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Head lice

Category: Illness or disabilities

Type

Involuntary

Introduction and description

 
 
 
 

The head louse (Pediculus humanus capitis) is an obligate ectoparasite of humans, that is a parasite that cannot reproduce without exploiting human beings.  Parasites that live on the outside of the host, either on the skin or the outgrowths of the skin, are called ectoparasites.

It causes head lice infestation (pediculosis capitis). The head louse is related to the body louse (Pediculus humanus humanus) and is distantly related to the pubic or crab louse (Pthirus pubis).  Lice infestation of any part of the body is known as pediculosis.

 

Head lice are not carriers of disease [as far as researchers are aware], in contrast to the body lice which are carriers of some very nasty diseases.  The body-louse-borne lethal diseases include ‘epidemic typhus, trench fever, relapsing fever and the classical plague’. Some of these diseases, such as trench fever caused by Bartonella quintana, are re-emerging in the United States and in other countries.

Head lice infestation is often found in children.  This is because little children share things and hug each other, or touch heads.  For example in a study of children from around 30 state primary schools in the villages and towns in eastern Poland, pediculosis was diagnosed in 2.01% of the schoolchildren, more frequently in pupils from rural (3.52%) than urban (0.98%) schools. 

 

At one time, schools employed nurses – there to handle minor bumps and grazes, and they were quick to spot cases of head lice and nip any spread in the bud, but now it is rare for any schools to have a nurse.  This may be one reason why the incidence of head lice is increasing, - the incidence of pediculosis has doubled in Poland, for example, despite the improvement in the socioeconomic status of the population observed within the last 16 years.  But this is not the only reason, this apparently annoying little insect is on the increase.  The prevalence of head lice in many countries is also increasing rapidly because of resistance to the chemicals used in many head lice treatments.

Pediculosis capitis infestations are in epidemic proportions in some parts of the United States and the world. The development of lice resistant to DDT, lindane, malathion, and permethrin and with a reduced efficacy with natural pyrethrins has resulted in the highest prevalence of head lice in the last 50 years. Parents are spending hundreds of dollars on head lice products that do not meet their purported claims. Some children in Florida have missed more than 2 months of school because of head lice or nits.[ doi:10.1016/S1040-0486(99)90005-4]

In the US, pediculosis capitis is the most prevalent parasitic infestation of children, and an estimated 6 to 12 million people are affected every year [PMID: 19104739].  But this is a world-wide problem.  Of 3,079 children in a medium-sized community near Jerusalem, for example, 11.2% were found to be infested with living lice and eggs and another 23.4% had nits. Boys and girls were equally infested. The incidence of infestation was highest among children 4-11 years of age. [PMID: 2228380].

Symptoms

Head lice infestations, are psychologically stressful, physically irritating, and are one of the leading causes of school absence.  ‘Scalp pruritus is the cardinal symptom’ – itching.

The little creatures are so small it is almost impossible to see them with the naked eye, especially in their semi-transparent as opposed to gorged state.  Thus it is the itching that tends to be a tell-tale sign, however, the bites can sometimes cause irritation and become infected leading to inflammation.

If the bites have become infected you may hear the term - Pruritus with impetiginisation. [itching and impetigo].   Impetigo is a bacterial infection and often causes a yellowish crust on the face, arms, or legs. Less commonly there may be large blisters which affect the groin or armpits. The lesions themselves may be painful or itchy. It is typically due to either Staphylococcus aureus or Streptococcus pyogenes.

 

Cause

 

Head lice are tiny (2.5–3 mm long), wingless insects, grey in general, but their precise colour varies according to the environment in which they were raised. They feed exclusively on human blood.   After feeding, consumed blood causes the louse body to take on a reddish colour.

Head lice spend their entire life on the human scalp and humans are the only known hosts of this specific parasite.  Head lice cannot fly, and their short stumpy legs render them incapable of jumping, or even walking efficiently on flat surfaces.  But their short legs and large claws, are adapted to clinging to the hair of their host, and lice can climb up strands of hair very quickly.  This is how they move from host to host via touching heads or even shared hats.

There are seven visible segments of the louse abdomen. The first six segments each have a pair of spiracles through which the insect breathes. This is important, as if one wants to asphyxiate a louse it will be via blocking these spiracles.  The last segment contains the anus and the genitalia.

 

Like most insects, head lice reproduce using eggs.  Females lay about 3–4 eggs per day and the head louse attaches its eggs to scalp hair.  In cool climates, eggs are generally laid within 3–5 mm of the scalp surface.  In warm climates, and especially the tropics, eggs may be laid 6 inches (15 cm) or more down the hair shaft.  Girls appear to be more susceptible to hair lice than boys and this may be one reason why – girls with long hair provide more opportunity for egg laying.

This also tells us that the nits need warmth to survive and hatch.  It may also explain why they are on the increase.  Now we have central heating, and children rarely go outdoors to play, or swim in the sea or other cold water, the nits are able to live in a warm, threat free paradise, even in colder climates.

To attach an egg, the adult female secretes a glue from her reproductive organ. This glue is made of proteins similar to hair keratin and quickly hardens into a "nit sheath" that covers the hair shaft and large parts of the egg except for the operculum, a cap through which the embryo breathes.

 

Each egg is oval-shaped and about 0.8 mm in length. They are bright, transparent, tan to coffee-coloured so long as they contain an embryo but appear white after hatching. Typically, the hatching time is six to nine days after oviposition.  After hatching, the louse nymph leaves behind its egg shell, still attached to the hair shaft. The empty egg shell remains in place until physically removed by abrasion, or until it slowly disintegrates, which may take 6 or more months.

Accordingly, on the head of an infested individual the following eggs could be found:

  • Viable eggs that will eventually hatch
  • Remnants of already-hatched eggs (known as ‘nits’)
  • Nonviable eggs (dead embryo) that will never hatch
 

This has produced some confusion in, for example, school policy (see The "no-nit" policy) because, of the three items listed above, only eggs containing viable embryos have the potential to infest or reinfest a host.

Head lice, when newly hatched, are called nymphs.  Newly hatched nymphs moult three times before reaching the sexually-mature adult stage.  Nymphs feed only on human blood and cannot survive long away from a host. In contrast, mature head lice can live off the head, for example on soft furnishings such as pillow cases, on hairbrushes, or on coat hoods for up to 48 hours.  In other words, it is imperative that one keeps attacking the nymphs before they become mature lice, when they can breed and spread more easily. 

Adult lice are the most mobile, indicating that they are most likely to initiate new infestations. Neither population density nor hunger significantly affected dispersal tendencies. Lice were dislodged by air movement, combs and towels, and passively transferred to fabric within 5 min. Females oviposited on a variety of substrates and 59% of eggs incubated for 8 h/night hatched after 14-16 days. PMID: 16207180

 

Pairing can begin within the first 10 hours of adult life. After 24 hours, adult lice copulate frequently, with mating occurring during any period of the night or day.  In other words, once they are adults, their entire life is devoted to reproducing.

The time required for head lice to complete their nymph development and reach maturity depends on feeding conditions. At minimum, eight to nine days is required for lice having continuous access to a human host.

Nymph hazards are numerous. Failure to completely hatch from the egg is invariably fatal and may be dependent on the humidity of the egg's environment.  Thus the egg needs warmth but it also needs humidity.

Diagnosis

Nymphs and adults are blood-feeders and bite the skin four to five times daily to feed. They inject saliva which contains an anti-coagulant and suck blood. The digested blood is excreted as dark red frass – thus this may be a tell-tale sign.  Although any part of the scalp may be colonized, lice favour the nape of the neck and the area behind the ears, where the eggs are usually laid, thus this may be the best place to start looking.

The first step is to ensure that you are not treating an old infestation.

Nits may remain glued on the hair for at least 6 months, even after a successful treatment, and lead to a false positive diagnosis of louse infestation. If nits are seen on the hair, the child should be examined, but treatment should be initiated only if living lice are found. Formulations containing 5% acetic acid or 8% formic acid, as well as acid shampoos (pH 4.5 to 5.5) and conditioners, in combination with a louse comb, can be helpful for removing nits.
Regular examination of the child's head using a louse comb is the best measure to detect re-infestation at an early stage. PMID:  10937452

There is an added hypothesis that we might add here.  The skin and the natural oils and grease secreted on hair and skin is naturally acid, and from the above it appears that the nits can be removed using acid based shampoos or conditioners.  Might it be possible that one of the causes of the increase in lice is the use of harsh shampoos on children that remove all the natural protective layers of grease and oil on their hair and on their skin?

Treatment

The options are as follows:

Insecticides

There are over the counter shampoos and medicines that contain insecticides and pesticides.  Apart from the environmental and toxicological concerns of using insecticides or pesticides on small children or anyone who may have open wounds through which the chemical can enter the body, one of the notable developments with this treatment is that it no longer works, due to the development of louse strains resistant to insecticides.

In developed countries, the infestation rate of 4- to 13-year-old children remains high despite preventive efforts. This is due to the existence of numerous ineffective pediculicides, the incorrect use of the effective agents, toxicological concerns and the development of louse strains resistant to insecticides. [Furthermore] Most pediculicides are only partially ovicidal PMID:  10937452

Suffocation

 

Suffocating does work, its only disadvantage is that the suffocating agent appears to have to be left on for some time.  Hair gels have been used, for example, presumably this was the origin of the older version of Brylcream [although I am guessing].  But anything natural will do as long as it blocks the breathing pores of the insect.  Conditioner and a swimming cap overnight has even been used in one case, and it worked

Suffocating agents such as olive, soya, sunflower and corn oils, hair gels and mayonnaise are able to kill a significant number of lice only if they are applied in liberal quantities for more than 12 hours. However, they lubricate the hair and therefore may facilitate combing and removing lice and eggs from the scalp. …..  PMID:  10937452

Although essential oils have been proposed and even proven for efficacy, there are some that simply work via suffocation, just as all the other products do; as such it can be a rather expensive option.  Furthermore, because the concentrations of chemicals in essential oils is so high, the dilution process has to be carefully worked out before it is ever used by the ‘patient’, otherwise it may not be safe, given that they often need to be left on for some time.

Communing with nature

By letting a child go outdoors on a regular basis for several hours, without a hat, in cold and rain, wind and hail, sleet and snow, but where the child’s body is well wrapped up and warm, the lice will undoubtedly disappear.  Head lice do not like cold weather and if the wind whips though the hair, the lice and their eggs will have nowhere to go.  Give them a bike, or get them sledging [the children, not the lice].  It all helps.

Heat and dessication

There are products on the market that use heat and hot air to dessicate both lice and eggs, but a hair dryer with controlled, directed heated air has been just as effective. The hair dryer and heated air is best directed by a third party as they are able to see where to use it.

The use of heated air is appealing because it is a fast, safe, nonchemical treatment. Head lice are also unlikely to evolve resistance to desiccation, which is the apparent mode of action. PMID: 21337950

There is one very real disadvantage with using hot air, however, adult lice can travel on air to find new homes and are fully capable of surviving to lay eggs.  Thus you may think you’ve dislodged them from your hair, but you may have blown them all over everyone else.  As such we consider the following approach may be more effective and more socially acceptable.

Body lice are treated in some parts of the world using saunas, dry heat only, as such the same treatment may work for head lice, although we could find no papers to confirm this.  The use of a sauna and cold plunge bath [head right under the water] as long as the heart can take it, may also be efficacious.

Combs

 

Fine tooth lice combs fall into two classes based on the material from which their teeth are made: plastic or metal. Metal combs are further divided into those that are made from a flat sheet of metal, and hence have rectangular teeth, and those that have cylindrical teeth embedded in a plastic base.  In tests [see references], metal combs seem to have performed better than plastic.

The principal reason why metal seems to be better, is because it is rigid, tough and unbreakable and the space between the comb teeth can be much smaller and the length kept longer.  Furthermore an edge can be given to the teeth [rectangular teeth] so that they are in effect acting like scrapers – which given the glue used by the insect to adhere the egg to the hair shaft is important and needed.

Regular examination of the child's head using a louse comb is the best measure to detect re-infestation at an early stage. Educating caregivers, nurses and teachers about louse biology, epidemiology, prevention and control is of paramount importance. The psychological effect of an infestation with lice is significant and often associated with anxiety and fear. The child should not be made to feel responsible for having lice, or be punished or reprimanded.  PMID:  10937452

 

How it works

There is nothing at all to suggest that hair lice give one a spiritual experience – hallucination or any other experience.  We do have some observations, however, on approaches for treatment.

Furthermore, it is extremely clear that if you get an hallucination and you have head lice, then the cause is likely to be the pharmaceutical you are using to treat it – the insecticide and pesticide based drugs.

References and further reading

  • Ann Agric Environ Med. 2015;22(4):599-603. doi: 10.5604/12321966.1185760. Head pediculosis in schoolchildren in the eastern region of the European Union. Bartosik K1, Buczek A1, Zając Z1, Kulisz J.  1Chair and Department of Biology and Parasitology, Medical University, Lublin, Poland.  PMID:  26706962
  • Ann N Y Acad Sci. 1975;266:6-24.  Modification of antityphus antibodies on passage through the gut of the human body louse with discussion of some epidemiologic and evolutionary implications.  Wisseman CL Jr, Boese JL, Waddell AD, Silverman DJ.
  • Int J Dermatol. 2007 Dec;46(12):1275-8. doi: 10.1111/j.1365-4632.2007.03410.x.  Comparative efficacy of two nit combs in removing head lice (Pediculus humanus var. capitis) and their eggs.  Speare R1, Canyon DV, Cahill C, Thomas G.- PMID: 18173523
  • Parasitol Res. 2013 Mar;112(3):1363-6. doi: 10.1007/s00436-012-3208-z. Epub 2012 Dec 2.  Comparative efficacy of commercial combs in removing head lice (Pediculus humanus capitis) (Phthiraptera: Pediculidae).  Gallardo A1, Toloza A, Vassena C, Picollo MI, Mougabure-Cueto G. PMID:  23212391
  • Paediatr Drugs. 1999 Jul-Sep;1(3):211-8.  Prevention and treatment of head lice in children.  Mumcuoglu KY1.  1Department of Parasitology, Hebrew University-Hadassah Medical School, Jerusalem, Israel. kostam@cc.huji.ac.il
  • Biochem J. 1952 Sep;52(1):54-8.  Volatile acids in the secretion products, hair grease, of the skin.  BROUWER E, NIJKAMP HJ.  PMID:  13018162
  • Complement Ther Nurs Midwifery. 1996 Aug;2(4):97-101.  The potential effectiveness of essential oils as a treatment for headlice, Pediculus humanus capitis.  Veal L1.  1British Embassy, Reykjavik, Iceland.
  • Fam Pract. 2016 Feb;33(1):23-9. doi: 10.1093/fampra/cmv081. Epub 2015 Oct 28.  Head lice predictors and infestation dynamics among primary school children in Norway.  Birkemoe T1, Lindstedt HH2, Ottesen P2, Soleng A2, Næss Ø3, Rukke BA4.
  • Int J Dermatol. 2005 Oct;44(10):811-6. Transmission potential of the human head louse, Pediculus capitis (Anoplura: Pediculidae).  Takano-Lee M1, Edman JD, Mullens BA, Clark JM.
  • Isr Med Assoc J. 2002 Oct;4(10):790-3.  The in vivo pediculicidal efficacy of a natural remedy.  Mumcuoglu KY1, Miller J, Zamir C, Zentner G, Helbin V, Ingber A.  1Department of Parasitology, Hebrew University Medical School, Jerusalem, Israel. kostam@cc.huji.ac.il  PMID:  12389342
  • J Insect Physiol. 2011 Oct;57(10):1450-2. doi: 10.1016/j.jinsphys.2011.07.011. Epub 2011 Jul 23.  Human lice show photopositive behaviour to white light.  Mougabure-Cueto G1, Picollo MI, Lazzari CR.  1Centro de Investigaciones de Plagas e Insecticidas (CONICET), Juan Bautista de La Salle 4397, Buenos Aires, Argentina. gmougabure@citefa.gov.ar
  • Osong Public Health Res Perspect. 2015 Dec;6(6):346-56. doi: 10.1016/j.phrp.2015.10.011. Epub 2015 Nov 9. Prevalence of Head Lice Infestation and Its Associated Factors among Primary School Students in Iran: A Systematic Review and Meta-analysis.  Moosazadeh M1, Afshari M2, Keianian H3, Nezammahalleh A3, Enayati AA1.

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