Of mosquitoes and men
Esther Schnettler from the Bernhard Nocht Institute for Tropical Medicine observes the spread of mosquitoes and their viruses.
For most people, mosquitoes are bothersome pests which not only bite and make annoying sounds but which also transmit diseases. However, for Esther Schnettler, they are a highly interesting subject for research about which according to her, we should try to discover as much as possible, particularly in the current age of climate change. Since 2016, Schnettler, at just 40 years old, has been on a DZIF Professorship at the Bernhard Nocht Institute for Tropical Medicine (BNITM) where she ensures that the spread of mosquitoes does not go unnoticed.
“Of course I dislike mosquito bites,” Esther Schnettler admits with a smile, right at the beginning of our conversation. “However, at my workplace here at the BNITM, high above the Elbe River, I do not need to worry about this as the mosquitoes in the containers are carefully counted. I would immediately notice should one go missing.” She has dedicated herself to the study of mosquitoes, or to put it more precisely: she has dedicated herself to the study of mosquitoes and the arboviruses they host which are subsequently transmitted to humans via mosquito bites. This young professor’s real interest is to find out how it is possible for arboviruses, which cause West Nile fever, dengue fever or chikungunya fever for example, to survive in both mosquitoes and humans, two very different host systems? And what should we do when with climate change, mosquitoes from warmer regions start to spread north thus increasing the spread tropical diseases here?
Questions such as these were not even being considered by Esther Schnettler when she first started her studies in 2001. “I enjoyed biology and mathematics in particular and consequently felt that biotechnology studies would suit me well.” She therefore logically decided to study in the Netherlands where biotechnology had been restructured to offer novel bachelor and master degree programmes including plenty of teaching in English. Learning to speak Dutch or “Nederlands spreken” was, however, a prerequisite for the first year. She enjoyed learning the language knowing that “Once you learn it, you never forget it.” She spent the entire period of her studies in the Netherlands with the exception of a 6-month internship that she completed as “experience abroad” in Germany.
About plants, animals and viruses
Esther Schnettler quickly discovered that she found the molecular biology of viruses and other small organisms contained in the biotechnology vessels more interesting than the actual process technology itself. In September 2010, Schnettler was awarded a doctorate for her work on plant viruses, which laid the foundation for her career. For her postdoctoral research, she specifically looked for a laboratory conducting research on viruses with the main language used being English: “Which was my partner’s prerequisite for accompanying me,” she says. Consequently, she ended up in Scotland, initially in Edinburgh and then in Glasgow, where she conducted research on arboviruses at the “Centre for Virus Research” up until 2016. “This was a special time for me as I had the opportunity to work on many different projects and was also extremely lucky with my supervisor,” she remembers.
Esther Schnettler often uses the word “luck” when she recalls her career path, but her advancement and continuous drive towards reaching new goals are probably more likely due to her decisive and dynamic personality. She left work for short periods three times and for good reason, as she took maternity leave for her three children who are now 6 years, 3 years and 8 months of age. How does one manage to work almost full time with three small children? “I have been extremely lucky here because I have a stay-at-home husband at my side.”
About arboviruses and mosquitoes
Esther Schnettler left Glasgow in 2016 when she was “actually just planning on buying a house.” At the time, the DZIF and the Bernhard Nocht Institute were looking for a medical entomologist and lured Esther Schnettler into taking up a professorship. She does not view herself as a classic entomologist and insect researcher – she is not familiar with typical insect display cases containing pinned butterflies and bugs. However, medical entomology and the research theme of the position suited her perfectly. It involved immune responses of arthropods to arboviral infections and their impact on vector competence. What may initially sound incomprehensible for lay people, fulfilled a dream for Esther Schnettler. She could finally study in detail how mosquitoes deal with viruses, how they survive infection and transmit diseases. “In my work, vector competence is actually a key word,” Schnettler explains. It is about recognising why certain mosquitoes are able to better transmit certain viruses than others and, of course, about what threat this poses to humans.
Female mosquitoes have to be stuck on a dish, in order to obtain and test their saliva. The saliva is obtained with the tip of a pipette filled with fluid.
The BNITM and the DZIF offer excellent facilities for this job, providing a high biosafety insectary in which mosquitoes can be tested for their ability to transmit pathogenic viruses at different temperatures. The experiments are somewhat complicated and must be handled delicately. Initially, approximately 100 mosquitoes are bred in cages and small hoovers are used to suck them into containers. They are subsequently anaesthetised for brief periods of time in order to select the females, as only female mosquitoes suck blood and transmit diseases at a later stage. “We starve them for 24 hours and then provide them with a meal of blood containing viruses, depending on the experiment in question,” Schnettler explains. The large blood-bloated mosquitoes are then sorted and incubated at different temperatures and over different lengths of time. These mosquitoes are then “fastened” onto plates and their saliva is extracted using a pipette tip. The saliva is then investigated for specific virus transmissions. “Naturally, the mosquito bite is only simulated,” Schnettler explains, “but this is sufficient enough to learn more about viral transmission via mosquitoes.”
About mosquitos and climate change
At the DZIF, Esther Schnettler also heads a research group that works on the import and spread of new pathogens by mosquitoes, together with Jonas Schmidt-Chanasit’s research group and other entomologic research groups in Germany. The researchers conduct nationwide recordings of native mosquito types with particular focus on identifying new invasive types, such as the Asian tiger mosquito as early as possible. These types of mosquito have already been found in Germany and laboratory experiments have shown that they are able to transmit chikungungya viruses at moderate, non-tropical temperatures of 18oC. However, they occur only very rarely and do not pose a significant threat. “Yet we must observe mosquitoes closely and keep reassessing the risk of tropical diseases, particularly in view of the increasing temperatures due to climate change,” emphasizes Esther Schnettler. It is greatly reassuring to know that this “Master of Mosquito Research” is observing and assessing the risks at the DZIF constantly.
