As Naked Science has repeatedly pointed out, the mosquito is the most dangerous animal on the planet for humans. According to some estimates, in just the history of our species, they have killed 50 billion people out of 110 billion who have ever lived. The main (but not the only) cause of danger is mosquito-borne malaria. Contrary to misconceptions, it is quite tolerated by ordinary mosquitoes living in Russia, which is why, before DDT, malaria was endemic here and caused up to tens of millions of cases per year. The campaign against DDT since the 1970s has halted the decline of malaria so that it still kills people (mostly children) far more often than famines and wars combined. We recently wrote about attempts to solve this issue through non-chemical pesticides, but there is another approach – biological.
Within its framework, the Anglo-American company Oxitec operates, which created genetically modified male mosquitoes, from which wingless offspring were born. Naturally, it could no longer pose a threat to humans. However, attempts to release such GM mosquitoes in Brazil earlier led to an unexpected result: wild female mosquitoes somehow learned to understand that they were GM mosquitoes and avoided mating. In addition, a small part of these insects, due to modification errors, still left viable offspring.
Now US researchers decided to take a fundamentally different path – to create not “defective” mosquitoes, but those that are superior to natural ones. To do this, they used Cas9 (guided by RNA guides). endonuclease), introducing with its help into the DNA of mosquitoes two genes responsible for the production of two antibodies. Each of them fights the malarial Plasmodium, a protozoan that infects humans and mosquitoes and causes malaria.
As a result, scientists managed to achieve mating of such male “supermosquitoes” with females in the laboratory. Moreover, if for Anopheles gambiae, females were still more likely to mate with unmodified males, then for another species of mosquitoes – malaria carriers, Anopheles coluzzii, GM males attracted females, like wild ones, which is why their “antimalarial genes” quickly spread in the population.
The long absence of DDT treatment is ultimately leading African countries to skyrocket the incidence of malaria. Often it is exponential / © Wikimedia Commons
At the same time, both the frequency of infection of modified mosquitoes with malarial plasmodia and the number of plasmodia per individual, if infection did occur, were significantly reduced. According to the calculations of the authors of the work, similar changes in nature would reduce the likelihood of infection of people living next to such mosquitoes by 90% or more.
The new approach has great advantages over the old ones. Firstly, it allows the modified genes of “supermosquitoes” to spread throughout the mosquito population without the “penalty”, as in the previous “inferior” GM mosquitoes. Secondly, such genes are unlikely to be accidentally ousted from the population by selection: after all, mosquitoes that are less ill will be able to reproduce faster in the wild.
The disadvantages of the approach are also quite obvious. Despite these antibodies, Plasmodium could still occasionally infect mosquitoes. This means that under natural conditions it will receive serious selection pressure towards the ability to develop, despite contact with new antibodies. In the future, this may lead to the appearance of a plasmodium completely insensitive to them.
In addition, mosquitoes carry not only malaria, but also dengue, as well as West Nile fever. If pesticides solve all these problems at once (and without destabilizing ecosystems, as is known from New Caledonia and other mosquito-free ecosystems), then the “genetically improve mosquitoes without exterminating them” approach requires separate modifications against the causative agents of each of these infections, and this is clearly more difficult. .
Now the developers of the new “supermosquitoes” are negotiating with the authorities of the African island state of Sao Tome and Principe to release modified insects there. If the negotiations are successful, we will soon be able to assess the prospects of the new method in practice.
2023-07-11 14:02:52
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