lice infestation

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.

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.

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.

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.

Lice infestation: treatment

For the treatment of a lice infestation there are basically three different therapeutic approaches available: the mechanical removal of the lice by means of a special comb, chemical substances and those which are physically effective. The chemically active agents attack the nervous system of the lice, while the substances with physical action close the breathing holes of the insects.

As a rule, mechanical therapy is combined with either chemical or physical treatment, because the combination of both strategies produces a much better result. The therapy is usually carried out at home by the patient or, in children, by the parents.

In order to eliminate the lice infestation safely, the therapy must be carried out consistently and correctly according to the instructions for use, which may prove difficult in practice. For example, it is important to repeat the drug treatment after about ten days, otherwise not all lice will be killed. For details on each treatment, see the sections on the different types of lice.

head lice

Even in Germany, many children suffer from head lice at least once in their lives. All you need to know about it is in the text Head Lice

Pubic lice

Pubic lice mainly affect the pubic hair, but in rare cases can also occur in other parts of the body. You can read more about this in the text Filzläuse.

body lice

An infestation with dress lice (Pediculosis corporis) takes place only under very bad hygienic conditions and is an absolute rarity in Western Europe. Occasionally, homeless people suffer when they wear their clothes for long periods of time and can not wash.

Clothes lice are about 3 to 4 millimeters in size. They appear whitish to yellowish, sometimes their color is also slightly brownish. The white eggs of the parasites have a drop-like shape and are barely visible to the naked eye.

The louse owes its name to the fact that it lives on the textile fibers of clothing, preferably on the inside of underwear. There they hook themselves with their attached at the three pairs of legs clamp organs at the seams and folds of the fabric. Occasionally, body lice are also found on body hair and in bed linen and towels. Head hairs are not affected by dress lice. The animals can move relatively fast, but are not capable of jumping.

For food intake, lice pass several times a day on the body surface of the host, where they pierce through the skin and suck blood. Then the insects go back into their clothes. Among the human lice the clothes louse shows the highest endurance capacity with lack of food. So it can survive at a temperature of about 23 degrees for up to four days without food.

Propagation of the lice

With an average lifespan of about 35 days, a female louse produces a total of about 150 to 300 eggs, which attaches them to the textile fibers of the clothing with a special, highly resistant adhesive substance. After about seven days, this causes so-called first larvae, which are around one millimeter in size. These go through two more larval stages until they are sexually mature after about 7 to 14 days. In total, the duration from oviposition to the next reproductive louse generation is 14 to 21 days.

Clothes lice are relatively sensitive to temperature changes. Their optimum is between 27 and 30 degrees, as soon as the thermometer falls below 20 degrees, the development of the clothes lice comes to a complete standstill. Excessive heat also causes the parasite to migrate so that when the body temperature of the host is raised, for example in the case of fever, they migrate to the outside of the clothing. From temperatures of 47 degrees, both the clothes lice and their eggs are completely killed.

How are clothes lice transferred?

The transmission of dressings takes place through a close and long-lasting contact from person to person – but usually by the exchange of afflicted, unwashed clothing. The sharing of bed linen and towels can also lead to a lice infestation.

Which diseases can be transmitted by lice?

In a clothes louse live numerous bacterial species. Some are dangerous pathogens to humans. The infectious diseases transmitted by dressings are:

• the typhus fever, also called Läusefleckfieber or war typhus. It causes high fever, severe body aches and the eponymous patches on the skin.
• the louse return fever (relapse fever). It shows several fever episodes, between which some symptom-free days can lie.
• the Wolhynian fever, also known as five-day fever or trench fever. This leads to sudden headaches, fever and sometimes even meningitis.

With antibiotics, these infections can usually get a good grip on lice infestation, but untreated are sometimes the result of severe cases, which in the worst case even lead to death.

How do you combat lice?

In order to get rid of clothes lice, it does not need drugs that act directly on the lice, in contrast to the treatment of head and pubic lice. Instead, one makes use of the fact that they do not live directly on the body but on clothing. With a slight lice infestation, it usually suffices if you change the clothes, bed linen and towels daily and wash at least 60 degrees. At this temperature, the lice and eggs are reliably killed.

At temperatures over 60 degrees, just one hour to get rid of the lice is enough. If it is delicate laundry that can not be washed at 60 degrees, it should be disinfected instead. Against the sometimes itching, there are in the pharmacy ointments and creams.

Furthermore, the parasites can be killed due to lack of food or cold. For example, the contaminated textiles can be sealed in a plastic bag for at least four weeks or placed in a freezer for 24 hours.

In the case of an infestation with dress lice, a doctor should always be consulted and, in addition, a report sent to the responsible health authority. In addition, an affected property may need to be cleaned by a government-approved pest control company, but only for a very strong one lice infestation.

Lice infestation: Disease course and prognosis

As long as a lice infestation is not treated specifically, the parasites can multiply undisturbed. With simple washing or normal care products, head and pubic lice can not be impressed. Only the clothes louse can be dealt with with laundry.

Already after the first treatment, however, if it has been carried out correctly, there is no longer any risk of infection of those affected. And after the second treatment is the lice infestation usually endured.