Although mosquitoes are annoying, they are generally considered harmless in this country. Nevertheless, the little pests could possibly transmit dangerous diseases to us. Species like the Asian tiger mosquito are now also native to us. What experts say about this and how to protect yourself from bites.
Everywhere itchy red stitches on the skin – who does not know it. In Germany, mosquito bites are as much a part of summer as ice cream and flip-flops. Even if they can be life-threatening for allergy sufferers, they are usually harmless for everyone else. The greatest danger is scratching the stitches and introducing bacteria into the wound, causing inflammation.
Fortunately, dangerous diseases such as malaria, yellow fever or the Zika virus, which certain mosquito species transmit in Africa, Asia and South America, do not occur here. Even if some species of mosquitoes have been introduced to us from distant countries and have even become native.
According to the Mosquito Atlas , a collaboration between the Leibniz Center for Argraland Research (ZALF) and the Friedrich Loeffler Institute, Federal Research Institute for Animal Health (FLI), five invasive mosquito species have been detected in Germany since 2004:
The latter is now one of the best-known invasive species that has already spread throughout Germany. Specimens were only recently found again in a Berlin allotment garden. This proves that the hibernation was successful and permanent settlement is to be feared, the Senate Department for Health announced. This makes Berlin the northernmost point in Germany where a proliferation of Asian tiger mosquitoes has been proven.
This exotic mosquito species is monitored for occurrence because the animals can transmit over 20 pathogens, such as dengue or chikungunya viruses. “The diseases caused by these viruses have not yet spread in Germany, but the corresponding pathogens are repeatedly brought in by people returning from travel,” the statement continues. According to experts, however, there is currently no health risk from it. According to the Robert Koch Institute, the climatic conditions for the spread of some pathogens are not given here either.
In southern Europe, on the other hand, where extreme temperatures occur over longer periods of time, things are different. In the past, there have already been cases of dengue fever in countries such as Italy and France. The virus is already endemic on the Portuguese island of Madeira. In 2017, there was a chikungunya fever epidemic in Italy related to the Asian tiger mosquito.
But the native mosquito species, of which there are around 50 according to the mosquito atlas, could also pose a risk. For example, some species can transmit rabbit fever. This is a highly infectious zoonosis, which is caused by the bacterium Francisella tularensis and can trigger a variety of symptoms in humans in addition to flu-like symptoms such as fever, chills, headaches and body aches – up to and including severe pneumonia.
According to the Robert Koch Institute, only 20 to 30 cases are reported annually in Germany, but the RKI assumes that the number of unreported cases is significantly higher. It mainly affects people who spend a lot of time outdoors, such as hunters and forest workers.
Infection can occur through contact with infected rodents, consumption of undercooked meat (e.g. rabbit), contaminated water and food. Inhalation of the pathogen through dust and aerosols is also possible, as well as through the bites of ticks, horse flies and mosquitoes. According to the Robert Koch Institute, there is often no evidence of the source of infection.
However, in Sweden in 2019, researchers were able to prove a connection with flood mosquitoes in one of the largest outbreaks of rabbit fever in the country with 979 cases. These mosquitoes also occur in Germany. The extent to which they are involved in rabbit fever infections has not yet been researched.
Mosquitoes could also play a role in the transmission of Lyme disease. So far, ticks have been considered carriers of these bacteria. But people who are diagnosed with Lyme disease often have no memory of a tick bite. Even if the little bloodsuckers often bite into places that are difficult to see, such as skin folds, and are perhaps overlooked and not even noticed.
In fact, the German researcher Sven Klimpel from Goethe University was able to detect Borrelia in ten different mosquitoes in Germany in a study published in 2016. These were mainly pathogens that trigger Lyme disease.
In contrast to rabbit fever, Lyme disease occurs very frequently in Germany. The Robert Koch Institute assumes more than 200,000 cases per year. In 2020, according to figures from the Central Institute for Statutory Health Insurance Physician Care in Germany (Zi), the number of sick people rose by eight percent compared to the previous year. According to the most recent data from 2020, almost 360,000 Lyme diseases nationwide were diagnosed by the panel doctors. So that’s a lot of infections.
According to the Robert Koch Institute, Lyme disease is a “serious disease” that can affect the whole body and affect the skin, nerve tissue, joints and heart function. Facial paralysis can also occur, for example.
It usually makes itself felt first with a reddening that spreads around the tick bite site. Then non-specific flu-like symptoms such as
Symptoms often do not appear until days, weeks or even months after infection. The insidious thing about Borrelia: If left untreated, the pathogens can still cause symptoms years later.
The Robert Koch Institute assumes that the shield tick is responsible for transmission to humans in Central Europe. With her, the Borrelia are in the intestine. At the beginning of the act of sucking, they migrate into the salivary glands and are transmitted to humans with the saliva.
This does not happen immediately, but only a few hours after it has attached itself to the skin. “A transmission by blood-sucking insects has not been documented with certainty so far,” writes the RKI and thus at least does not completely rule out the potential spread by mosquitoes.
With his work, researcher Sven Klimpel was able to detect Borrelia in up to eight percent of the mosquitoes caught at eleven locations in Germany. However, he was unable to show whether these are actually responsible for some of the infections. “There is no reason to panic,” he told the “Ärzteblatt” at the time. “According to our current state of knowledge, mosquitoes are only suitable to a limited extent as carriers of the causative agent of Lyme disease. If anything, they play a rather minor role.
The fact that borrelia could actually be transmitted from mosquitoes to humans does not seem to have been conclusively clarified to this day. “Borrelia bacteria have been detected in isolated cases in outdoor catches of mosquitoes, but that only means that the mosquitoes ingested the Borrelia bacteria together with the blood of the host during a bite,” says mosquito researcher Helge Kampen from the Friedrich Loeffler Institute, Federal Research Institute for Animal Health , at the request of FOCUS Online. According to the mosquito researcher, there is no evidence or evidence of a transmission of Borrelia by mosquitoes, either in the field or in the laboratory.
So even if the risk of contracting a dangerous disease from a mosquito bite seems to be low in this country, you should still protect yourself from the pests. According to Kampen, the best protection is not giving the mosquitoes a chance to reproduce. Standing water, such as bird baths or rain barrels, are the perfect breeding grounds for mosquitoes. Therefore he advises:
If you have been bitten anyway, you should definitely avoid scratching, even if it is difficult. Scratching too hard can lead to bacterial infections and inflammation with significantly more severe symptoms. According to Kampen, it helps the most to cool the puncture site. “Then the whole thing will be over again quickly.”
