In Switzerland, three invasive mosquito species have been reported: Aedes albopictus (the Asian tiger mosquito), Aedes japonicus (the East Asian bush mosquito) and Aedes koreicus. All three mosquito species are similar in that they have a the white and-black body coloration in particular on the hind legs. They also breed in small water containers present in the urban area. However, they differ in terms of the level of biting nuisance, potential in transmitting diseases and their geographical distribution in Switzerland.
The Asian tiger mosquito is considered one of the most invasive species globally. Originally from Southeast Asia, the mosquito has colonised the world in just a few decades thanks to human activities, such as the passive transport by vehicles and the trade of used tyres, and its marked ecological
adaptability. It is currently present throughout southern Europe and is advancing north (see European distribution map).
In addition to Asian tiger mosquito’s biting nuisance, the mosquito is of public health concern it can potentially transmit infectious diseases such as dengue and chikungunya even in Switzerland from a travellers returning from endemic areas to other people.
Although it is virtually impossible to prevent the mosquito’s expansion the aim is to keep population densities as low as possible through a coordinated effort among cantonal and national authorities, and with the help of the public.
citizens: therefore, learn the simple measures to be taken to limit its presence and send us your reports of suspicious cases.
The Asian tiger mosquito resembles the well-known house mosquito both in shape and size, yet it has a black coloration with clearly visible white patterns on the body and the legs. It has also a clear white stripe running across the back.
Knowing the tiger mosquito will help to fighting it:
Life cycle. After mating, the female mosquito needs a blood meal to complete the development of its eggs. Aquatic phase. The tiger mosquito glues its eggs on a solid surface just above the water surface line. Once the water level raises the eggs will hatch. Before the newly hatched larvae reach the pupal stage they undergo four larval stages and one pupal stage. From the pupa new adults emerge and the aerial phase begins again. During the summer the aquatic phase usually lasts one week. The adults, resting in the shade on the vegetation, live about a month and may several deposit eggs multiple times. All mosquitoes need still water. Rivers are therefore not places of mosquito production.
Nuisance. The female bites during the day and may take repeatedly a blood meal from both humans and animals.
The Asian tiger mosquito colonises a small amount of water. Various containers (e.g. saucepans, drums, catch basins, holes in the walls, etc.) (information leaflet) that contain water for over a week can produce tiger mosquitoes. The species does not like large quantities of water in open spaces, so it is not found in ponds, flooded roofs or unattended pools, while it may colonise underground cisterns or shady pools.
The mosquito’s strategy to overwinter. Eggs can survive dry conditions for longer periods of
time. Eggs laid in late summer can easily withstand winter temperatures and then hatch in the following spring. Another strategy to overcome the winter, as frequently observed in the Canton of Ticino, are quiescent adults inside homes.
Exponential growth. A female lays about 60 eggs, half of which will produce females. Without prompt intervention a single female may produce thousands if not millions offspring on one summer. At our latitudes, the first mosquitoes appear mid-April, the highest densities are then reached in mid-August and towards the end of September the mosquitoes become inactive, either as dormant eggs or quiescent adults. Depending on the weather conditions mosquitoes might still be active seasonal until November.
Urban. At our latitudes, the Asian tiger mosquito is almost exclusively urban, where it finds abundant
sites of reproduction.
Short flight ranges. The adult mosquito is assumed to fly only a few meters from the breeding site and, therefore, the breeding sites are usually near the place you are bitten.
Potential disease vector. As a female takes multiple blood meals it may carry pathogens from an infected to a non-infected person. However, not all mosquitoes can transmit diseases but the Asian tiger is known to be competent to transmit dengue, chikungunya and Zkia viruses, and dirofilaria (heartworm). The above viral diseases are all notifiable and closely monitored in Switzerland.
Everyone is encouraged to take care of their own property, while the cantons take care of the public areas. The tiger mosquito can be effectively controlled in your surrounding through the prevention of larval breeding by removing standing water and by treating those containers that cannot be removed (leaflet).
Distribution in Switzerland
The tiger mosquito has first been established along the valley bottoms in the canton of Ticino and the Italian part of the Canton of Grisons, and a first population might also be present in Basel-Stadt. The mosquito has been reported from Zurich and from several service areas along the A2 motorway.
The Asian bush mosquito is another invasive species. Aedes japonicus, endemic to Japan and Korea, has reached North America and Europe through the trade of used tyres. The mosquito is rapidly colonising large areas of central Europe (see European distribution map) both through passive transport (vehicles, used tyres trade), and through active dispersal. The species prefers colder temperatures as compared to the tiger mosquito. The bush mosquito mainly bites in close proximity to woodlands and so far no disease cases have been associated to this species in Europe. In urban areas, the measures taken against the tiger mosquito are expected to also work against the Asian bush mosquito.
The species is often confused with the tiger mosquito due to the visible white and-black patterns on the legs and body. Usually, the Asian bush mosquito is slightly larger in size than the tiger mosquito and does not have a clear white line that runs across the back, instead it is characterised by five, five slightly yellowish lines.
The life cycle of Aedes japonicus is similar to that of the tiger mosquito (Aedes albopictus). The Asian bush mosquito prefers also small water containers, produces eggs that are resistant to dessiccation and cold winters, and bites mainly during the day. However, adults are more active in cooler areas such as the edges of the forest. It seems that adults move quickly along green corridors, allowing this species to colonise large regions within few years.
Aedes japonicus is not considered an important disease vector. In the United States, it is considered, together with other species, a vector of the West Nile virus and its competence for dengue and chikungunya viruses has been demonstrated in the laboratory.
In urban areas the same prevention measures adopted as against the tiger mosquito work against Aedes japonicus.
Distribution in Switzerland
Aedes japonicus was first found in the Canton of Aagau in 2008. Since then it has rapidly spread into Germany and neighboring cantons. Since 2012 the Asian bush mosquito is also found south the Alps and continues to actively spread in all directions.
Originally from Korea, as suggested by its name, Aedes koreicus is also an invasive species that has managed to reach Europe through human activities (probably the trade of used tyres). The species is not yet widespread in Europe, but has been reported from northern Italy, Switzerland, Belgium and Russia (see European distribution map). As the Asian bush mosquito, Aedes koreicus prefers a more temperate climates but prefers more urban habitats, much alike the Asian tiger mosquito. So far Aedes koreicus has not been implicated as a carrier of human diseases.
In urban areas control measures taken against the tiger mosquito may also work against Aedes koreicus.
Aedes koreicus is often confused with the Asian tiger mosquito due to the visible white and-black patterns on the legs and on the body. Its size corresponds to that of the tiger mosquito, but it does not have a clear white line that runs through the thorax.
The life cycle of Aedes koreicus is similar to that of the Asian tiger mosquito (Aedes albopictus) in that this species also prefers small water containers for breeding, produces desiccation resistant eggs may also survive cold winters, the females bite during the day.
Aedes koreicus is not considered a vector of human diseases.
Distribution in Switzerland
Aedes koreicus has been found for the first time in the Canton of Ticino in 2012, in the Italian speaking part of Grisons in 2017 and along the Swiss motorways in 2016. In Switzerland this mosquito species is currently present only at low densities, living in urban environments.