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Scientists investigate how to combat the spread of viruses from mosquitoes

A research group is testing a new method to combat the spread of viruses by mosquitoes. Mosquitoes can be responsible for the spread of serious diseases such as yellow fever, dengue fever and the Zika virus.

Research by Beth McGraw, professor of entomology at the State University of Pennsylvania, gives new hope of using a particular bacterium, called Wolbachia, which is present in about half of all insects, to block the replication of the virus within mosquitoes.

The article published in Virus Evolution describes in particular how this bacterium can be used to stop the spread of dengue fever and how the virus seems not to develop resistance to it, at least in laboratory experiments. Many mosquitoes carrying this virus, however, do not have this bacterium and some laboratory work is needed to place it inside the cells of these mosquitoes.

However, once this step was taken, the researchers realized that the dengue viruses grown with the Wolbachia bacterium were much less effective in infecting mosquito cells and had a reduced ability to replicate than viruses grown without the bacterium.

Since the mosquito populations are very large and these are only laboratory experiments on a few small numbers, it is possible that once this method is applied in nature the virus can quickly develop resistance to the bacterium.

In any case, the fact that there is a bacterium that almost completely blocks the dengue fever virus is very attractive information, also because this bacterium seems to spread very quickly and very efficiently among mosquitoes.

This is because it causes a curious effect on males: those containing this bacterium can no longer reproduce with females without the bacterium. This means that males with the bacterium inside their cells prevent females without the bacterium from reproducing and that each generation of mosquitoes has more and more specimens containing the bacterium.

Currently, several releases of Wolbachia are already underway in tropical and subtropical areas where the mosquito of the species Aedes aegypti, considered as the main vector of the dengue virus, is more present. These releases will help to understand whether the virus can actually develop resistance in nature.

A resistance that however has not been developed by the virus in the laboratory, something that gives hope, as McGraw herself reports: “I am constantly surprised by Wolbachia. I thought we would have dengue variants that would develop resistance: Wolbachia is doing a better job than I expected in controlling viral replication in cells.”