ICD codes for this disease: ICD codes are internationally valid medical diagnosis codes. They are found e.g. in medical reports or on incapacity certificates. B85ArtikelübersichtLäusebefall
- Causes and risk factors
- Examinations and diagnosis
- body lice
- Disease course and prognosis
Lice infestation: description
A lice infestation is usually very annoying for those affected, but generally more dangerous. For a better understanding of the disease, the lice biology and related terms are explained in detail.
What are lice?
Lice are parasitic insects and as such always rely on a host to feed on. Parasites can either live in or on their host, the latter is the case, called the parasites as ectoparasites. In addition to lice, this group includes, for example, fleas, ticks or leeches. Lice live permanently on their host and do not leave it, except in the case of a direct transition to another host (transmission).
A colonization with parasites that do not multiply in their host, is correctly referred to as an infestation, and in connection with a lice infestation over and over again from "infections" hears or reads.
The different animal species prefer each host and are adapted to this. So there are among others dog lice, seal lice, pig lice and just human lice. A transmission of lice between different species or between humans and animals is very rare, so that for a lice infestation in humans, referred to in the jargon as pediculosis, actually only human lice (Pediculidae) come into question.
Which species can cause a lice infestation in humans?
Within the Pediculidae there are three representatives who can tamper with man. The best known and most common is the head louse (Pediculus humanus capitis). In addition, there are still in this country much rarer felt and clothing lice (Pthirus pubis, Pediculus humanus humanus). Although it is not yet clear whether the clothes louse and the head lice each represent their own species, or only two different subspecies of the human louse, for the diagnosis and treatment in a lice infestation does not matter.
Lifestyle and reproduction of the human lice
Like all so-called "real" animal lice, lice feed on the blood of their host. They are equipped with special mouth tools that allow them to penetrate the skin of the host and to suck his blood. They also put some saliva in the branch canal, which ensures that the blood does not clot and provides the typical symptoms of a lice infestation. The same principle applies to mosquitoes. A louse takes a blood meal several times a day and can survive only a few days without a host.
Human lice live in the hair, or in the clothing of the host and cling there with their claw pairs there. Depending on the type, they prefer certain parts of the body. The reproduction takes place on the one hand by classical intersex sexual mating, but partly also by unisexual virgenesis (parthenogenesis), in which a female animal without male fertilization lays viable eggs.
These are covered with a solid chitin shell and are attached by the lice to the hair of the host or textile fibers of clothing. And that water insoluble, which is why the eggs in a lice infestation can not be easily washed out. The term "Nissen" sometimes refers to the eggs, but sometimes only the remaining chitin shells, after the hatchlings are already hatched.
The newly hatched Läuselarven, which are also called nymphs, externally similar to the adult animals, but are much smaller and barely visible to the naked eye. They go through various stages of development until they are sexually mature after about ten days and can even lay new eggs.
Who is affected by a lice infestation?
In principle, anyone can be affected by lice. However, especially for felts and clothes lice the hygienic circumstances for the distribution play an essential role, so that they occur mainly in poorer countries and in crisis areas. In Western Europe, lice are only rarely the cause of lice infestation. Head lice behave differently because hygiene has little impact on infection. Therefore, they are still common in our climes, mainly affecting children.To the table of contents
Lice infestation: symptoms
The symptoms of a lice infestation are caused by the stitches of the parasites. The injected saliva is recognized by the body as a foreign substance and triggers a small immune response, which manifests itself in the form of reddened nodules and wheals. In addition, there is usually a strong itching, which makes those affected scratchy. This in turn leads to a superficial damage to the skin, which is thus more susceptible to infestation with bacteria and fungi.
If it comes to the scratched spots to an infection with bacteria, the skin becomes inflamed additionally and it sometimes produces yellowish crusts. Such a complication is called impetignation.
Apart from the unpleasant symptoms and the often existing mental stress, a lice infestation does not pose any health risks. However, lice are possible carriers of various bacteria, which can sometimes lead to severe febrile illnesses.To the table of contents
Lice infestation: causes and risk factors
Since human lice are virtually absent in animals, an infection is almost exclusively from person to person, or in the clothes louse on infested clothing. For transmission, direct body contact is necessary because the lice usually do not leave the host body.
The longer the body contact stops, the greater the transmission risk. Unlike fleas, lice do not jump. In order to be able to pass on to a new host, they need a certain amount of time, because they have to cling to their hair with their claws. By short touches such a transmission does not usually happen.To the table of contents
Lice infestation: examination and diagnosis
A lice infestation is detected by inspection, so by the recognition of the lice or the eggs with the naked eye. Further examinations are then no longer necessary. The symptoms are an indication, but are not sufficient for a diagnosis alone, as they may have other causes such as a flea infestation.
If suspected lice infestation, the hair or clothing must be thoroughly searched. Tools such as a magnifying glass or a lice comb facilitate the search. If no lice / nits are found, a lice infestation is not yet excluded, as it can always be that either adult animals have been overlooked, or the existing lice are still in much smaller nymphal stage.
Conversely, the nits left after hatching are not evidence of active lice infestation. Because it may be that all lice have already been killed with a chemical or physical treatment, but the egg shells are still in the hair, because they were not removed. However, if empty eggs are found in the hair, but no treatment has been done before, it can be assumed that a lice infestation is present, as the parasites usually do not disappear by themselves.