Austria: Asia-endemic mosquitoes continue to spread

According to a study, several species of Asia-endemic mosquitoes are spreading in Tyrol. This increases the transmission risk of dangerous viruses such as Dengue, Chikungunya, and Zika.

Monitoring of mosquito species is of importance to public health systems worldwide

Around 50 species of mosquitoes are known in Austria - and new potentially invasive species are being added, as a study just presented by the University of Veterinary Medicine, Vienna (German: Vetmeduni Vienna) shows. According to the study, several species of Asia-endemic mosquitoes are spreading in Tyrol. This also increases the transmission risk of dangerous viruses such as Dengue, Chikungunya, and Zika. The researchers recommend monitoring the mosquito fauna in European regions.

The key findings of the study are not very encouraging: There are initial signs that the Asian tiger mosquito (Aedes albopictus) is settling down in Austrian regions, i.e. is hibernating in Tyrol and is not being reintroduced every year. The Japanese bush mosquito (Aedes japonicus) is now native to Tyrol, as it is in all other provinces of Austria. In addition, the researchers succeeded in detecting another species of mosquito for the first time in Austria: the Korean Bush Mosquito (Aedes koreicus).

Main study author Hans-Peter Führer from the Institute of Parasitology at Vetmeduni Vienna comments: "The detection of the Asian tiger mosquito, the Japanese bush mosquito, and the Korean bush mosquito is of great importance for the human population, for public health and for the relevant policy decision-makers. Asian tiger mosquitoes, in particular, can transmit dangerous pathogens such as dengue, chikungunya, and zika while native mosquitoes are not able to do so. In addition, the new species of mosquitoes have some more unpleasant side effects, they can occur in large masses and also bite during the day".

Frequent distribution along motorways, and now, also in cities

The researchers investigated the spread of the mosquitoes using so-called ovitraps, a device on which the mosquitoes lay their eggs. As part of the scientific mosquito monitoring program, Ovitraps were placed weekly at 67 locations from May to October 2018 (17 in East Tyrol and 50 in North Tyrol, Austria). Samples were taken on motorways, urban, and rural areas.

The prevalence of new arrivals is already quite high: eggs of non-native mosquitoes were found at 18 of 67 sites (27%). Both the Asian tiger mosquito and the Japanese bush mosquito were documented on motorways and in urban areas in East and North Tyrol. The Korean bush mosquito was also found for the first time in East Tyrol.

Hans-Peter Führer proposes an explanation for their frequent detection on motorways: "Alien species of mosquitoes are mainly introduced through the transfer of goods, but they can also simply travel on the car. Therefore, motorways are the most important entry points for invasive mosquito species. The Asian tiger mosquito was already found along the Inn river valley motorway in earlier years. New, however, is the repeated evidence in urban areas, specifically in Innsbruck, Kufstein, and Lienz".

Further surveillance is important for public health

Mosquitoes (Culicidae family, of which there are about 3,500 species worldwide) are of great importance for human and animal health because of their ability to transmit various pathogens. In Europe, mosquitoes have become increasingly important for public health in recent years with the establishment of non-endemic mosquitoes of the genus Aedes. The tiger mosquito has already caused local transmissions of the potentially life-threatening viral diseases such as dengue and chikungunya, for example in France and Italy. "Based on our results, continuous monitoring of the new mosquito species is urgently required," concluded Führer.