How making mosquitoes deaf can stop spread of dengue, Zika, yellow fever

Researchers have found a novel method to stop the spread of diseases such as dengue, Zika, and yellow fever by making mosquitoes deaf.

In Short

• Making male mosquitoes "deaf" disrupts their ability to mate
• This could slow the spread of diseases like dengue, Zika and yellow fever
• This can happen by silencing a single gene responsible for hearing

Researchers have discovered a unique way to prevent the spread of diseases like dengue, Zika, and yellow fever—by making mosquitoes deaf.

The primary carriers of these viruses are Aedes aegypti mosquitoes, which spread disease through their bites. According to a recent study, silencing the hearing of male mosquitoes disrupts their ability to mate, potentially slowing the spread of these vector-borne illnesses.

This approach sheds light on the essential role of hearing in mosquito mating. Researchers in Professor Craig Montell's lab found that when male mosquitoes lose their hearing, they show no interest in mating with females. Normally, mating occurs midair, triggered by the distinctive sound of female wingbeats, which the males can detect as a signal to pursue them.

By disrupting this auditory cue, scientists hope to reduce mosquito populations and curb the transmission of these dangerous diseases.

"The absence of a single gene, trpVa, produced this profound effect on mosquito mating behaviour," explained co-lead author Dhananjay Thakur, a postdoctoral scholar in the Department of Molecular, Cellular, and Developmental Biology.

Female mosquitoes flap their wings at about 500 Hz, which attracts nearby males. When the males hear this sound, they start buzzing at a higher pitch of around 800 Hz and adjust their frequency quickly to match.

This leads to a brief midair meeting, after which they separate. While males are constantly on the lookout for new mates, a female usually won’t mate again after a successful encounter.

The team from the University of California, Santa Barbara used CRISPR-Cas9 to knock out the gene that codes for TRPVa in Aedes aegypti mosquitoes. The resulting animals showed no reaction to sound.

In fact, they found that sound elicited no electrical activity from neurons in the Johnston’s organ. The insects were truly deaf.

The sterile insect technique (SIT) is a promising way to control insect vectors by releasing sterile males to mate with females, preventing them from reproducing.

This method has proven effective for agricultural pests like the California medfly, which was a major problem 30 years ago before SIT helped control it.

However, SIT’s success with Aedes aegypti mosquitoes is limited because sterile males must reach the females before natural males.

Montell's lab is now exploring ways to make sterile males more competitive, possibly by targeting mosquito hearing to enhance SIT’s impact on mosquito populations.