Warm summer, more mosquitoes

Warmer summers and changes in precipitation bring more mosquitoes and more exotic infectious diseases. This is the simplified scenario that can be expected as a result of climate change. On the occasion of today's World Mosquito Day, researchers from the Bernhard Nocht Institute for Tropical Medicine (BNITM) are therefore calling for CO2 emissions to be reduced and mosquito control to be intensified.

Climate change promotes outbreaks of mosquito-borne pathogens in two ways. Firstly, exotic mosquito species are spreading further and further north. The Asian tiger mosquito Aedes albopictus, for example, has been native to southern Europe since the 1990s. There, it is particularly responsible for outbreaks of the Chikungunya virus and the Dengue virus. In Germany, Aedes albopictus populations have also become established.

On the other hand, there is the correlation: the higher the midsummer temperatures, the faster many arboviruses multiply in mosquitoes. And the higher the risk that mosquitoes can transmit these viruses to humans and animals.

It is becoming increasingly clear that even native mosquito species can transmit a variety of viruses. The heatwave summer of 2018 saw the first outbreak of West Nile virus in eastern Germany. Since then, there have been annual cases of the disease in birds, horses and humans. "The transmission probability of this virus is directly temperature-dependent: If temperatures rise, so does the risk of infection," says Dr Renke Lühken, head of the Arbovirus Ecology research group at BNITM.

Complex interplay

The interplay between, for example, rising temperatures, rising sea levels, changed precipitation regimes and the risk of transmission of pathogens is very complex. This was recently described in a study by the University of Hawaii in Nature Climate Change.

Intelligent early warning system

Taking this into consideration, the BNITM is intensifying its contribution to mosquito research, surveillance and control. Particular mention should be made of the European Commission's award-winning project "EarlY WArning System for Mosquito borne diseases" (EYWA) and the BMBF junior research group "Fast real-time decision support for the control method of mosquito-borne viruses".

Both projects collect weather data, results of mosquito counts, information on virus detection e.g. in Europe and Germany and evaluate them with the help of mathematical models. This way, local outbreaks of mosquito-borne diseases can be predicted in the short term. This is important because mosquitoes can be controlled well in clearly defined areas and outbreaks can be brought under control quickly. This early warning system is now being established by BNITM in countries of the Global South such as Thailand and Côte d'Ivoire.

There are role models, says Schmidt-Chanasit. In Greece, for example, where the management of the EYWA consortium is based. There, EYWA provides such precise results of outbreak areas that risk zones can now be identified and mosquitoes can be combated in a targeted manner. Or the Kommunale Aktionsgemeinschaft zur Bekämpfung der Schnakenplage e.V. (KABS), an association of municipalities on the Upper Rhine. They joined forces decades ago and work, among other things, with mosquito-specific insecticides that are applied in breeding waters. KABS is also part of the international early warning system.

Further information and contact

Press release - Bernhard Nocht Institute for Tropical Medicine (BNITM)