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Infecting dengue-carrying mosquitoes with a natural strain of bacteria can dramatically reduce their numbers, new research from Australia shows.
In a trial in three communities in northern Queensland, researchers significantly suppressed populations of Aedes aegypti mosquito that spreads dengue, Zika, chikungunya and other viruses.
The trial was conducted with local approval in the towns of Mourilyan and South Johnstone in far north Queensland, as well as in Goondi Bend, a suburb outside Innisfail.
For 20 weeks, scientists in Queensland, working with Verily Life Sciences – a research company owned by parent company Google Alphabet – released 3 million male mosquitoes infected with a bacteria known as Wolbachia.
At the three test sites, mosquito populations then fell by more than 80%.
In Mourilyan, where suppression was most successful, the team returned the following year to find that the mosquitoes had all but been wiped out, with a 97% reduction in the population.
The trial began in 2018 and was documented in a study published Tuesday in the peer-reviewed journal PNAS.
CSIRO scientist Nigel Beebe, lead author of the study, said that the infection of men Aedes aegypti mosquitoes – which do not bite – with the bacteria appeared to alter certain components of their reproductive biology.
Wild female mosquitoes that mate with infected males therefore lay eggs that never hatch.
“Wolbachia is one of those bacteria that is found in many insects, ”said Beebe, who is also an associate professor at the University of Queensland. “It is a very good sterility agent; it does not affect the physical form of the mosquito much.
Aedes aegypti – also known as the yellow fever mosquito – arrived in Australia over a century ago. It is largely confined to Queensland, although earlier this year the mosquito was detected in the Northern Territory.
Removing its number would likely not have major negative ecological effects, Beebe said.
“It only exists in urban landscapes. It bites humans preferentially, like 95% of the time. The cityscape is a pretty artificial ecosystem, so removing a mosquito from that ecosystem is unlikely to be a problem. “
The Aedes aegypti The mosquito is found in the tropics of more than 120 countries and infects millions of people around the world with viruses every year. The number of dengue cases reported to the World Health Organization has increased more than eightfold globally over the past two decades.
Researchers have already infected Aedes aegypti mosquitoes with different strains of Wolbachia bacteria to reduce the likelihood of mosquitoes transmitting viruses that affect humans.
A Global Mosquito Program trial in Indonesia last year found that mosquito infection with the bacteria reduced the number of dengue infections in Yogyakarta city by 77% compared to untreated areas. An earlier trial in Townsville found that the technique was successful in preventing dengue outbreaks.
In these studies, both male and female mosquitoes were infected with the bacteria.
Wolbachia is unlikely to have an effect if a human is bitten by an infected female mosquito, Beebe said. “There is both experimental and observational evidence that these Wolbachia [bacteria] cannot invade human cells.
The team plans to use a similar technique to suppress the Asian tiger mosquito that spreads the virus, Aedes albopictus, an “incredibly plague” species that has established itself in the Torres Strait Islands since 2004.
“We want to build our own sterile male system so that when this mosquito comes to the mainland, we can launch it,” Beebe said.
Mosquito control programs are also underway for other species in French Polynesia and the Hunter region of New South Wales.
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