Aedes Aegypti Mosquito Fighting the Most Dangerous Animal in the World

The Aedes aegypti mosquito, which carries Zika, dengue fever and other illnesses, appears unstoppable. It is posing a unique threat to this year's Olympic Games in Rio and is rapidly spreading around the world. Europe, too, is at risk.


By , Hauke Goos and

It is a Monday morning in April and a young man named Leandro Fornitan is heading into battle together with 300,000 male mosquitoes of the Aedes aegypti species. The insects are stored in several hundred plastic containers that have been loaded onto the bed of a truck Fornitan is driving through the streets of a residential district in the Brazilian city of Piracicaba. Aside from a few dogs, the streets are empty at this early hour.

The mosquitoes in the containers are 11 days old. And the deadly secret they are carrying with them is invisible.

Just like Aedes aegypti mosquitoes that grow up in the wild, Fornitan's specimens have the same black-and-white striped pattern reminiscent of Adidas jogging suits. They all have the same bushy feelers, with which they navigate through their short lives -- a life which, for a male Aedes, has but one aim: reproduction.

But the mosquitoes that Fornitan will release into the wild this morning were bred in a laboratory. And they possess an artificial genetic modification that will be passed on during mating. That gene produces a protein called tTAV, which will ensure that the mosquitoes' larvae will die before reaching adulthood.

In other words, the genetically modified mosquitoes that Fornitan is currently testing in Piracicaba are manmade assassins being sent into battle against their own species. It is a kind of biological weapon, deployed with the goal of decimating the population of Aedes aegypti, a species that carries around a dozen diseases, many of them deadly, including yellow fever, dengue fever and other, largely unresearched illnesses such as chikungunya and Zika.

"This mosquito," says Fornitan, "is the most dangerous animal in the world." Indeed, Aedes aegypti presents a threat to some 4 billion people across the globe.

The world long approached the Aedes agypti plague as though it were a storm that would soon blow over, but it has now become a fixture in large cities in the tropics. If nothing is done, experts say, more and more people will die as a result. And it has also become clear that some of the tropical diseases carried by this insect are coming to Europe. Partly, that is the result of rising temperatures on the European continent. In the southwestern German city of Freiburg, for example, scientists have determined that a population of Aedes mosquitoes survived the German winter for the first time. It used to be that only those who traveled to the tropics were at risk of becoming infected with tropical illnesses. But now, many in Europe must face the prospect of the tropics coming to them.

It was images from Brazil that sent a jolt of fear around the world at the beginning of this year. Across the country, babies were suddenly being born with heads that were misshapen and too small. When indications mounted that this curious increase in cases of so-called microcephaly was connected to the Zika epidemic that had stormed across Brazil in the previous months, the World Health Organization (WHO) declared an international emergency.

The Mosquito of the 21st Century

Brazil mobilized 220,000 soldiers for the battle, sending them through bathrooms, yards and garages to eliminate standing water where female Aedes mosquitoes lay their eggs. But the campaign did little to reduce the threat. In the first four months of this year, officials registered 100,000 additional cases thought to be Zika. In addition, almost a million people were infected with dengue fever, more than ever before in such a short span of time.

There is no vaccine against the Zika virus and there is no medicine that can prevent people from becoming infected. In March, medical researchers said that Zika can also be transmitted via sexual intercourse and, as if that weren't enough, 151 health experts wrote an open letter in May demanding that the Olympic Games -- set to kick off in Rio in two weeks -- be postponed or moved. Taking the risk of holding the games as planned, they said, would be irresponsible. The city is expecting a half-million visitors. If only a tiny fraction of them become infected by the virus, these games -- intended to crown Brazil's climb to economic power status -- could mark the beginnings of a catastrophe.

The fear of a global Zika outbreak has put the spotlight on an insect that was long seen as the smaller, less dangerous brother of the Anopheles, which spreads malaria. But times are changing. Whereas the Anopheles was the mosquito of the 20th century, the Aedes aegypti seems intent on taking that crown for the 21st.

The number of people dying of malaria has long been in decline, but Aedes-spread dengue fever, by contrast, is now considered the fastest spreading mosquito-borne illness in the world. Fully 128 countries are now considered at risk of dengue and around 400 million people become infected each year, according to WHO. Most of them suffer from rashes, joint pain and high fever. But an estimated 20,000 per year have a different reaction: They experience severe internal bleeding which often ends in death.

It took dengue fever half a century before the WHO's map of affected areas slowly turned red. But in the case of Zika, it is as though someone dumped a bucket of red paint on half the world. After the virus arrived in Brazil in 2013, likely by plane from French Polynesia, it only took a few months for it to spread to 60 countries. And everywhere Zika became established, it had been preceded by the Aedes aegypti mosquito.

 Coming to Europe: Areas of the world at risk of diseases transmitted by the Aedes aegypti mosquito.

Coming to Europe: Areas of the world at risk of diseases transmitted by the Aedes aegypti mosquito.

The mosquito was also there when chikungunya fever broke out on the island of La Réunion in 2005. It was there when chikungunya spread to India and it was there when the virus jumped from the Caribbean to the American mainland. Even yellow fever, which long seemed to have been eradicated, is making a comeback. By the time Angola, the Democratic Republic of Congo and Uganda this spring reported the worst outbreak of the disease in decades, the mosquito had already infected 2,000 people. Three hundred of them died.

On the Front Lines

What, though, can be done? Will it be possible to eradicate the Aedes aegypti mosquito once and for all, or will we have to be satisfied with protecting ourselves to some degree from the diseases the insect carries?

The genetically modified laboratory mosquito from the British company Oxitec is the most innovative strategy yet developed to combat the insects. In trials on the Cayman Islands and in Panama, Fornitan says, their method succeeded in reducing the wild Aedes population by 90 percent in just a few months. They are now trying to do the same in Piracicaba.

Leandro Fornitan heads to the front lines six days a week. Next to him is an open laptop showing a map of the residential district. Whenever the computer peeps an alert, Fornitan reaches behind him, takes the lid off of one of the mosquito containers, holds it to a funnel sticking through his cracked window and pounds on the bottom of the container. A fan and the mosquitoes' instincts do the rest.

"Normally," Fornitan says, "we need one container every 100 meters. But there are hotspots where we release more" -- such as scrap yards, bus stops and supermarkets.

The Aedes mosquito is never far from places where people live, work, play or wait. It is a problem facing Piracicaba and Rio de Janeiro, but also dozens of other cities worldwide, like Jakarta, Luanda and Singapore. They hide behind curtains, underneath beds and inside cars, constantly on the search for the scent of humans. Aedes aegypti is attracted both by the carbon dioxide that we exhale and by our perspiration, an alluring combination of butanoic acid and propanoic acid. Female mosquitoes pursue this scent until they come close enough to their victims to sense the warmth and dampness that everyone's body emits.

In contrast to the Anopheles, which primarily bites at dusk and at night, Aedes aegypti females do most of their hunting during the daytime. You hardly notice when she caresses your skin with her feelers in the search for blood veins. The mosquito's proboscis is made up of a lower lip and its six bristles. Some of the bristles have tiny hooks at their tips, which are drilled into the skin when the mosquito moves her head back and forth -- until it finds a capillary to suck blood from.

Blood is vital for female mosquitoes. It provides the protein necessary to complete the egg creation process.

To prevent blood from quickly clotting, mosquitoes secrete an anticoagulant into their host's bodies. It is this exchange of bodily fluids that makes mosquitoes into a so-called vector -- an animal that transmits pathogens.


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Keri 07/22/2016
What's up Spiegel, you didn't blame Putin. You're slipping
tim_pfister 07/23/2016
DDT will work. Not using it for 40+ years has killed millions.
juan_gonzalez 07/23/2016
3. The US wants to use Naled pesticide on Puerto Rico
Because of the outbreak of ZIKA in Puerto Rico the US CDC (Centers for Disease Control and Prevention) wants to use a harmful pesticide call Naled on us which is highly toxic to animals, plants and humans. Our Government is pro to spraying such pesticide because the US government in exchange promised money for the island Health care system.
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