California scientists unlock new key to mosquito-borne disease spread

Male mosquitoes that fail to hear potential females do not end up mating — a phenomenon that could have major implications for insect-borne disease spread, a new study has determined.

The mating process for mosquitoes occurs midair and lasts for just a few seconds, after a male insect responds to the sound of a female's wingbeats, according to the study, published on Monday in the Proceedings of the National Academy of Sciences.

When the study authors removed a single gene, called trpVA, to render the male mosquitoes deaf, they found that they had killed the insects' libidos entirely.

“You could leave them together with the females for days, and they will not mate,” senior author Craig Montell, a neurobiology professor at the University of California Santa Barbara, said in a statement.

These findings, the scientists stressed, could have major effects on how people control problematic mosquito vectors like Aedes aegypti, which infect hundreds of millions of people with disease-causing viruses every year.

The researchers suspected that hearing played a role in mosquito mating behavior after observing the courtship routines for Aedes aegypti — mosquitoes that spread diseases like dengue, Zika and yellow fever.

Females flap their wings at around 500 Hz, after which males take off and start buzzing at about 800 Hz — rapidly modulating this frequency when the females are nearby, per the study.

Following a quick midair meeting, they go their separate ways and males scout out new partners, the scientists noted.

“On summer evenings, we often see swarms of mosquitoes gathered by the water or under streetlights," co-lead author Yijin Wang, a former postdoctoral scholar at UC Santa Barbara, said in a statement.

"These gatherings are essentially mass mating events,” Wang added.

Investigating the insect's auditory neurons and sensory apparatuses, the team focused on a specific channel called TRPVa and its corresponding gene, trpVA.

Using a CRISPR gene editing technique, the scientists knocked out the trpVa gene and thereby caused the males mosquitoes to stop reacting to sound. And when they placed the deaf males in chambers with females, they found that nothing happened.

“If they can’t hear the female wingbeat, they’re not interested,” Montell said.

Because pathogens spread by the Aedes aegypti mosquitoes infect some 400 million people each year — with about a quarter developing related diseases — understanding how to disrupt mosquito lifecycles could provide important insights into disease prevention, according to the authors.

One current method used for mosquito control is called the sterile insect technique, which works by releasing many sterile males to mate with females, who tend to mate with only one partner.

But the success of this technique is limited by the competitiveness of sterile males, as they must reach the females before fertile males do so, the authors explained.

While this method hasn't led to sufficient suppression of mosquito populations, the study authors expressed hope that their gene editing strategy might help increase its effectiveness.