Bacteria breakthrough makes it faster and cheaper to develop 'safe' mosquitoes

Adding a type of bacteria to water where larvae grow speeds up their development

Genetically modified mosquitoes have been released in a bid to reduce the risk of deadly infections in humans. EPA

Scientists hope to rapidly increase the population of mosquitoes that cannot spread diseases after a breakthrough that could benefit mass breeding programmes.

Researchers at the University of Exeter have discovered a way to speed up mosquitoes' development, making it cheaper and quicker to farm them for release into the wild.

In control programmes, scientists genetically modify mosquitoes so they are either sterile or infected with a bacteria known as Wolbachia on the basis that the bacteria outcompetes viruses in their bodies, reducing the risk of deadly infections in humans. They are then released into the wild to mate with the biting females, which produce eggs that do not hatch, driving down the population of disease-carrying mosquitoes.

The new technique aids this process by speeding up the development of farmed mosquitoes. Working with the knowledge that some mosquitoes need bacteria to develop, scientists at the University of Exeter theorised that a particular species of bacteria – Asaia – could change the speed of the mosquitoes' growth.

When added to the water where the larvae develop, the bacteria led to an increase in their growth of 10 per cent, reducing the larval period from 10 days to nine, which could make it faster and cheaper to farm them.

“Very large-scale rearing has a number of logistical challenges,” Ben Raymond, professor of ecology and evolution at the University of Exeter, told The National. “Our experiments show that it’s possible to accelerate their development by around 10 per cent and so provide a significant cost saving for medical organisations involved in mass rearing.”

Prof Raymond said it is easy to culture the bacteria and only a small amount is needed to produce the effect. The scientists think the results would be reproduced in other places since they duplicated results in a second laboratory with different strains of mosquito. “So we think these results are robust,” he said. But there are some unknowns.

“Nevertheless, I would encourage anyone to check effects in local conditions,” he said. One specific unknown is whether or not the new bacteria will interact with the Wolbachia involved in reducing disease transmission, he added.

“The bacteria compete in malaria mosquitoes in the adults and it’s possible they may compete in [Aedes aegypti] mosquitoes also, although the context here is quite different as Asaia don’t persist beyond the larval stage and colonise adults in our experiments,” he said.

A recent study found that climate change is placing more people at risk of mosquito-borne diseases such as dengue fever, extending the seasonal window and creating frequent outbreaks that will become increasingly difficult to deal with.

The warning, shared in April, came after a report by The National revealed that global cases of dengue had risen sharply, with several Arab nations in particular experiencing an increase. Medics in Dubai said although the number of patients infected with the debilitating tropical disease requiring care was low, several cases had been reported to health authorities.