The mosquito is the most dangerous animal in the world, leading to diseases that kill one million people a year. Now the Zika virus, which is carried by mosquitoes, has been linked to the thousands of babies born with brain defects in South America. If insects are deleted?
There are 3,500 known species of mosquitoes, but most people do not bother humans at all living plant and fruit nectar.
It is only the females of only 6% of the species that draw blood from humans – to help them develop their eggs. Of these only half carry parasites that cause human diseases. But the impact of these 100 species is devastating.
“Half the world’s population is at risk of a disease transmitted by mosquitoes,” says Frances Hawkes, the Natural Resources Institute, University of Greenwich. “They have had an incalculable impact on human misery.”
Aedes aegypti – diseases such as Zika, yellow fever and dengue spreads; It originated in Africa, but is found in tropical and subtropical regions around the world
Aedes albopictus – diseases such as yellow fever and dengue fever and West Nile virus spreads; It originated in Southeast Asia, but is now found in tropical and subtropical regions around the world
Anopheles gambiae (pictured above) – also known as the African malaria mosquito, the species is one of the most efficient for the spread of the disease transmitters.
More than a million people, most of the poorest nations, die each year because of mosquito as malaria, dengue and yellow fever transmitted diseases.
Some mosquitoes also carry the Zika virus, which was first thought to cause only mild fever and rashes. However, scientists are now concerned that can harm babies in the womb. The Zika virus has been linked to an increase in microcephaly – where babies are born with smaller heads – in Brazil.
There is a constant effort to educate people to use treated mosquito nets and other tactics to avoid being bitten. But it would just be easier to make an entire species of mosquitoes carrying diseases extinct?
Biologist Olivia Judson has supported “specicide” 30 types of mosquitoes. She said that doing this would save one million lives and only decreases the genetic diversity of the family of mosquitoes by 1%. “We consider the strike with maximum force,” he told The New York Times.
In Britain, scientists at the University of Oxford and biotechnology company Oxitec been genetically modified (GM) male Aedes aegypti – a species of mosquito that transmits both the Zika virus and dengue. These transgenic males carry a gene that stops their offspring developing properly. This second generation of mosquitoes then die before they can reproduce and become carriers of the disease themselves.
About three million of these modified mosquitoes were released in a site in the Cayman Islands, between 2009 and 2010. Oxitec reported a reduction of 96% in comparison with mosquitoes nearby areas. A trial is currently taking place at a site in Brazil has reduced the number by 92%.
So are there any disadvantages to eliminating mosquitoes? According to Phil Lounibos, an entomologist at the University of Florida, mosquito eradication “is fraught with undesirable side effects.”
He says the mosquitoes that feed primarily on nectar from plants, are important pollinators. They are also a source of food for birds and bats while their young – as larvae – are consumed by fish and frogs. This could have an effect above and down the food chain.
However, some say that the role of the mosquito species as food and pollinators would be quickly filled by other insects. “We were not a wasteland every time a species disappears,” Judson said.
But Lounibos, the fact this niche would be filled by another insect is part of the problem. He warns that mosquitoes could be replaced by an insect “equally or more undesirable from the point of view of public health.” His replacement could conceivably spread disease even further and faster than mosquitoes today.
Science writer David Quammen argued that mosquitoes have limited the destructive impact of humanity on nature. “Mosquitoes do rainforests, for humans, virtually uninhabitable,” he said.
Rainforests, home to a large part of our total plant and animal species are under serious threat of destruction by man. “Nothing has done more to delay this catastrophe in the last 10,000 years, the mosquito,” Quammen said.
But the destruction of a species is not only a scientific issue, it’s also a philosophical one. There would be some who say it is totally unacceptable to deliberately wipe a species that is a danger to humans when humans are a threat to many species.
“An argument against is that it would be morally wrong to eliminate an entire species,” says Jonathan Pugh, from Uehiro Centre of the University of Oxford for Practical Ethics.
And yet, that’s not an argument that we apply to all species, says Pugh. “When I eradicated the smallpox virus, which caused smallpox, which rightly celebrated.
“We have to ask, do you have any valuable skills? For example, is sensitive and therefore have the capacity to suffer pain? Scientists say mosquitoes have no emotional response to pain as we do.
“We also have a good reason to get rid of them? With the mosquitoes, which are the main carriers of many diseases.”
Map areas described in high, moderate and low risk of malaria
The question is likely to remain hypothetical, whatever the level of concern by Zika, malaria and dengue. Despite the success of reducing the number of mosquitoes in smaller areas, many scientists say speices eliminate a whole would be impossible.
“There is no silver bullet,” says Hawkes. “Field trials using genetically modified mosquitoes have been moderately successful, but involved releasing millions of insects modified to cover only a small area.
“It would get every female mosquito to breed with sterile males in a large area very difficult. Instead, we should be seeking to combine this with other techniques.”
Innovative ways to combat mosquitoes are being developed worldwide. Scientists at Kew Gardens in London are developing a sensor that can detect each different species of mosquitoes of its peculiar rhythm wing. They plan to equip villagers in rural Indonesia with mobile acoustic sensors to track disease-carrying mosquitoes. This would help manage future outbreaks.
Meanwhile, scientists at the London School of Tropical Medicine have discovered how female mosquitoes are attracted to certain body odors, raising hopes of more effective repellents.
Another promising avenue is the genetically engineered mosquitoes to make them resistant to parasites that cause disease. In Australia, the Eliminate Dengue program is using naturally occurring bacteria to reduce the ability of dengue mosquitoes to pass between people.
“This is a more realistic approach to the alleviation of disease transmitted by mosquitoes approach,” says Lounibos.
Meanwhile, scientists at the US They have raised a GM mosquito with a new gene in the laboratory that makes it resistant to the malaria parasite.
“We’re playing an evolutionary game with mosquitoes,” says Hawkes. “Hopefully it’s one that can reach the top of the next 10-15 years.”
This article was first published in the BBC