‘Good’ mosquitoes join disease battle

A British biotech company has become the first to sell genetically modified mosquitoes with a ‘‘suicide gene’’ directly to the public, to help combat diseases such as dengue fever.

The insects have been developed by Oxitec, a company founded by Oxford University scientists and based in Abingdon, England. People in Brazil can order eggs online which produce genetically altered males of the Aedes aegypti mosquito.

The males do not bite, so they don’t spread disease. When they breed with wild females – which do bite – the female offspring carry a lethal gene that causes their bodies to be flooded with a toxic protein that kills them before they reach adulthood.

This genetic ‘‘kill switch’’ should remain in the population for about 10 generations, equivalent to about 10 months, suppressing mosquito numbers and reducing rates of dengue and other diseases they carry.

The insects have been fitted with a second gene that makes them fluorescent, allowing them to be tracked.

‘‘These are good mosquitoes that control bad mosquitoes,’’ said Oxitec chief executive Grey Frandsen.

Traditional controls such as insecticides were losing effectiveness as the insects developed resistance, he said. ‘‘It’s been a long road to get to this point, but this is an exceptionally powerful technology and completely safe.’’

The World Health Organisation says rates of dengue have grown dramatically, with about half the global population at risk. Up to 400 million people a year are infected, many of them children.

Tests in a region of Brazil that had been racked with the disease suggested in 2016 that Oxitec’s mosquitoes could cut cases by more than 90 per cent.

The Aedes aegypti mosquito also carries the Zika virus, which causes babies to be born with tiny heads and damaged brains, as well as chikungunya, another viral infection that has spread around the world, partly due to climate change.

The same genetic tactics could also be used to tackle agricultural pests and female Anopheles mosquitoes, which carry the most dangerous form of malaria, which kills about 500,000 people a year.

‘‘We have two malariatransmitting mosquitoes that we’re working on,’’ Frandsen said.

In Brazil, the Oxitec mosquitoes are being sold in the state of Sao Paulo for about US$10 to US$30 (NZ$15 to $45) a month through a subscription service. Customers get a box of eggs to put in a garden or balcony. Egg refill packs are delivered by post.