Mosquito bites in Germany are usually just an annoying nuisance. Nevertheless, reports of severe allergic reactions have been accumulating recently. In more southern climes, especially in South America and Africa, serious to fatal diseases can be transmitted by mosquitoes.
What is a mosquito bite?
Infographic on the transmission cycle of malaria by the Anopheles mosquito. Click to enlarge. There are numerous species of mosquitoes that can be found almost all over the globe. Only the polar regions and some deserts are completely free of them. The mosquito bite is carried out exclusively by females, since proteins of the blood are necessary for the fertilized eggs to grow. At the same time, the term “bite” is not quite correct under closer examination. A mosquito has a proboscis to suck blood – it is not a stinger. Instead, they use various mouthparts to suck blood. The main ones used are the stinging bristles, which have two channels inside. Through one, the insect’s saliva is injected into the skin, while the other is used to suck blood. Saliva injection serves several purposes. First, it prevents the host’s blood from clotting so that the blood meal can be sufficiently productive. Second, chemicals are also released into the injection site that first suppress itching. After all, the “victim” should not notice anything about the sting. Subsequently, these very substances lead to swelling and itching due to an intolerance reaction.
Causes
Mosquitoes are capable of transmitting diseases to humans. These include parasitic (malaria, filariasis, and leishmaniasis), viral (yellow fever, dengue fever, and others), and bacterial diseases (tularemia). A disease can only be transmitted if the insect has also been infected via an infested host. The time from ingestion of the pathogens by a mosquito and the possibility of passing them on via saliva is called the extrinsic incubation period. Before this time has elapsed, the infection cannot be passed on to another living being.
Symptoms, complaints, and signs
Overall, the symptoms of a mosquito bite are very clear. A distinction must be made between the normal symptoms of any mosquito bite and the symptoms of an allergic reaction to it. Thus, any mosquito bite can be perceived as a bite, insofar as the affected person is awake. The sensation is similar to that of a small pinprick, but the sting hurts only at the moment of the bite. The puncture site is usually small and quickly begins to itch. However, there is usually no pain, only itching. The itching is also felt after waking up – if the mosquito bite occurred during sleep. The redness of the skin in a mosquito bite is localized. The itching and redness can be intensified by scratching. The same applies to any swelling that has occurred. In case of an allergic reaction to certain substances in the mosquito’s saliva, a more extensive skin reaction may occur. In this case, there is a spreading redness, wheals, severe itching and swelling. These symptoms can vary in severity. In severe cases, there are circulatory problems and corresponding weakness. The injection site itself becomes particularly warm and enormously swollen. In most cases, a hardening – similar to a scar – remains after the symptoms have subsided.
Diagnosis and course
If unusual symptoms occur after a trip to tropical regions, a mosquito-borne disease should always be considered. In the case of malaria, the incubation period can be up to 4 weeks. The symptoms of the Anopheles mosquito-borne infection are similar to influenza. Unlike yellow fever, which becomes noticeable after only 3 to 6 days, in the case of malaria the connection to travel can often no longer be established. Depending on the cause, the different clinical pictures are diagnosed in different ways. The diagnosis of yellow fever is usually made clinically, while in the case of sand fly fever an examination of the blood for antibodies points the way. In skin leishmaniasis, which is caused by parasites of the genus Leishmania, affected individuals show typical skin changes in some forms.A biopsy can support the diagnosis, with boat-shaped leishmania visible in the specimen.
Complications
Mosquito bites usually heal quickly. However, in rare cases, complications may occur. Complications include a severe allergic reaction of the body to the proteins injected by the mosquito during the bite. As with all other insect bites, this can result in huge swellings accompanied by fever or even anaphylactic shock. However, complications are also possible due to the behavior of the stung person. Since a very itchy reddish wheal always forms on the affected area, people often try to relieve the unbearable itch by scratching. This results in skin lesions that can serve as entry points for various bacterial pathogens. Streptococci, for example, can enter the lymphatic system, multiply there and cause lymphedema. If the germs enter the bloodstream, potentially fatal blood poisoning (sepsis) can even develop. It is also dangerous when mosquitoes inject fecal bacteria such as E. coli, which they pick up by sitting on top of animal fecal waste, into the bloodstream when they bite. Mosquitoes as disease vectors of tropical diseases do not yet play a role in Germany. However, travelers to tropical countries should also be vaccinated against tropical pathogens. Otherwise, a mosquito bite there can transmit such diseases as malaria, yellow fever, dengue fever, West Nile fever or chikungunya fever.
When should you go to the doctor?
Normally, a mosquito bite does not require a doctor. With adequate cooling or the use of a mosquito ointment, which can be purchased over-the-counter in drugstores or pharmacies, relief from side effects can be achieved. In addition, the healing process is positively supported by the use of the preparations, as they minimize itching. If people with a weakened immune system or infants suffer a large number of mosquito bites, a doctor should be consulted. If the side effects are so distressing that severe malaise, inner restlessness or tearful behavior persist, the help of a doctor is necessary. If inflammation or open wounds occur, sterile wound care is required. If this cannot be provided to a sufficient extent, a doctor should be consulted, as sepsis is imminent. In case of fever, chills, sweating or pain, a visit to the doctor is also necessary. In case of disturbances of the heart rhythm, severe swelling and an increase in existing complaints, action is required.
Treatment and therapy
Mosquito bites from northern European areas almost never require medical treatment. In some cases, allergic reactions up to anaphylaxis (allergic shock) can be triggered. A doctor should definitely be consulted if corresponding symptoms occur. A sting without complications is treated with small home remedies, such as onion juice or a disinfecting lotion. This minimizes the likelihood of additional infection with bacteria. Despite enormous itching, scratching is not advisable, as the symptoms can be intensified and there is a risk of inflammation. Massive itching can be relieved by a cooling gel, which can also be used for burns and other skin irritations. The more serious communicable diseases are in most cases absolutely in need of treatment, otherwise they can lead to death. Many therapies can only mitigate the course of the disease or boost the immune system to fight the infection. No cure has yet been discovered for malaria. The drug chloroquine is taken for acute attacks. In cases of resistance to chloroquine, doxycycline or atovaquone-proguanil are given for prophylaxis when the risk of malaria is high. Similar treatment is given for yellow fever, dengue fever, leishmaniasis and filariasis. Tularemia, which is often fatal, is treated with antibiotics, with streptomycin being the most effective. Filariasis, which is caused by nematodes from the filarial group, exists in numerous subtypes, some of which are easily treatable. In this case, mosquitoes transmit microfilariae – microscopic threadworms – via their saliva.Treatment is with anthelmintics (medications for worms), with specific medications for adult worms and microfilariae.
Outlook and prognosis
The prognosis for a conventional mosquito bite from a harmless mosquito not carrying pathogens is very good. Within a few days, a mosquito bite usually heals completely. Neither permanent skin changes nor further medical complications are to be expected. Ointments for healing or suitable home remedies can be used, but are not necessary. The prognosis is significantly worse if the puncture site has no chance to heal. This is the case, for example, if there is too much scratching or other skin conditions are present. In such cases, bacterial inflammation can rarely occur, which then leads to a local infection. Further scratching often aggravates this condition. Even with infected mosquito bites, the prognosis is very good if the infection is recognized early and treated quickly. In the case of local infection, healing is possible within a few days and there is no need to worry about permanent damage. The skin regenerates completely. Bites by dangerous mosquitoes, for example in the tropics, on the other hand, can lead to infectious diseases that have a worse prognosis. In the case of malaria, the mortality rate is about 20 percent if untreated, but only two percent if treated. Prompt treatment improves the prognosis. It is true, however, that mosquito bites are considered harmless in central and northern Europe.
Prevention
The best prevention against mosquito bites in general is to wear long-sleeved, dense clothing in problem areas. A repellent spray against mosquitoes or a mosquito net provide relief. With regard to the serious clinical pictures in tropical areas, information before the trip about the contagious diseases there is essential. Vaccinations are available against many of the infections described.
Aftercare
Aftercare for a mosquito bite initially includes treatment of the itching, which may need to be continued. If this reappears after some time, the previously tested therapeutic approaches can be used again. Creams, ointments and gels also soothe the skin and promote rapid healing. Once the itching has subsided completely, no further aftercare measures are usually required. The redness and swelling associated with the sting usually goes away on its own within a few days. However, to rule out possible complications during healing, this process should be observed. In this way, possible infections triggered by the scratching can be detected in time. If the swelling increases or the redness spreads further, a doctor should be consulted. With the help of a blood test, the doctor can clarify whether the mosquito transmitted bacteria or viruses during its bite. Special attention should also be paid to known allergies to insect bites. If such an allergy is present, the treatment initiated in the first step must be continued over a longer period of time after consultation with the responsible physician. Allergic reactions can also occur at a later stage and then require treatment as soon as possible. Allergy sufferers should therefore monitor changes in the skin condition around the sting particularly closely.
What you can do yourself
As a rule, medical care is not necessary for a mosquito bite. Treatment can be carried out by measures that can be performed by yourself. Only in the case of severe allergic reactions – as can occur when coming into contact with insects from tropical regions – consultation with a doctor is recommended. The first measure in the treatment is cooling. This reduces the swelling and at the same time reduces the itching. Itch-relieving lotions and gels can be purchased in pharmacies and drugstores. There are also special products for children, with fewer additives. A tried and tested household remedy is the onion: placing half of it on the stung skin area relieves itching and swelling. The pure juice of aloe vera also has a cooling effect. At the same time, it cares for the irritated skin. A hot spoon on the wound also reduces itching, as the protein of the mosquito venom precipitates due to the heat. However, the most effective is prevention.Mosquito nets on windows and doors, avoidance of stagnant water, avoidance of very strong-smelling perfumes and showering in the morning and evening are recommended, as the smell of sweat attracts mosquitoes. Pharmacies offer numerous sprays and lotions with mosquito-repellent substances. Caution is advised when using for children and allergy sufferers. If in doubt, consult a physician or pharmacist.
