Aedes aegypti, the mosquito responsible for several tropical diseases
Aedes aegypti, the mosquito responsible for several tropical diseases

Aedes aegypti, the mosquito responsible for several tropical diseases

Every summer seems to be the same. The Ministry of Health launches television ads asking people to prevent the proliferation of the Aedes aegypti, the mosquito that causes dengue fever. They like clean, standing water, which can easily accumulate in gardens, potted plants, and so forth. Yet every summer inevitably sees a rise in the number of dengue fever cases in the country’s warmest areas, such as Rio de Janeiro and the Northeast. Between 2015 and 2016, though, things took a turn for the worse.

The Aedes aegypti brought not only dengue fever, but also the zika virus, chikungunya, and yellow fever. The explosive zika outbreak created panic once Brazilian researchers discovered a link between the virus and cases of microcephaly in babies whose mothers were infected during pregnancy.

For years, Brazil has been losing the war against the Aedes aegypti, but research from the Institute of Biomedical Sciences of the University of São Paulo is developing a kind of male insect that could keep the mosquitoes from breeding.

This is how the technique works: by manipulating the animal’s genetic code, researchers were able to induce the males to produce defective spermatozoids. So, when they copulate, the resulting eggs do not create new mosquitoes, thus reducing the local population, explains Margareth Capurro, the leading researcher behind the development of the genetically modified insect.

aedes aegypti larvae

Aedes aegypti larvae

Inspired by agriculture

Genetically-modified breeds of pests have been introduced on farms in order to reduce the populations of damaging agents and the losses of crops. Biofactories produce the insects that will be used in the fields, a technique that has been applied especially on fruit plantations, according to Ms. Capurro.

Before the genetically-modified mosquitoes reach the phase of mass production, there are still some steps ahead.

The first was the successful tests in the laboratory. Phase two will have the mosquitoes living in an outside environment – albeit still contained in cages. What the scientists want to find out is if these genetically-modified specimens can survive in natural conditions and if they will be able to copulate in windy and rainy environments. This is an important step because it will be possible to identify genetic traits that researchers may want to eliminate in their final product.

Technology will be available for free

The genome and the techniques used to create these animals will be made available free of royalties to any countries where zika, chikungunya, dengue, or yellow fever are endemic. A part of the research is being financed by the International Atomic Energy Agency, an organization linked to the United Nations, and organization members will have access to the new technologies.

Ms. Capurro says that her mosquitoes alone cannot combat tropical diseases and must be part of a coordinated strategy that includes analyzing local contexts and needs.

Brazil already eliminated the mosquito once before

Between the 1930s and 1950s, a program financed by the Rockefeller Foundation all but eradicated the Aedes aegypti in Brazil. The goal at the time was to get rid of yellow fever, also transmitted by the dengue fever and Zika mosquito. Rigidly-trained health inspectors applied DDT on the streets and were easily able to break into any private property suspected of mosquito breeding sites.

Back then, Brazil was under a dictatorship and state agents had enormous powers.

Some researchers believe that Latin America eradicated the mosquito after similar efforts in other countries. But it was in the Southern U.S. states that the Aedes aegypti remained alive, according to Brazilian researcher Rodrigo Cesar Magalhães. As American laws prevented health officials from having access to many private lands, the mosquito was able to continue breeding.

His Ph.D. thesis from the Oswaldo Cruz Foundation, in association with the University of Maryland, analyzes the efforts to eradicate the mosquito in the Americas between 1918 and 1968.

Yellow fever surge in 2018

While Brazil has been successful in decreasing the number of people infected by dengue, chikungunya and the zika virus, yellow fever has been an increasingly greater concern. At the beginning of 2018 the country saw the numbers rise sharply: it has been the worst yellow fever surge since 1980. From July 2017 to March 2018, 846 cases were confirmed, with 260 deaths.

In the previous year, the country had 597 cases and 190 deaths.

SocietyJul 04, 2018

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BY Diogo Rodriguez

Rodriguez is a social scientist and journalist based in São Paulo.