New health risk Migrant tiger mosquitoes Exposure to severe infectious diseases

Tigermuck transmits the tropical Chikungunya virus here in Germany too

What has recently been suggested again and again has now been scientifically proven for the first time: entrained tiger mosquitoes can spread diseases in Germany that previously only occurred in tropical regions. Researchers showed that the tiger mosquito in this country is able to spread the tropical Chikungunya virus at lower temperatures. Such a viral infection can cause severe, debilitating and often chronic joint pain.

In the high-security insectarium of the Bernhard Nocht Institute for Tropical Medicine (BNITM), a research team has demonstrated in experiments conducted that the Asian tiger mosquito in Germany can spread tropical Chikungunya viruses at relatively mild temperatures of around 18 degrees Celsius. Thus, a spread of viruses is also likely in German regions, if the tiger mosquito population continues to increase. The research results were recently published in the journal "Eurosurveillance".

There has been much speculation lately about whether tropical diseases can spread in Germany. Now a research team has shown that tropical Chikungunya viruses can spread even at temperate temperatures around 18 degrees Celsius. (Image: nechaevkon / fotolia.com)

Chikungunya virus can spread in Germany

Contrary to many other tropical viruses, the Chikungunya virus is also active at the temperate temperatures used here. In other European countries, such as Italy and France, outbreaks have already been confirmed by the authorities in 2017. The BNITM scientists showed that such outbreaks are also possible in Germany.

Moderate temperatures of 18 degrees Celsius are sufficient

In the laboratory, the BNITM researchers kept viral Aedes albopictus mosquitoes from Germany and Italy in climatic chambers with average temperatures of 18, 21 or 24 degrees for two weeks. "In mosquitoes from the German population, the virus was able to multiply very well even at a temperature of 18 degrees," said Professor Egbert Tannich, director of the National Reference Center for Tropical Infectious Diseases at BNITM in a press release. After two weeks, more than 50 percent of the animals had been found to have infectious viruses in their saliva, according to the expert.

The population is crucial

According to Tannich, it is thus proved that the distribution of Chikungunya virus is determined less by the outside temperature but primarily by the occurrence of the carrier mosquito. "Currently, the risk of Chikungunya virus transmission to humans in Germany is estimated to be low," explains the professor. The tiger mosquito is at present only locally limited and to find in small number in Germany. In addition, the virus must first reach the free-living mosquito population.

Tiger mosquito native in 25 European countries

The two mosquitoes Aedes aegypti and Aedes albopictus, known as tiger mosquitoes, are considered the most important transmitters of the Chikungunya virus. In and around Germany, for example, Aedes albopictus is native to Italy and along the upper Rhine plain in Germany and France. According to the Bernhard Nocht Institute, this mosquito species has already settled in over 25 European countries.

Caution is advised

Tannich and his colleagues strongly recommend establishing an appropriate mosquito control and control system in all European countries with established Aedes albopictus populations. A further spread of the tiger mosquito can be prevented by reduction or elimination, summon the insect experts.

Can other tropical diseases also spread here?

According to the BNITM researchers, the presence of viruses in a mosquito alone is insufficient for transmission. Two events have to occur here: First, a tiger mosquito in Germany has to sting a person who has tropical viruses in their blood. Second, the mosquito should actually be able to multiply and transmit the virus. For most tropical viruses, this is usually only possible at outside temperatures of over 25 degrees Celsius over a period of several weeks.

Preliminary all-clear for Zika, Dengue and West Nile viruses

For other tropical pathogens, such as Zika, Dengue and West Nile viruses, which cause serious tropical diseases, BNITM experts currently see a low risk of spreading, as these viruses only multiply in very warm temperatures that persist for several weeks , "These conditions of an average of 25 to 27 degrees are generally not found here in Germany," Tannich concludes.

Double control

Against Zika, Dengue and West Nile viruses the professor sees a natural double control. On the one hand, these tropical viruses are inhibited by the prevailing temperatures and, on the other hand, the occurrence of the carriers is very low. (Vb)