Lice infestation
Marian Grosser studied human medicine in Munich. In addition, the doctor, who was interested in many things, dared to make some exciting detours: studying philosophy and art history, working on the radio and, finally, also for a Netdoctor.
More about the experts All content is checked by medical journalists.Lice infestation means the colonization of humans with lice. The particularly widespread head louse, the felt louse and the clothing louse are particularly relevant. Infection with the blood-sucking parasites is unpleasant, but lice infestation does not have any serious health consequences. However, disease can sometimes be transmitted through the lice. Read more about the reasons, dangers, and treatment of lice infestation.
ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. B85
Lice infestation: description
A lice infestation is usually very annoying for those affected, but usually less dangerous. For a better understanding of the disease, the biology of the lice will first be explained in more detail here.
What are lice?
Lice are parasitic insects and, as such, always depend on a host to feed on. Parasites can either live in or on their host - if the latter is the case, the parasites are called ectoparasites. In addition to lice, this group also includes, for example, fleas, ticks and leeches. Lice live permanently on their host and usually 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, whereby one hears or reads of "infection" again and again in connection with a lice infestation.
The various animal lice species each prefer certain hosts and are adapted to them. There are, for example, dog lice, seal lice, pig lice and human lice. A transmission of lice between different animal species or between humans and animals occurs only very rarely. So actually only human lice come into question for a lice infestation in humans (called pediculosis). They come from the group of Pediculidae.
Important human lice
Within the Pediculidae there are three representatives that can cause problems for humans. The best known and most common is the head louse (Pediculus humanus capitis). In addition, there are pub lice (Pthirus pubis), which are much rarer in this country, and clothes lice (Pediculus humanus humanus). It has not yet been clarified whether the body louse and the head louse each represent their own species or whether they are just two different subspecies of the human louse. However, this does not play a role in the diagnosis and treatment of a corresponding lice infestation.
Way of life and reproduction of human lice
Like all so-called "real" animal lice, human lice feed on their host's blood. To do this, they are equipped with special mouthparts that enable them to penetrate the host's skin and suck its blood. They also release some saliva into the bite channel, which ensures that the blood does not clot (like mosquitoes). It triggers the typical symptoms of a lice infestation. A louse eats blood meals several times a day and can only survive for a few days without a host.
Human lice live in the hair or in the clothing of the host and cling to it with their pairs of claws. Depending on the type, they prefer certain parts of the body. Reproduction takes place on the one hand through classic inter-sex pairing, but partly also through single-sex virgin generation (parthenogenesis). A female animal lays viable eggs without male fertilization.
The eggs of the human lice are covered with a solid chitin shell and are attached by the lice to the hair of the host or textile fibers of the clothing - and they are insoluble in water, which is why the eggs cannot simply be washed out in the event of a lice infestation. The term “nits” sometimes means the eggs, but sometimes only the chitin shells that have remained after the young animals have hatched.
The newly hatched louse larvae, also known as nymphs, already look similar to the adult animals, but are much smaller and can hardly be seen with the naked eye. They go through various stages of development until they are sexually mature after about ten days.
Who is affected by a lice infestation?
In principle, everyone can be attacked by lice. However, especially for pubic lice and clothing lice, the hygienic conditions play an essential role for the spread, so that they mainly occur in poorer countries and in crisis areas. In Western Europe, clothes lice are rarely the cause of lice infestation. It is different with head lice, because here hygiene has little influence on infection. That is why they are still widespread in our regions, mainly affecting children.
Lice infestation: symptoms
The symptoms of a lice infestation are caused by the stings of the parasites. The injected saliva is recognized by the body as a foreign substance and triggers a small immune reaction - reddened nodules and wheals form. In addition, there is usually severe itching, which causes many affected people to scratch their sores.The scratched areas can easily become infected, for example with bacteria. Then the skin becomes inflamed and yellowish crusts sometimes appear. The additional bacterial infection of the skin with another pre-existing skin disease is called impetiginization.
Apart from the unpleasant symptoms and the psychological stress that is often present, a lice infestation does not in itself pose any health risks. However, clothes lice are possible carriers of various bacteria that can sometimes lead to severe fevers.
Lice infestation: causes and risk factors
Since human lice are practically non-existent in animals, infection runs almost exclusively from person to person or, in the case of the clothing louse, via infected clothing. Direct body contact is necessary for transmission as the lice usually do not leave the host body.
The longer the physical contact, the greater the risk of transmission. Lice need a certain amount of time to crawl from one host to the other. Such a transmission does not normally occur through only brief touches.
Lice infestation: examination and diagnosis
A lice infestation is usually detected by inspection, i.e. by recognizing the lice or the eggs with the naked eye. To do this, hair or clothing must be thoroughly searched. Aids such as a magnifying glass or a lice comb make the search easier.
If no lice / nits are found, a lice infestation cannot be ruled out, as it is always possible that either adult animals have been overlooked or the lice present are still in the much smaller nymph stage.
Conversely, the nits that remain after hatching are not sufficient evidence of an active lice infestation. Because it is possible that all the lice have already been killed with a chemical or physical treatment, but the egg shells can still be found in the hair because they were not removed. However, if empty eggs are found in the hair, but no treatment has been carried out before, it can be assumed that there is a lice infestation - the parasites usually do not go away on their own.
Symptoms such as itching and reddish skin wheals are insufficient for a diagnosis of lice infestation. They can also have other causes such as a flea infestation.
Lice infestation: treatment
There are basically three different therapeutic approaches available for treating a lice infestation:
- mechanical elimination of lice using a special comb
- Treatment with chemical substances (these attack the lice's nervous system, thereby killing them)
- Treatment with physically active substances (these close the insects' breathing holes so that they suffocate)
Usually mechanical therapy is combined with either chemical or physical treatment. This can be used to achieve far better results than with a single strategy alone. Therapy is usually carried out at home by the patient himself or - in the case of children - by the parents.
In order to safely eliminate the lice infestation, the therapy must be carried out consistently and correctly as directed. For example, it is important to repeat the drug treatment after about ten days, otherwise not all lice will be killed. You can find out more about the respective treatment in the sections on the different types of lice.
head lice
In Germany, too, many children suffer from head lice at least once in their lives. You can find out everything you need to know about the widespread parasites and their treatment in the text head lice.
Pubic lice
Pubic lice mainly attack the pubic hair, but in rare cases can also occur on other parts of the body. You can read more about this and about the correct treatment in the text pubic lice.
Clothes lice
An infestation with clothes lice (Pediculosis corporis) only takes place under hygienically very poor conditions and is an absolute rarity in Western Europe. Occasionally, homeless people suffer when they wear their clothes for long periods of time and cannot wash them.
Clothes lice grow to around 3 to 4 millimeters. They appear whitish to yellowish, sometimes also slightly brownish. The parasite's white eggs have a teardrop-like shape and are barely visible to the naked eye.
The clothing louse owes its name to the fact that it lives on the textile fibers of clothing, preferably on the inside of underwear. There, the parasites hook themselves into the seams and folds of the fabric with the clamp organs of their three pairs of legs. Occasionally, clothes lice can also be found on body hair and in bed linen and towels. However, scalp hair is not attacked by clothes lice. The animals can move relatively quickly, but they cannot jump.
To eat, clothes lice pass over to the surface of the host's body several times a day, where they sting through the skin and sucking blood. Then the insects go back into their clothes. Among the human lice, the clothing louse shows the highest endurance when there is a lack of food. It can survive up to four days without food at a temperature of around 23 degrees.
However, clothes lice are relatively sensitive to changes in temperature. Their optimum is between 27 and 30 degrees. If the thermometer falls below 20 degrees, the development of the clothes lice comes to a complete standstill. Too much heat is also a problem for the parasite. If the host's body temperature rises (for example in the event of a fever), they therefore migrate to the outside of the clothing. From temperatures of 47 degrees, both the clothes lice and their eggs are completely killed.
Multiplication of clothes lice
With an average lifespan of around 35 days, a female louse produces a total of around 150 to 300 eggs. She attaches these to the textile fibers of the clothing with a special, extremely resistant adhesive substance. After around seven days, so-called first larvae hatch from the eggs and are around one millimeter in size. They go through two more larval stages until they are sexually mature after about 7 to 14 days. Overall, the time from oviposition to the next reproductive generation of lice is 14 to 21 days.
How are clothes lice transmitted?
The transmission of clothes lice can occur through close and long-lasting contact from person to person. As a rule, however, it happens through the exchange of infected, unwashed clothing. Sharing bed linen and towels can also lead to such a lice infestation.
What diseases can clothes lice transmit?
Numerous types of bacteria live in a clothing louse. Some are dangerous pathogens for humans. The infectious diseases transmitted by clothes lice are:
- Typhus, also called typhus or typhus. It causes a high fever, severe pain in the limbs and the eponymous spots on the skin.
- Relapsing lice fever (relapsing fever). It causes several attacks of fever, between which there may be a few symptom-free days.
- Volhyn fever, also known as five-day fever or trench fever. This leads to sudden headaches, fever and sometimes even meningitis.
Antibiotics are usually a good way to get these infections under control in the case of lice infestation. If left untreated, however, severe courses are possible, which in the worst case can even end fatally.
How do you fight clothes lice?
In order to get rid of clothing lice, unlike head and pubic lice, there is no need for drugs that act directly on the lice. Instead, one takes advantage of the fact that they do not live directly on the body, but on clothing. In the case of a slight lice infestation, it is usually sufficient to change your clothes, bed linen and towels every day and wash them at at least 60 degrees. At this temperature, the lice and eggs are reliably killed.
At temperatures above 60 degrees, an hour is enough to put an end to the lice. If it is delicate laundry that cannot be washed at 60 degrees, it should be disinfected instead.
Furthermore, the parasites can be killed by lack of food or cold. For example, you can close the contaminated textiles in a plastic bag for at least four weeks or put them in a freezer for 24 hours.
There are ointments and creams in the pharmacy against the sometimes severe itching that clothes lice cause.
In the event of an infestation with clothes lice, a doctor should always be consulted and a report should also be made to the responsible health department. Under certain circumstances, an affected accommodation must also be cleaned by a state-approved pest control company, but only in the case of a very strong lice infestation.
Lice infestation: disease course and prognosis
As long as a lice infestation is not specially treated, the parasites can multiply undisturbed. Head lice and pubic lice cannot be impressed by simply washing them or using normal care products. Only the clothes louse can be dealt with by washing clothes.
Even after the first treatment, provided that it was carried out correctly, there is no longer any risk of infection for those affected. And after the second treatment, the lice infestation is usually over.
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