They cause itchy wheals on the skin and many people find them annoying: In Germany, the larvae are currently hatching again from the mosquito eggs. “We have good starting conditions,” said Doreen Werner from the Leibniz Center for Agricultural Landscape Research (Zalf) in Müncheberg. The insects like it moist and warm, the biologist explained. How quickly they develop now depends on the weather in spring.
The crucial point is the rain. “We’re having downpours. The question is: will it stay like this? How much is it raining now?” Because mosquitoes like to lay their eggs in puddles, rain barrels or in the damp earth, said the biologist. The larvae need the water and mild temperatures to hatch. “If the puddles don’t last, then the larvae can’t develop either.”
Some mosquitoes are already growing, including forest and meadow mosquitoes – they are somewhat larger and more penetrating than house mosquitoes. This means that their development this year is within the normal time window, explained Werner. Will we face a mosquito plague this summer? “I can’t look into the crystal ball.”
Tiger mosquito becomes native
Because the development depends so much on the weather, forecasts can hardly be made over a longer period of time. It could last around a month or just a week. If it is particularly warm in summer, for example, the mosquitoes only need a week from the time the bloodsucking females lay their eggs until the next generation hatches.
According to the biologist, the Asian tiger mosquito (Aedes albopictus) will also continue to spread in Germany. The exotic mosquito species is originally native to South and Southeast Asia, but is also increasingly found in Central Europe. In Germany it is already buzzing in Bavaria, Baden-Württemberg, Hesse, Thuringia and Berlin.
Werner and her research team can see this using the mosquito atlas. There, mosquitoes are mapped with the help of submissions from the public. The team currently receives 20 to 30 submissions per day.
West Nile fever also in Germany
Exotic mosquito species such as the Asian tiger mosquito or the Japanese bush mosquito have long been known to transmit pathogens such as the Zika, dengue or chikungunya virus. However, various conditions are necessary for the virus to spread.
It has been known for several years that native mosquitoes can also transmit the West Nile fever pathogen. Above all, the eastern federal states and Bavaria are affected and the starting point for the spread, said Werner. According to its own statements, the Robert Koch Institute (RKI) recorded 13 cases of West Nile fever in 2022, which were transmitted by mosquitoes in Germany. In addition, there were four infections without recognizable symptoms, it said on request.
According to the RKI, West Nile fever is usually unremarkable. About every fifth infected person develops a flu-like illness with fever. About one in 100 infected people becomes seriously ill. Experts therefore assume that the number of undetected infections is unreported.
