Tiger mosquito also transmits the tropical Chikungunya virus in this country
What has been suspected recently has now been scientifically proven for the first time: Introduced tiger mosquitoes can spread diseases in this country that previously only occurred in tropical regions. Researchers showed that the tiger mosquito is also able to spread the tropical Chikungunya virus at lower temperatures in this country. Such a virus infection can cause severe, debilitating and often chronic joint pain.
In the experiments carried out in the high-security insectarium of the Bernhard Nocht Institute for Tropical Medicine (BNITM), a team of researchers has demonstrated that the Asian tiger mosquito can also spread tropical Chikungunya viruses in Germany at relatively mild temperatures of around 18 degrees Celsius. It is therefore likely that the virus will spread to German regions if the tiger mosquito population continues to increase. The research results were recently published in the specialist journal "Eurosurveillance".
Chikungunya virus can spread in Germany
Contrary to many other tropical viruses, the Chikungunya virus is also active at the usual moderate temperatures. In other European countries, such as Italy and France, outbreaks were confirmed by the authorities in 2017. The BNITM scientists showed that such outbreaks are also possible in Germany.
Temperate temperatures of 18 degrees Celsius are sufficient
In the laboratory, the BNITM researchers kept viral Aedes albopictus mosquitoes from Germany and Italy in climate chambers with average temperatures of 18, 21 or 24 degrees for two weeks. "The virus was able to reproduce very well in mosquitoes from the German population even at a temperature of 18 degrees," reports Professor Egbert Tannich, head of the National Reference Center for Tropical Infectious Agents at the BNITM in a press release. After two weeks, infectious viruses were found in saliva in over 50 percent of the animals, the expert said.
The population is crucial
According to Tannich, it has been proven that the spread of the Chikungunya virus is determined less by the outside temperature than by the presence of the mosquito. "The risk of Chikungunya virus transmission to people in Germany can currently be assessed as low," explains the professor. The tiger mosquito is currently only locally limited and can be found in small numbers in Germany. In addition, the virus must first get into the wild mosquito population.
Tiger mosquito native to 25 European countries
The two mosquitoes Aedes aegypti and Aedes albopictus, known as tiger mosquitoes, are considered the most important transmitters for the Chikungunya virus. Aedes albopictus is native to and around Germany, for example in Italy and along the upper Rhine plain in Germany and France. According to the Bernhard Nocht Institute, this type of mosquito has already settled in over 25 European countries.
Caution is advised
Tannich and his colleagues strongly recommend that a suitable system for mosquito surveillance and control be established in all European countries with established Aedes albopictus populations. A further spread of the tiger mosquito can be prevented by reduction or elimination, the insect experts sum up.
Can other tropical diseases also spread here?
According to the BNITM researchers, the presence of viruses in a mosquito alone is not sufficient for transmission. Two events have to occur here: First, a tiger mosquito in Germany has to bite a person who has tropical viruses in their blood. Second, the mosquito should actually be able to multiply and transmit the virus. With 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
BNITM experts currently see a low risk of spreading other tropical pathogens such as Zika, Dengue or West Nile viruses that trigger severe tropical diseases, since these viruses only multiply at very warm temperatures that last for several weeks . "As a rule, we do not find these conditions of an average of 25 to 27 degrees here in Germany," concludes Tannich.
The professor sees a natural double control against Zika, Dengue and West Nile viruses. On the one hand, these tropical viruses would be inhibited by the prevailing temperatures and, on the other hand, the number of carriers would be very low. (vb)