Austrian gnat monitoring programme by AGES

In Austria, little used to be known about the spread and prevalence of exotic mosquitoes associated with climate change. For this reason, AGES set up a gnat monitoring programme to control vectors (carriers) of human viral pathogens such as the West Nile (WVN), Dengue and Chikungunya viruses. Furthermore, the vectors found are, in cooperation with the University for Veterinary Medicine Vienna, also tested for bacterial infections spread by mosquitoes such as tularemia (“rabbit fever”) and for parasitic diseases such as leishmaniosis transmitted by sand flies. Through the programme, mosquitoes are collected and classified at predefined locations. Using biomolecular methods, the level of endemic infection of the gnat populations with the above-mentioned pathogens is then systematically determined. Due to the mosquitoes found and the potential detection of human viral pathogens, data is now available providing information on the risk of transmission, thus possibly enabling further systematic investigation measures.

In all nine federal states, gnats are being caught, by means of special traps, so far at 37 selected locations in cultivated land (i.e. land used for agricultural purposes). The target quantity is about 5,000 mosquitoes per year. Special attention is paid to the search for the species Aedes japonicus (Asian bush mosquito) and Aedes albopictus (Asian tiger mosquito). All over Austria, the trap locations have largely been chosen in the typical mosquito habitats, i.e. along rivers and lakes:

• in the east along the Danube, March and Thaya and in the Neusiedler Lake area
• in the south along the Mur and Drau and in the border region with Slovenia
• in the west, in lake areas and in elevated regions

The above map shows, by federal state, the gnat types that have been caught as part of the monitoring programme.

In Austria, there are currently about 40 different types of gnats of six different genera – see types of life forms of mosquitoes.

In August 2011, Aedes (Ochlerotatus) japonicus japonicus was detected in Austria (southern Styria) for the first time. In the same year, the West Nile virus was found in a single sample of a domestic type of house mosquito (Culex pipiens). The sample had been collected in Lower Austria (St. Pölten Land District).

The individual species of the mosquitoes caught is determined. Thereafter, the mosquitoes are tested for West Nile (WNV) and other strains of viruses by means of PCR analysis. Where required, the virus type can be established as well by means of nucleic acid sequencing. The number of gnat traps will, in cooperation with the federal state authorities and the Federal Ministry of Health, be further optimised in order to fine-tune the monitoring measures.
It must be emphasised that especially the West Nile Virus can be transmitted by an unusually large number of mosquitoes (43 species in North America alone). The genera Culex and Aedes (=Ochlerotatus) in particular are regarded as possible vectors. They were also found as part of the gnat monitoring programme of the AGES. See also: vectors.