The search for mosquitoes continues quickly and from different angles.
In two new studies, scientists report that they have revitalized an insecticide commonly used to kill malaria vectors and are learning what people taste like to one of the world’s most annoying insects.
In the first article published in the journal PNAS, New York University (NYU) researchers report that they made trace amounts of deltamethrin more effective by heating it to change its chemical structure.
Like many insecticides, deltamethrin comes in crystal form; When mosquitoes step on the crystals, the insecticide will be absorbed through their feet and, if effective, will kill them. However, it is facing increasing resistance in Anopheles mosquito populations.
As part of their research on crystal formation and growth, NYU’s Bart Kahr and Michael Ward heated the commercially available form of deltamethrin to 110 degrees Celsius for a few minutes and then allowed it to cool to room temperature. This resulted in a new crystallized form with long, tiny fibers radiating from a single point.
Tests on Anopheles quadrimaculatus and Aedes aegypti mosquitoes, as well as fruit flies, found that it works up to 12 times faster than the existing form. It also remained stable and therefore effective for at least three months.
The researchers – from NYU and the University of Puerto Rico – say epidemiological models show that less would have to be used to achieve the same effect, potentially lowering the cost of mosquito control programs and reducing environmental exposure to the insecticide.
In the second study, a team from Rockefeller University, USA, looked at genetically engineered mosquitoes, which fire neurons when they taste blood.
Female mosquitoes have finely tuned senses. Photo credit: Alex Wild.
“If mosquitoes couldn’t recognize the taste of blood, they couldn’t theoretically transmit disease,” says Veronica Jové, lead author of a paper in Neuron magazine.
Only female mosquitoes feed on blood that they need for their eggs to develop.
Jové therefore suspected that female Aedes aegypti mosquitoes, unlike men, could differentiate between blood and nectar based on taste.
Indeed, she found that women have two modes of feeding that use different mouth parts and recognize different flavors. A nectar-feeding mode detects sugar and a blood-feeding mode uses a syringe-like “stiletto” to pierce the skin and taste blood.
The researchers fed mosquitoes into blood nutrition by offering a mixture of four compounds: glucose (sugar), sodium chloride (salt), sodium bicarbonate (found in both blood and baking soda), and adenosine triphosphate, or ATP, a compound that provides energy to cells .
To see the taste neurons in action, the researchers genetically engineered mosquitoes with a fluorescent tag that glowed when a nerve cell was activated. They then observed which cells in the stiletto glow in response to different meals. Only a subset was activated by blood, including real blood and the researchers’ artificial mixture.
The hope, of course, is that a better understanding of mosquito senses will lead to new ways to prevent them from biting us.
Right now we know that a female mosquito can taste things we can’t. “There is nothing like it in human experience,” says co-author Leslie Vosshall.