Scientists uncover what makes blood so scrumptious for mosquitoes

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A team of scientists in the United States discovered what compounds in human blood attract mosquitoes – potentially paving the way for a drug that could mask our tempting tastes.

The insects are not attracted to simple aromas such as sweet or salty, but only to a complex combination of ingredients.

A team of researchers at Rockefeller University in New York City used genetically engineered women to determine which neurons fire when they taste blood.

Only female mosquitoes feed on the blood they need for their eggs to develop, but they mostly survive on nectar like thousands of other species of insects.

Their blood-sucking habits make them the deadliest animal on the planet for humans, killing around half a million people each year from diseases such as malaria, dengue fever, and yellow fever.

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The researchers got the mosquitoes to switch from the nectar-feeding mode to the blood-feeding mode by offering them a mixture of four compounds designed to mimic the taste of blood. It contained glucose, sodium chloride, sodium bicarbonate and adenosine triphosphate (ATP) – a compound that supplies cells with energy.

The mosquitoes loved this synthetic “blood”, but they weren’t interested in a mixture of sugar and saline.

A fluorescent marker in the genetically engineered insect glowed when a nerve cell was activated, so researchers could see which nerve cells lit up when they were offered different meals.

In particular, glucose, which is found in both nectar and blood, has not consistently activated neurons. Sodium chloride, sodium bicarbonate, and ATP each activated specific clusters of neurons.

However, a cluster of neurons was only activated by blood, including both real blood and the researchers’ synthetic mixture, and not by any of the ingredients separately.

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“These neurons break the rules of traditional taste coding, which is believed to be preserved from flies to humans,” said Veronica Jové, one of the lead researchers in the study.

Dr. Leslie Vosshall, director of the laboratory at Rockefeller University’s Howard Hughes Medical Institute, said the investigation could eventually lead to oral mosquito repellants that would affect their blood taste. But she said it was impossible to ever understand exactly how people taste of mosquitoes.

She compared it to trying to describe how a honey bee sees a flower in ultraviolet hues invisible to the human eye, or how bats see through sonar waves that we cannot hear. “There’s nothing like it in human experience,” she said.

Readers’ questions and answers: Why do mosquito bites itch so much?

Asked by: Duncan Borg Conti, Malta

When a mosquito bites, it injects saliva, which contains anticoagulant enzymes, into the wound. The first time you’re bitten, nothing happens, but your immune system then starts making antibodies that bind to these foreign proteins.

For a while, this immune response will cause itchy, swollen bumps. Over many years this reaction will fade, but if you are not bitten for a long time, it may start again next time.

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