Since 2012, the project “Eliminate Dengue: Brazil’s Challenge” is active in the country. The research is part of the Programme “Eliminate Dengue: Our Challenge”, which is testing a new method in Australia, Vietnam and Indonesia, coming to Brazil with Fiocruz, supported by Fiotec. The methodology consists in having the bacterium Wolbachia block the dengue virus transmission by the mosquito Aedes aegypti.

Wolbachia pipientis is an intracellular bacterium broadly present in insects, observed for the first time 70 years ago, in mosquitoes Culex pipiens. It was found in 1926, and since 1990, more than 1,500 scientific studies about Wolbachia were published in scientific journals. Scientists of the international program show that Wolbachia is capable of blocking the dengue virus transmission in the Aedes aegypti, sourcing a new, natural and self-sustainable proposal for controlling the disease.

Methodology

Wolbachia’s intracellular characteristic can be transmitted only vertically (from mother to child) by the egg of the female mosquito. In result, the success is directly related to the insect’s reproduction capacity.

The bacterium has an advantage due to the so-called “cytoplasmic incompatibility”: females with Wolbachia always generate descendants with Wolbachia in the reproduction process, whether coupling with males with or without the bacteria. And, when the females without Wolbachia couple with males with Wolbachia, the fertilized eggs die. 

Long term control

At first, there will be few Aedes aegypti with the bacteria in the mosquito population, and, thus, the reproductive advantage will be small. But, with the successive generations, the number of male and female mosquitoes with Wolbachia tends to increase until the whole mosquito population has this characteristic. Therefore, once the method is field established, in a certain place, the mosquitoes continue to transmit Wolbachia naturally to their descendents, not needing further intervention.

It is worth emphasizing that despite the broad range of hosts (70% of all insects in the world, including butterflies and several mosquitoes), this bacteria is not infectious and is not capable of infecting vertebrate beings, including humans.

The eggs of the mosquitoes with Wolbachia were brought from Australia to Brazil with the authorization of the Brazilian Institute of Environment and Natural Renewable Resources (Ibama), the relevant authority for this matter. With those eggs, a Brazilian group of Aedes aegypti with the bacteria was created in a Fiocruz’s laboratory. The project coordinator, Luciano Andrade de Moreira, from René Rachou Research Center (Fiocruz Minas), will soon release the mosquitoes of the group for living with the other mosquitoes.

*Source: IOC/Communication