Over time, the manipulated genome disappears by itself
Another catch is that the classic SIT cannot be applied to every type of insect as well as it is with the prime example of the Mediterranean fruit fly. “You need a suitable system in order to be able to breed only males en masse,” explains Schetelig. This is where genetic engineering comes into play, with which the female sex uses genetic tricks like that tTAV-System can be switched off.
Oxitec’s OX5034 mosquitoes differ from the classic SIT animals in one essential point: The OX5034 males used are just not sterile. They are supposed to be killing the female tTAV-Generally passed on to the next generation. This is desirable in order to reduce the population over the course of several mating cycles without having to continuously release more males – which is absolutely necessary in classic SIT. After a few generations, the OX5034 males disappear from nature, as Mendelian rules apply, i.e. only half of the male offspring inherit the OX5034 genome.
Oxitec’s release plans counter the distrust of various environmental groups in Florida. Only in autumn 2019 had a publication in the specialist journal »Scientific Reports« caused negative headlines worldwide: Oxitec’s transgenic mosquitoes would spread in Brazil, was read in a number of media. “The work was misleading,” says Wimmer and is not alone with his criticism – including the undifferentiated representation in serious media. The study found no negative or unexpected effects on humans or the environment, but it was speculated. The editorial team of “Scientific Reports” has reacted in the meantime: in mid-May 2020 they published a statement. Six of the ten authors of the controversial study agreed with theirs »Letter of Concern« the corrections listed.
In Brazil, Oxitec’s attempts are met with a high degree of approval. The decisive factor is the level of suffering caused by the Zika and dengue infections, says Wimmer.
A question of the development of resistance
Wimmer and Schetelig are not at ease. Both are researching the genetic further development of SIT-like systems in various pests, including the cherry vinegar fly, which also causes great damage here on land. “A method that specifically only attacks this species would be a blessing,” says Wimmer. One does not have to endorse every idea about the genetic modification of organisms. “But to categorically reject them is also not the right way.”
“The question is: what alternatives do we have? Do we want to accept more deaths from malaria and dengue fever? Do we want to spray tons of higher concentrations of unspecific insecticides and thereby cause the death of other species and pollution of the soil and the environment? Or do we want to try a specific method? ”Asks Schetelig.
Both scientists criticize Oxitec’s experiments on one point in common: instead of relying on just one killing mechanism, two should be used. “The tTAV-System has been very well researched and is used by numerous working groups. If insects develop resistance, on the other hand, a potentially very effective technology would be prematurely burned for other approaches, ”explains Wimmer.
Two recently published papers suggest that this is possible: Experiments with the fruit fly Drosophila melanogaster indicate that resistance to the tTAV-System to be available or through Mutation arise spontaneously can. According to Oxitec’s press spokesman, Joshua Van Raalte, no resistance to an Oxitec product line has yet been documented.
Genetic engineering makes some residents uncomfortable
Many ordinary people are plagued by other worries: the mere thought of GM mosquitoes buzzing through the air makes them uncomfortable – this is also shown by the comments that the US environmental agency received on Oxitec’s application for approval: 31,174 comments were against, 56 comments for them Try out. The proponents saw benefits for health and the environment, especially in the saving of non-specific pesticides. Many opposing voices worry about unforeseen ecological consequences. What happens when other animals eat genetically modified mosquitoes? And what if one species is completely exterminated? Then what happens to those animals that feed on them? Schetelig believes these concerns are unfounded. “This method can only contain the yellow fever mosquitoes, not exterminate them,” says the expert.
The US Environmental Protection Agency has in one publicly viewable, 150-page paper in detail position added to the comments received. In her risk analysis, which can also be viewed, she comes to the conclusion that Oxitec’s experiments have “no unreasonable negative effects on people or the environment”.
In one Artikel in »The Conversation« However, several scientists criticize the lack of transparency in the decision of the environmental authority and argue, among other things, for a broader risk assessment by independent third-party researchers. Precisely because the method is such a promising tool in the fight against diseases, open, comprehensive and participatory decision-making is required.
In order to start the release experiments in Florida, Oxitec still needs the approval of the local authorities. Normally it would have been voted on July 21st. Because of the corona pandemic, the vote was postponed to August. It is by no means certain whether the application will go through. In 2016, Oxitec failed to overcome this last hurdle.
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