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It is only half a centimeter tall, yet the tiger mosquito is a dreaded animal: in the tropics and subtropics, where it is warm and humid, it transmits dangerous infectious diseases such as Chikungunya, Dengue, or West Nile fever. The Asian tiger mosquito (Aedes albopticus) is also particularly aggressive, stinging not only at dusk, but also during the day. In Germany, the mosquito was not a major threat so far, because for their larvae it is usually simply too cold in this country.
But the mosquito is on the rise in Europe. In 2007, 200 people in northern Italy fell ill with chikungunya fever. The virus had been introduced by a traveler, the now occurring throughout Italy Asian tiger mosquito had then spread the virus.
Nearly ten years ago, insect researchers also found eggs of the mosquito in Germany - on a motorway parking lot on the Upper Rhine. In the meantime, tiger mosquito populations have been detected in various regions of Germany. For example, in Heidelberg, Freiburg - and in Jena: The Unistadt in Thuringia is the world's northernmost point, where ever a tiger mosquito people was found.
There are three reasons why the tiger mosquito continues to spread northward: climate change, tourism and global retail chains.
Climate change: why the mosquito feels good in the north
The tiger mosquito has adapted to the climate in temperate latitudes, the larvae can now survive the winter in this country. This has been proven by the Friedrich-Loeffler-Institut (FLI) in several studies. For this purpose, the researchers exposed Aedes mosquito larvae in plastic boxes on the Baltic island of Riems during the winter. The larvae survived and slipped on in the spring. In addition to their adaptability, the mosquitoes are especially affected by climate change: the average annual temperature in Germany has risen by 1.5 degrees since 1881, and winters are on average even 1.6 degrees warmer.
Scientists from the University of Florida have calculated how the mosquito could spread in the future due to climate change. Their prognosis: The mosquito will increasingly feel at home in northern latitudes and could also become a significant transmitter of diseases there - of diseases that can be very dangerous for humans.
In addition: At higher temperatures, one or the other domestic mosquito species may prove to be an efficient carrier for such diseases. "This has never been investigated because the problem was not there before," says mosquito researcher Helge Kampen from the FLI, who has been involved in the spread of the species for years. The scientists, he says, were just beginning to study it.
The US research team led by Sadie J. Ryan has based his study on various climate scenarios. In the worst case scenario, namely that greenhouse gas emissions continue to rise and cause a global temperature increase of around 4 degrees Celsius, Germany could also have optimal conditions for the mosquito for several months a year.
As with most mosquitoes suck also with the Asian tiger mosquito only the females blood. The protein they contain is needed for egg production. Mild temperatures between 20 and 30 degrees favor propagation: the warmer, the more often the female mosquitoes lay eggs - and the more often they sting. In warm months, the risk of infection increases:
The clutch can not be damaged by particularly severe winters: Many tiger-gland females look for storage areas that are protected throughout the year. They lay their eggs, for example, in the sewers, where it is warm even in the winter months.
On the other hand, in other parts of the world, the mosquito could become overheated in the long run in the face of global warming. In Southeast Asia, Africa or the Amazon Basin, where it was formerly home, its presence could even decline.
Tourism and trade: How the mosquito comes to Germany
The mosquito does not get far out of its own power. "She flies badly and reluctantly," says researcher Kampen. In a globalized world, however, the tiger mosquito does not have to make an effort: it travels as a stowaway - in containers, in cars, in its luggage.
A gateway to Europe, for example, is the tire trade: by boat, old tires from tiger-ridden areas in Asia come to Europe to be shredded and used as fuel or for road construction. The tiger mosquito travels as a stowaway with the tires. Small puddles of water on the rubber are ideal breeding grounds for their eggs and larvae.
On European soil, the Asian tiger mosquito first appeared in Albania in 1979, ten years later in the Italian port of Genoa. It is now widespread throughout Italy. From there, the mosquito crosses the Alps as a traveling companion, for example in the luggage of German tourists. When the suitcases are opened in Germany, the mosquito hums into its new habitat.
The mosquito is here - are now the infectious diseases?
"The mosquito alone is not a danger," says Hendrik Wilking of the Robert Koch Institute. Because it does not automatically carry pathogens in itself. The cycle of infection goes like this: A mosquito stings a person infected, for example, on vacation, through whose blood she absorbs the pathogen. At the next stitch, she releases the pathogen into the blood of the next person. Any other mosquito that takes in that person's blood carries the virus - and could spread diseases like chikungungya, dengue fever, or zika in germany.
James Gathany / Centers for Disease Control / REUTERS
This is how the tiger mosquito looks: half a centimeter long, jet black with white spots on body and legs
In Saxony, a 70-year-old has recently been infected by a mosquito bite with the West Nile virus. The transmission was very likely in the case of mosquito bites first of birds and subsequently the human. Birds are the main hosts of the virus. Mosquitoes often become infected when they sting the animals and can then pass on the pathogen to humans.
The likelihood of an epidemic remains low in Germany. The medical care in this country is good - should somebody get infected with an infectious disease. In addition, the spread of mosquitoes and pathogens is also a hygiene issue: the cleaner, for example, the sanitary facilities, the less suitable breeding sites find the mosquitoes. The draining of swamps also helps to slow down mosquito repellence. In general: water buckets and rain barrels in the garden are popular breeding grounds for mosquitoes of all kinds. Anyone who wants to stem their multiplication should empty the water every 10 days at the latest.
Anyone who finds a mosquito at home that seems unknown to him, can send it to the operators of the mosquito Atlas. The Mosquito Atlas maps the mosquitoes in Germany and maps where mosquitoes occur. There, the copies are examined, which were previously submitted by private individuals. For example, if a tiger mosquito is present, the FLI mosquito task force intervenes: The researchers drive to the place where the tiger mosquito appeared and try to find the breeding site. Then they inform appropriate health authorities that can take action to combat it. However, the scientists can not intervene. After all, according to the "Infection Protection Act", the federal states are only obliged to fight the species when an illness breaks out.
Researchers agree that one should prepare for outbreaks of tropical diseases - and not delay in combating them. This also means, according to mosquito researcher Kampen, to fight the tiger mosquito in Germany as soon as it is discovered. "If you just let it run like that," he says, "at some point we'll have such a big tiger mosquito population here that we'll have no chance against them."
This article is part of the project Global Society, for which our reporters report from four continents. The project is long-term and supported by the Bill & Melinda Gates Foundation.
What is the project Global Society?
Under the title Global Society, reporters from Asia, Africa, Latin America and Europe will be reporting on injustices in a globalized world, socio-political challenges and sustainable development. The reportages, analyzes, photo galleries, videos and podcasts appear in the Politics Department of SPIEGEL. The project is long-term and will be supported over three years by the Bill & Melinda Gates Foundation (BMGF).
Are the journalistic contents independent of the foundation?
Yes. The editorial content is created without the influence of the Gates Foundation.
Do other media have similar projects?
Yes. Major European media such as "The Guardian" and "El País" have created similar sections on their news pages with "Global Development" or "Planeta Futuro" with the support of the Gates Foundation.
Was there already similar projects at SPIEGEL ONLINE?
SPIEGEL ONLINE has already implemented two projects in recent years with the European Journalism Center (EJC) and the support of the Bill & Melinda Gates Foundation: The "Expedition The Day After tomorrow" on Global Sustainability Goals and the journalistic refugee project "The New Arrivals" Several award-winning multimedia reports on the topics of migration and escape have emerged.
Where can I find all the publications on the Global Society?
The pieces can be found at SPIEGEL ONLINE on the topic page Global Society.
