What is head lice?
The head louse (Pediculus humanus capitis) is a very small insect that belongs to the animal lice or Phthiraptera. It is one of the best known species of parasitic insects that live on human blood and one of the most widespread species. The head louse is seen as a pest. The medical term for infection with this louse Head lice infestation.
The louse adheres to the hair close to the skin and feeds on the blood that is sucked by the sucking snout. The lice are not dangerous and can not transmit diseases. An infection with head lice is called pediculosis and is by no means the result of unhygienic living as is often thought. The lice can spread rapidly in groups of people who hold an unsanitary living on it, but however has a preference for clean and washed her. Centuries ago, the head lice among the general population a normal appearance but in most Western countries, the louse is now relatively rare.
The louse causes an annoying itching of the scalp as a result of an allergic reaction of the skin to the saliva of the louse. Head lice are very contagious and can pass easily from human to human, but in particular through its direct-contact her.
The lice are like other humans parasitic animals a culture follower occurring worldwide. Head lice are easily confused with the Body louse, the latter species can transmit dangerous diseases.
Features
The lice are small, wingless insect that reaches a length of 2.5 to 3 millimeters. The color is brown to gray, the louse is somewhat translucent and sometimes you can see the red color of the aspirated blood. The color of the sluice will depend somewhat together with the pigment in the hair of its host. The abdomen is easily distinguished from the front as it thickens and is clearly segmented and slightly pear-shaped. The header contains two very small eyes with which the louse can hardly see anything and only differences between day and night can perceive. On the head are also provided two articulated antennas, which consist of five members. The suction pipe of the louse is called proboscis, is withdrawn at rest and is not visible. The tube consists of several fused with each other mouth parts, thus forming the inner lip or hypopharinx the upper food channel, the lower parts are formed from the lower lip or labium. In the middle is the salivary duct. The front of the tube is provided with saw-like teeth, with which the skin of the host is sawn open.
At the front of the body are the three pairs of legs provided, which morphologically very similar to each other. All legs end in well developed grasping claws which are well suited to cling to human hairs are not too thick. The females are usually slightly larger than males, especially if they carry eggs. The louse has the curved legs somewhat crab-like appearance. The different nymphal stages are hard to tell apart and differ mainly in size. Like the parents have the right nymphs six legs, antennae and eyes.
Nits are the eggs of the lice and are grayish-white in color. They can look very similar to dandruff. Where loose dandruff in the hair, but the nits are firmly stuck to the hair. The eggs are 1 mm and are 3-4 mm from the scalp.
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| Head lice images |
Life
The head louse feeds exclusively on human blood, an average of 3 to 6 times per day. The head louse is sensitive to a lack of food. Head lice can survive between 8-24 hours without food and heat, otherwise they dry out and die.
When sucking brings the lice are sucking mouthparts into the skin and sucks an amount of blood on. For the blood starts sucking is first placed a little saliva, that has a coagulation-inhibiting effect. Because the blood does not clot can continue sucking lice. There are very small quantities at a time sucked up, wherein the females blood considerably more need because they need to develop the eggs. However, the symptoms of lice do not come from the blood sucking himself but to the many bites holes that are applied that provide intense itching.
The favorite parts of the lice are the darkest parts of the skull, head lice hate light though this property can not be employed in the fight against lice. Head lice are most often behind the ears, because it is relatively warm and humid. The ambient temperature is very close; if it is too cold or too hot lice die soon. If a host has a fever, the lice will leave the body as well as the death of the host enters the lice go looking for a warm place.
Of head lice has been reported that girls are more easily infected due to the relatively long hair. However, this can also be explained by contamination occurs mainly by direct hair-hair contact. It is also known that people with curly hair less quickly become infected because of the curly hair type, where head lice seem to hate. Another study reported that lice in Europe have adapted to the oval of her blonde people, while lice in Africa for example, have legs that attach themselves better to flatter frizzy hair. This gives black people in Europe less lice because they can not adhere well to the hair.
Lice and man
People louse which the tailors and lice belong, lives a very long time with humans. An analysis of the DNA of the different types of lice suggests that the ancestor of the people louse originated 770,000 years ago. The Body louse arose scientists about 107,000 years ago, when people started wearing more clothes.
An infestation with lice and head lice is seen by many people as a taboo. In practice, anyone can be infected with lice and has nothing to do with unhygienic or poor lifestyle. Lice even feels more at home in clean her unwashed, greasy hair. Although head lice do not transmit diseases, they can sometimes cause secondary infections that instance become infected bite wounds. This risk is greatly increased if the wounds are scratched. If one remains crabs, wild meat can occur on the scalp, which can result in so-called Polish plait (plica polonica).
Taxonomy
The head louse is an insect belonging to the order of the animal lice called a scientific name Phthiraptera. The Dutch name 'lice' is misleading because many different insects 'louse' are often called totally not related. Examples are the aphids, wood lice and louse fly. Even some crustaceans called louse, an example is the fish louse. The format of the lice within the insect is interesting; the louse belongs to the group of winged insects (Pterygota) but does not develop wings. Like the flea, who descends from the scorpion flies, the ancestors of the lice had wings but they are in the course of evolution lost due to degeneration.
The animal lice are divided into the biting lice and sucking lice, head lice belongs to the latter group and is also the most famous representative. In addition to the lice counts the group of sucking lice more than 220 different species of which 44 are native to the Netherlands. The animal lice are a group of fairly uniform but nevertheless highly specialized insects. Most species live parasitically off the blood of mammals and birds, the two best-known species are the pubic louse and the people, the latter species is divided into two subspecies; the body or Body louse and lice. The reason for this fame is that these lice are specialized on man and his well researched. Most mammals parasitic lice are not as well studied, virtually every mammal and bird has its 'own' louse, the different types are so specialized that they can live on one particular species.
The Body louse and lice are not only closely related to each other, they are different subspecies of the same species; the people louse. Both species are anatomically the same, though the Body louse larger and relatively long antennae. Lice remains smaller is darker in color, also the chitinepantser is relatively thicker. However, both subspecies are very closely related; as a colony head lice on a hairless part of body do they seem grown stronger after a few generations the Body louse.
Distinction with other parasites
The head louse is confusing because of the unsightly little body easily with other humans living parasites. On human life different lice, mites, fleas and other invertebrates, which each have their own way of life and inhabit another body area. Because lice are usually only in the head hair manifests the louse is easy to distinguish from other blood-sucking insects that live on people. The most famous sucking lice, pubic or platje (Phthirus pubis), has legs that are built to cling relatively thick hair and can only survive in pubic hair around the anus, armpit hair and mustache, beard, eyelashes or eyebrows. The closely related but much rarer Body louse (Pediculus humanus corporis) finally is slightly larger than the pubic and head lice and can not move around very hairy areas. The Body louse is, therefore, to only to hairless parts of the body and on the inside of clothing. Although the Body louse nowadays hardly more common, it is the only louse that can transmit diseases. It used to be even a major distributor of infamous rickettsiaire diseases such as typhus.
Besides people lice are more related lice that live between the body hair of all mammals, such as the dog louse (Trichodectes canis) and the chimpanzee louse (Pediculus schaeffi). Other mammals have their specific lice are squirrels, deer, mice, horses, sheep, goats and seals, an example of a seal-louse is the kind Lepidophthirus macrorhini. Remarkably, the marsupials have no specialized lice, what to do with the relatively young existence of this group. All mentioned mammal lice pose no threat to humans; they have strongly specialized in the life of their host and can not survive on humans. It is noteworthy that some of these lice themselves, at least in laboratory conditions, may reproduce themselves, whereby they are regarded as different sub-species and not as a different species.
Another insect that can be confused with sucking lice - but not been verwant- here is the bed bug (Cimex lectularius). However, the bedbug sucks blood but does not live on humans. The bug resides in the vicinity of the bed to emerge at night come to feed.
Also the Demodex (Demodex folliculorum) lives on humans and drills into her roots and lives on the skin separated fats. This mite is only 0.1 to 0.4 millimeters long and is to be seen with the naked eye hardly. Other parasites to humans who are not to be confused, the scabies mite (Sarcoptes scabiei) and the Human flea (Pulex irritans).