Mosquitoes are not only annoying, but sometimes extremely dangerous. Invasive species such as the Asian tiger mosquito can transmit severe tropical fevers. An RNA-based method could be used in the future to curb its spread in Europe. The idea: mosquito larvae absorb special particles filled with RNA from the water and die from them. Unlike conventional pesticides, this method would only hit mosquitoes and no other insects.
Summer time is mosquito time. But since species from tropical and Asian regions have become increasingly popular in this country, the little bloodsuckers are no longer just annoying, but also potentially dangerous. Invasive species such as the Asian tiger mosquito or the Japanese bush mosquito transmit, among other things, the Zika and West Nile viruses as well as dengue and yellow fever infections. But what to do about the uninvited guests? Conventional pesticides are associated with high collateral damage and also kill numerous other insects. Genetically modified mosquitoes, on the other hand, are rejected by the majority of the population. Mosquito control is therefore in a dilemma.
An ultimate mosquito weapon?
Researchers led by Ruth Müller from the Institute for Tropical Medicine in Antwerp, Belgium, have now evaluated a third, promising option for mosquito control. This is the technology of RNA interference, or RNAi for short. “The mosquito larvae are provided with food in the distribution area that contains double-stranded ribonucleic acids, or RNAs for short. These important information and functional carriers, which are found in every cell of living beings, then unfold their effect via the intestine of the larvae and switch off some of their genes, which are important for survival," explains Miklós Bálint from the Justus Liebig University in Giessen.
However, the RNAi technology is still in its infancy and is far from being ready for the European market. But the research team sees great potential in it. A key advantage of RNA interference is that, unlike conventional pesticides, it does not cause a deadly sweeping attack in the insect kingdom, but instead works in a targeted manner. "The RNA molecules can be produced in such a way that they are only effective against the respective mosquito species and do not endanger other insect species or humans," says Bálint. “Furthermore, no toxic residues are formed when they are broken down in the environment. And no genetically modified reproductive mosquitoes are produced with this method.”
High hurdles in development
In order to come as close as possible to this ideal of an anti-mosquito agent, Müller's team is currently researching double-stranded RNA pieces that are particularly suitable for mosquito control. But there is still a long way to go before these one day become functional "poison baits" for mosquitoes. For example, the "packaging" of the RNA balls still causes problems for the researchers. "A suitable formulation for this must not decompose too quickly in the environment, but should be absorbed in the form of particles by the mosquito larvae living in the water," reports Andreas Vilcinskas from the Fraunhofer Institute for Molecular Biology and Applied Ecology in Giessen, where he is currently working on a solution is filed. Nanoparticles, lipid droplets or chitin could be suitable as a suitable coating.
At the same time, environmental compatibility must not be neglected when developing RNAi, especially if the method is to be approved in the European Union. "There is little knowledge about the whereabouts of double-stranded RNAs in aquatic habitats," says the Müller team. Authorities could therefore request further toxicological studies and also evidence that RNA interference is actually safe for insect species that are currently not in the crosshairs. Another hurdle: "As with all other methods of controlling insect pests and disease vectors, there is concern that the use of RNAi could lead to the emergence of resistant insect populations." In the long term, the mosquito larvae could possibly become immune to the genetic poison bait.
Source: Senckenberg Research Institute and Natural History Museums; Specialist article: Biotechnology Advances, doi: 10.1016/j.biotechadv.2023.108167