Brazil: Rio to Fight Zika with Massive Release of Bacteria-Infected Mosquitoes

ScientificAmerican - Two major philanthropic organizations, along with the United States and Britain, announced on Wednesday an ambitious experiment to combat mosquito-borne diseases in cities by infecting the insects with crafty bacteria.

Researchers have used the bacteria, known as Wolbachia, in trials in places including Australia and Brazil in recent years. But those efforts were small, reaching areas with tens of thousands of residents.

The new trials will cover urban areas with millions of people. The goal: to see if the promising results from the early field trials can be replicated, and, possibly, to demonstrate that the approach can halt viruses like Zika and yellow fever.

“This is an order of magnitude bigger than anything that’s been attempted before,” said Mike Turner, acting director of science at the Wellcome Trust, one of the groups funding the effort. “That’s the question—can you do it to scale?”

The US and UK governments and the Gates Foundation are also contributing to the $18 million campaign. The group running the trials, the Eliminate Dengue Program, will be testing how loading Aedes aegypti mosquitoes with the Wolbachia bacteria affects cases of Zika, dengue, and chikungunya in cities in Brazil and Colombia over two to three years.

Wolbachia bacteria are found naturally in many insects, but not Aedes aegypti. When the bacteria are introduced to these mosquitoes, they take up residence in the insects’ cells, preventing viruses from multiplying and from being passed to people the insects bite. When mosquitoes with Wolbachia are released into the wild and breed, their offspring are born with the bacteria and can’t spread disease either.

Eliminate Dengue has run trials in Colombia, Brazil, Vietnam, Indonesia, and Australia over the past five years. The new trials will ramp up those efforts in Colombia and Brazil, the two countries hardest hit by the recent Zika outbreak.

In Colombia, the trial will take place in the city of Bello, and in Brazil, it will cover parts of the greater Rio de Janeiro area. Because lots of people and lots of mosquitoes live so densely in cities, urban areas are more vulnerable to mosquito-borne diseases than rural areas. Aedes aegypti only fly a few hundred yards in their lifetimes.