Tiger mosquito on the increase.
Text: Reto Caluori
At first, the spread of the Asian tiger mosquito was limited to Ticino. Now, however, it is colonizing more and more new regions in Switzerland. The Asian tiger mosquito (Aedes albopictus) is an invasive mosquito species that originates from Southeast Asia. It has adapted perfectly to its new environment and is starting to establish itself here.
This striped mosquito poses a problem, as it bites even during the day and can transmit tropical diseases. Although the latter has not yet happened in Switzerland, it is reason enough to monitor and control the mosquito’s spread.
The current populations are offspring from individuals that were introduced into Italy from the USA in 1990s. In Europe, the tiger mosquito has primarily been transported passively in vehicles along the main traffic axes and has come to colonize large parts of the Mediterranean basin, even crossing the Alps. In 2015, its presence was also confirmed in Basel.
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To give them an idea of the prevalence and distribution of the tiger mosquito, the researchers place containers with water in which the female mosquitos lay their eggs. Each trap contains a strip of wood sticking out of the water for eggs to be deposited on. (Image: University of Basel, Christian Flierl)link.zoom -
The containers are collected every two weeks. On the pieces of wood, there are now rows of dark eggs that were laid on the water surface at different times. (Image: University of Basel, Christian Flierl)link.zoom -
Potential breeding grounds are located along transport routes, which play a key role in the spread of the tiger mosquito. Since the Basel region is a hub for international goods transport by road and rail, researchers like Martin Gschwind and Freya Pappert from the Swiss TPH (pictured here) monitor these locations very closely. (Image: University of Basel, Christian Flierl)link.zoom -
Monitoring also includes collecting and checking citizen reports. The researchers examine letters and photos to determine whether the insects in question are indeed tiger mosquitos. (Image: University of Basel, Christian Flierl)link.zoom -
Head of research Dr. Pie Müller identifies a tiger mosquito using a stereo microscope. The black-and-white patterns on its body and legs are clearly visible. (Image: University of Basel, Christian Flierl)link.zoom -
In the laboratory, the eggs on the wooden strips are also counted. Using mass spectrometry, it is possible to determine whether the eggs come from a tiger mosquito. (Image: University of Basel, Christian Flierl)link.zoom
Since then, researchers from the Swiss Tropical and Public Health Institute (Swiss TPH) have been monitoring its spread in the region. “We have found tiger mosquitos in various locations,” says Dr. Pie Muller, who leads the monitoring project. DNA analyses will show whether these are newly introduced individuals or come from populations that have overwintered here.
Although it’s unlikely that the tiger mosquito will be prevented from gaining a foothold, the researchers’ aim is to keep the populations as small as possible. To this end, they are studying aspects of the mosquitos’ behavior, such as their flying abilities. This will make it possible to estimate how far the insects are able to spread without the aid of transportation.
Pie Müller is a research group leader at the Swiss TPH and a lecturer at the University of Basel. His main research interest is the biology of mosquitos, and developing and implementing new methods of surveillance and control. He is the Swiss principal investigator for TIGER, a trinational network that surveys the Asian tiger mosquito in the Upper Rhine region.
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