Müncheberg (dpa) – buzzing, small scoop, then itching often for days – with spring-like weather, mosquitoes are on the move again.
Usually this is only annoying, in rare cases mosquito bites can also make you sick: it has been known for several years that domestic mosquitoes can transmit the pathogens that cause West Nile fever. Besides Bavaria, the East is a hot spot for distribution. “We don’t know why yet,” Doreen Werner, a biologist at the Leibniz Agricultural Landscape Research Center (SALF) in Mönchberg (Märkesch-Oderland) told DPA. Thuringia, Saxony-Anhalt, Saxony and Brandenburg were affected.
West Nile virus originally occurs in warmer regions of the world. However, scientists from the Friedrich Loeffler Institute (FLI) have already identified domestic mosquitoes as carriers of the pathogen. The virus can spend the winter in mosquitoes. “The higher the temperature, the better pathogens can develop,” Werner explains. According to the Robert Koch Institute (RKI), infection usually goes unnoticed at all, and some infected people experience flu-like symptoms. Therefore, severe episodes of West Nile fever are rare but potentially fatal. According to the RKI, human cases of infection have been recorded in Germany since 2019. It is expected that the pathogen will continue to establish itself in Germany.
Climate change also plays a role in the spread of viruses through mosquitoes. Werner estimates that “climate change means that pathogens in mosquitoes can reproduce better. However, the main focus is increasing globalization.” For example, exotic mosquito species can be spread from one continent to another by trade in goods, such as the Asian tiger mosquito with the global trade in used tyres. The mosquito expert explains that the eggs were traveling in tires as stowaways. When it is moistened with water, the larvae hatch. Good development opportunities in the destination may lead to stability. But Werner also cites camping tourism from southern Europe as a possible way to spread the word.
Exotic mosquito species such as the Asian tiger mosquito or the Japanese bush mosquito have long been known to transmit pathogens such as Zika virus, dengue fever or chikungunya. In Zalf, scientists are looking into the prevalence of mosquitoes introduced into Germany and the question of whether they can also transmit pathogens in that country. In order for that to happen, for example, for a tiger mosquito to spread the pathogen of a tropical disease, it first has to come into contact with infected travelers returning from travel, Werner explains. To do this, the mosquito and the virus must be compatible – the virus must be able to develop further in mosquitoes.
Mosquitoes have antifreeze inside.
The expert says the probability is low, but it is no longer zero. Residents need to be informed, and they can support the science, too: The institutes are calling for mosquitoes to be sent to the leopard to research its spread. There the species is identified and entered into the Mosquito Atlas.
Werner explained that more than 50 different species of mosquitoes in Germany have different strategies for getting through the cold season. They usually hibernate as eggs or larvae, or survive the winter as adults in damp cellars or in warm buildings – eg when they perch near firewood. “The colder the winter, the better for mosquitoes,” says the researcher. Mosquitoes have built-in antifreeze.
According to the expert, when temperatures fluctuate around 0 degrees, insects consume a lot of energy because they have to constantly freeze and thaw again. Then hungry a lot. In addition, fungal spores are also active at 0 degrees, which overgrowth of mosquitoes. No matter how many or how few survive the winter – spring weather conditions are crucial. With mild temperatures, mosquitoes lay their eggs relatively early this year, for example in rain barrels and small pools of water.
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