Transgenic mosquitoes to fight malaria

Malaria is writing his own chapter in the history of medicine. Different strategies have achieved in recent years in reducing mortality and according to various estimates since 2000 have saved five million lives. However, there is still much to achieve so any move is welcome in the fight against a disease that kills every year around half a million people, 80% of them are African children under five. One of those initiatives that can have an impact in the coming years is now published by researchers at the University of California as they have succeeded in creating a resistant transgenic malaria mosquito.

Speaking of the treatment, mosquito nets and insecticides, every minute a child dies from malaria. This disease is caused by one of four types of parasites of the genus Plasmodium and is transmitted by the Anopheles mosquito. For this reason, there are two approaches to the eradication of the disease: remove the parasite from each zone or act against the mosquito.

The combined treatments based on artemisinin and future vaccine, still pending approval by WHO, but let us focus on removing the parasite from the blood or prevent infection.

Besides these medicines, there have been several strategies for combating the other major element in the history of the disease. The manipulation of mosquitoes is the idea that has long being attempted to act against the spread of malaria. Previous initiatives have tried using sterile males. As these mosquitoes mate only once in their life if the female does it with a sterile male would be unable to have children and thus reduce mosquito population. However, this strategy had limited success because to achieve a major impact must release a large number of these insects in a particular area, usually not as well received by the people living there. Also, if you load the mosquitoes that niche tend to be occupied by another animal, which may create more problems.

This research highlights the great role played in reducing malaria implementing insecticide-treated mosquito nets. According to a recent study published in Nature, between 2000 and 2015, the prevalence of Plasmodium falciparum infection in Africa (parasite typical of this region) was reduced by half and more than two thirds of that decline was due to the control of vectors.

However, both the vector and the parasite tend to adapt to the measures being developed to combat them. On the one hand, the parasite has developed resistance to the drugs and, secondly, the mosquito has learned to cope with mosquito nets. If this kind of insect is characterized by itching at dusk and in enclosed spaces, such as bedrooms, with the introduction of mosquito nets has been seen in the long term, they have been surviving the biting outside houses or hours earlier. Now there are more mosquitoes of this type. For that reason, any innovation will be well received.

The innovation that provided researchers at the University of California is the use of the technique of genetic cut and paste in malaria mosquitoes. This is to introduce genes into the insect to make it resistant to the malaria parasite. To do this, they used the CRISPR-Cas9 technique, developed by Jennifer Doudna and Emmanuelle Charpentier, who received the Princess of Asturias award this year for this method.

To test the effectiveness of this method, the researchers tested the Anopheles stephensi, a species of the genus Anopheles, a parasite that can transmit the malaria. This vector is in India and is an emerging vector, responsible for 12% of malaria transmission in this country (about 106,000 clinical cases in 2014) and recent outbreaks in Africa.

Having identified a number of genetic mutations that confer resistance to malaria, the researchers inserted genes with these embryos enzyme Cas9 into these mosquitoes, addressing a specific area of germline DNA to insert it modified genes. Furthermore, to assess the effectiveness of the technique, a gene that gave rise to descendants of these mosquitoes present eyes red fluorescent if inherited genes antimalarial was inserted. After these mosquitoes develop and mate, it was found that 99.5% of the offspring carry the genetic protection against malaria.

This opens the door to a real promise that this technique can be adapted to eliminate malaria. It is a significant step. Although created mosquitoes are not the last step. This technology allows us to efficiently create grades populations.

However, the results, although promising, does not mean they can loosen and genetically modified mosquitoes into the jungle to eradicate malaria. The researchers have to see the stability of the effector gene in different genetic backgrounds and under different environmental conditions and require research in the field.

Control and other strategies using drugs should be considered. In his case being studied ivermectin, a drug that makes when mosquitoes die when biting the person taking it. It is a complementary measure to vector control, but is being studied.