New mosquito species found in Finland

A mosquito species that had not previously been recorded in Finland was discovered in the coastal municipality of Pori.

According to the study conducted by the University of Helsinki, the Culex modestus became the 44th species of mosquito found in the country and the northernmost record of the species in Europe. Previous finds closer to Finland, but further south, have been made in Leningrad Province, Russia, and Skåne, Sweden.

The new species was found by researcher Lorna Culverwell, from the university’s Department of Virology, among mosquito samples collected in the summer of 2022 in coastal areas of Finland. One male specimen was identified after examination of the genitalia and DNA analysis. The results of the study were published in preprint format, not yet peer reviewed, in the Journal of the European Mosquito Control Association.

“Only one specimen of this species has been found, but I believe it is unlikely to be the only one of its kind in Finland,” says Lorna, in a statement.

risk of infection in finland

The identification of a new species of mosquito in a territory is a cause for concern about the potential for disease transmission. the species Culex modestus is known to transmit West Nile virus, a flavivirus, in southern Europe between birds and humans or birds and horses.

In most human cases, West Nile virus causes a mild infection with symptoms such as fever, headache, and muscle aches. In some cases, the infection can cause neurological disorders. However, to date, West Nile virus has not been discovered in Finland, according to the study.

“The Finns shouldn’t be worried about the discovery of the mosquito at this point. To date, no infections acquired in Finland have been discovered in humans or horses, but this discovery is a reminder that we must be aware of which species of mosquitoes are here. Knowing possible mosquito-borne diseases to which these species are linked in other parts of the world helps us to better investigate the likelihood of these infections occurring in the future,” says the scientist.

Impacts of warmer weather

Mosquitoes of the genus Culex can harbor West Nile virus in bird populations, including the species Culex pipiens It is Culex modestus.

Transmission to humans requires that a mosquito has bitten an infected bird, for example, and that the virus has reached the insect’s saliva. After the bite, a human can contract and infection.

“At present, transmission of the virus to humans or horses is very unlikely, as multiple species are required for a disease transmission cycle to occur. First, it would be necessary for West Nile virus to already be present in local or migratory birds in Finland. No viruses have been reported so far, despite small-scale screening of birds in some locations in Finland. Second, only one specimen of Culex modestus is so far known from a location in Finland. For transmission to occur, a greater number of mosquitoes would be needed for the possibility of some of them finding any infected bird and surviving to bite humans or horses several days later”, says the expert.