Why are thousands of mosquitoes being released in Washington DC?

Hundreds of thousands of mosquitoes are being released across the Washington DC area this summer – but the aim is to reduce, not increase, mosquito numbers.

Around 600,000 male mosquitoes carrying a naturally occurring bacteria called Wolbachia are being released as part of an innovative pest control programme. Because only male mosquitoes are used, they do not bite humans or feed on blood.

When these males mate with wild female mosquitoes, the Wolbachia bacteria prevents the eggs from hatching. Over time, this reduces the local mosquito population without the need for large amounts of chemical insecticides.

The programme is being carried out by Bee Safe Mosquito Control, becoming one of the first private companies in the United States to offer the technology directly to homeowners. Similar projects have previously been managed mainly by public health authorities and scientific research organisations.

The approach is gaining interest worldwide as scientists look for safer and more environmentally friendly ways to control mosquitoes that can spread diseases such as dengue fever, Zika virus and West Nile virus.

Interest in the technology is also growing because climate change is creating warmer conditions that allow mosquitoes to survive and reproduce in more places for longer periods of the year.

Meanwhile, Alphabet, the parent company of Google, is seeking approval to release up to 64 million Wolbachia-infected mosquitoes in parts of California and Florida as part of larger mosquito control projects.

Researchers say the technique could become an important tool in protecting public health while reducing reliance on pesticides, although monitoring will continue to ensure the programmes remain safe and effective.