancements in the Treatment of Head Lice in Pediatrics". Journal of Pediatric Health Care 26 (6): 451–61; quiz 462–4. doi:10.1016/j.pedhc.2012.05.004. PMID 23099312. 
  23. ^ "CDC – Frequently Asked Questions – Healthy Swimming & Recreational Water – Healthy Water". Cdc.gov. 2012-10-22. Retrieved 2012-11-22. 
  24. ^ Michigan Head Lice Manual. State of Michigan. 2004. [page needed]
  25. ^ Hootman J (April 2002). "Quality improvement projects related to pediculosis management". The Journal of school nursing : the official publication of the National Association of School Nurses 18 (2): 80–6. doi:10.1177/10598405020180020401. PMID 12017250. 
  26. ^ Norman G. Gratz (1998). "Human lice: Their prevalence, control and resistance to insecticides. A review 1985–1997" (PDF). Geneva, Switzerland: World Health Organization. Retrieved 2008-01-02. 
  27. ^ a b "A modern scourge: Parents scratch their heads over lice". Consumer Reports. February 1998. pp. 62–63. Retrieved 2008-10-10. 
  28. ^ Ian Burgess (2004). "Human Lice and their Control". Annual Review of Entomology (Annual Reviews) 49: 457–481. doi:10.1146/annurev.ento.49.061802.123253. PMID 14651472. 
  29. ^ Mumcuoglu KY, Miller J, Gofin R et al. (September 1990). "Epidemiological studies on head lice infestation in Israel. I. Parasitological examination of children". International Journal of Dermatology 29 (7): 502–6. doi:10.1111/j.1365-4362.1990.tb04845.x. PMID 2228380. 
  30. ^ a b c Nutanson I. et al. (2008). "Pediculus humanus capitis: an update". Acta Dermatoven 17 (4): 147–59. 
  31. ^ James GH Dinulos (September 2008). "Lice (Pediculosis)". The Merck Manual. Merck & Co., Inc. Retrieved 2008-12-27. 
  32. ^ "Lice (Pediculosis)". The Merck Veterinary Manual. Whitehouse Station, NJ USA: Merck & Co. 2008. Retrieved 2008-10-08. 

External links[edit]