If you have ever tried to fall asleep with one in your room, you know they are irritating. But in many places, mosquitoes do much more than cause itching. Due to their ability to suck blood, some species of mosquitoes transmit diseases from one host to another, such as Zika virus, dengue fever, yellow fever and chikungunya. Many of these diseases are traditionally considered tropical diseases, but they are becoming increasingly distant from Ecuador due to climate change. The person responsible for the ailments listed above is the yellow fever mosquito, Aedes aegypti, an invasive mosquito imported from Africa on slave ships more than 400 years ago.
A new study published today in the Journal of Insect Science ask a question about the yellow fever mosquito that has never been asked before: how much can you insert into a syringe? The answer: more than you probably think. Researchers at the State University of New Mexico and other institutions have found that male mosquitoes infected by a syringe (240 mosquitoes per cubic centimeter, or about 1,200 per teaspoon) can survive for 24 hours and resume their flight. This is the first exploration of a new line of research that could help reduce mosquitoes in areas of the country colonized by Aedes aegypti. The research has also produced this incredible gif:
"They can survive this type of stress much better than a vertebrate animal," says study author Immo Hansen of New Mexico State University. Insects have exoskeletons and can persist longer in low-altitude environments, he says.
Why would scientists want to pack mosquitoes in a syringe? To ship them by mail, of course. One method of population reduction is the technique of sterile insects, in which infertile mosquitoes of yellow fever are introduced into a wild population. In theory, they always do all that fertile males do, like mates, with the essential difference that no child of their offspring comes from their unions. Only females suck the blood and spread the disease. The infiltration of these impotent males therefore only creates more competition for members of the species that would otherwise proliferate. But mosquitoes must be specially bred in a laboratory. Scientists need to know how to ship the insects from the laboratory where they were created to the wild populations with which they are supposed to reproduce.
This technique was developed in the 1950s to control worm flies in the Americas, at least there. Screw worms are all raised in a central facility and shipped as nymphs in crates. Mosquitoes must be shipped as adults and they do not fly very long during their life (just over 200 meters). This means that they must be released very close to wild populations.
Companies like Alphabet (Google) are betting that the use of drones to introduce sterile mosquitoes into wild populations will help fight the spreading insects of the disease, but there is no solid, publicly available scientific evidence to show that this is the case. The truth is that Alphabet's life sciences arm runs a program called Debug that includes a project to breed and spread male mosquitoes infected with a common bacterium that prevents them from having viable offspring. He has conducted two tests, one in California and the other in Australia.
"I'm concerned that modified men, or even infertile men, do not perform as well as wild-type mosquitoes in terms of reproduction," says Laura Harrington, an entomologist at Cornell University. Harrington, who studies mosquitoes, said she would not want governments to invest money in this solution in the absence of publicly available evidence.
As for the study, Harrington says the researchers could have designed their experience more carefully. "I think whenever possible, it's good to think about what really happens to mosquitoes on the ground," she says. In this environment, they will not be kept at a comfortable temperature of 57.2 degrees Fahrenheit and will be subject to other factors such as wind and rain. Without further testing, it's impossible to know how they will fend in real-life conditions – and beyond that, she notes that the strain of mosquito used in the experiment is high in the laboratory, not a wild strain or a cross, shown to be more reproductively successful.
"The fact that they can fly in an insect cage on a table is a pretty low bar," says Texas entomologist A & M University's Zach Adelman. "But it's a bar." With more studies, this shipping method may work. But there are bigger questions to answer about the effectiveness of any method of mosquito prevention, he says. There is no reliable scientific evidence as to whether pesticides, sterile insect technique or other strategies actually produce the desired results.
"I'm surprised how many people have been able to get into a tube," he says.