Image copyright Peter Illiciev/Fiocruz Image caption The specially bred mosquitoes carry the bacteria Wolbachia which reduces the transmission of viruses

Australian researchers say for the first time an entire city has been protected from viral disease dengue.

Captive-bred mosquitoes with a naturally occurring bacteria were released in the city of Townsville, where they mated with local mosquitoes.

By spreading the bacteria Wolbachia, which hinders dengue transmission, the city has been dengue-free since 2014.

Researchers from Monash University also believe their work could stop mosquito-borne diseases Zika and malaria.

"Nothing we've got is slowing these diseases down - they are getting worse," said Scott O'Neill, director of the World Mosquito Program, quoted by the Guardian.

"I think we've got something here that's going to have a significant impact and I think this study is the first indication that it's looking very promising."

Over four monsoon seasons, researchers released the Wolbachia-carrying mosquitoes across 66km sq (25 sq miles) in the Queensland tropical town of 187,000 people.

The community embraced the project, with even school children releasing the special mosquitoes that passed on their bacteria to the local population of mosquitoes.

Media playback is unsupported on your device Media caption The 'magic box' that could help beat malaria

They have published their results, calling the trial the first citywide success.

"At a cost of around A$15 (£8.50) per person, the Townsville trial demonstrates the approach can be rolled out quickly, efficiently and cost effectively to help provide communities ongoing protection from mosquito-borne diseases," Professor O'Neill said.

The programme is currently working in 11 countries and aims to deploy the Wolbachia mosquitoes in larger and poorer parts around the world with a target of reducing the cost to just US$1 (75p) per person.

The next step for the team is in Yogyakarta in Indonesia - a city of nearly 390,000 - where a randomised controlled trial is under way.</s>The first large-scale deployment of mosquitoes infected with Wolbachia bacteria, which makes them unable to transmit viruses, has stopped all outbreaks of dengue fever in a city in northern Australia for the last four years.

The success of the project in Townsville, Queensland, will encourage hopes that Wolbachia can provide a knockout blow against the Zika virus in Brazil as well, where the mosquitoes have been introduced into the favelas of Rio de Janeiro. Until now, the technology has looked promising but has only been tried in small pilot projects around the world of 1 to 1.5 square km.

Townsville, however, with 187,000 inhabitants, is on a much larger scale. Mosquitoes specially bred to carry Wolbachia, which occurs naturally in up to 60% of insects, were let loose over 66 square kilometres of the city in places where they could naturally breed.

In four rainy seasons since the mosquitoes were introduced, dengue has ceased to be a problem in Townsville, which has had no cases of a disease that used to be troublesome.

“I’m ecstatic,” said Scott O’Neill, director of the World Mosquito Program at Monash University in Australia, who led the project. “After a long slog in my career in doing this, I think this is a piece of work I’m really quite proud of because it really shows we’ll be able to take this all the way, I think.

“We’re wanting to have a really major impact on disease. For dengue and Zika nothing’s working at the moment for control. There’s evidence of a growing disease burden and there was the big Zika pandemic that stripped through the Americas recently and the rest of the world.

“Nothing we’ve got is slowing these diseases down – they are getting worse. I think we’ve got something here that’s going to have a significant impact and I think this study is the first indication that it’s looking very promising.”

The people of Townsville accepted the project – and even took part in it, with schoolchildren releasing the mosquitos. Community ownership is important, said O’Neill. Communities involved in projects in Rio de Janeiro in Brazil, Medellin in Colombia, and Indonesia have all embraced the work, possibly because of the fear of the diseases they are trying to control, said O’Neill.

The results of the Townsville project are being published on the Gates Open Research site, set up by the programme’s biggest funder. The next big test will be in Yogyakarta in Indonesia, where O’Neill and colleagues are conducting a randomised controlled trial. This will compare areas of a city where Wolbachia mosquitos are introduced with other areas where they are not. They will track the disease burden in each and provide important scientific evidence as to efficacy.

The programme is now in 11 other countries. The land area covered in Rio is twice that of Townsville and the population six times as great, with more than 1.5 million people. “Rio is one of the hardest places to work in,” said Scott. “The favelas are quite a challenge. If we can be successful in Rio we can probably be successful anywhere in the world.”

The cost of the programme was AUD$15 (£8.50) per inhabitant in Townsville, but the team hope it can be made available for USD$1 (75p) each in cities in poorer parts of the world.

There does not appear to be an environmental downside to the release of Wolbachia-carrying mosquitos, he said, and he believes the technology is safe. “If there is one thing that keeps me up at night, it’s how long and how strongly the effect will last – whether there will be an attenuation over time,” he said. But there have been Wolbachia mosquitos in the field for seven years now and the effect does not appear to have waned yet.

In the long run, if Wolbachia does prove safe and effective, scientists may attempt its use against malaria. In 2016, there were 216 million cases of malaria worldwide and 445,000 deaths. “There is lab data showing this approach could be effective in malaria as well, but that is much further upstream,” said O’Neill.</s>The first large-scale release of mosquitoes engineered to be incapable of transmitting diseases has proved successful in halting dengue fever outbreaks in a city in northern Australia. The mosquitos are infected with Wolbachia bacteria, a natural bacteria occurring in 60 percent of all insect species, that reduces their ability to transmit diseases to humans.

The project, which took place in Townsville, Queensland, involved the deployment of specially bred mosquitos across 66 kilometers of the city. Four rainy seasons have passed since their release and Townsville hasn’t seen a single case of dengue. The discovery has the potential to transform the fight against life-threatening mosquito-borne diseases, including the Zika virus and malaria, according to The Guardian.

Director of the World Mosquito Program at Monash University, Scott O’Neill, spoke to the success of the project, “I’m ecstatic. After a long slog in my career in doing this, I think this is a piece of work I’m really quite proud of because it really shows we’ll be able to take this all the way, I think.”

O’Neill added that the success of the Australian study may be the first indication that there is a solution for slowing down or halting mosquito-borne diseases, especially as previous efforts to do so have yet to make a major impact.

The project also saw large community participation, with schoolchildren involved in growing and releasing the mosquitos. The program has now spread to 11 other countries, with community projects taking place specifically in high-risk regions, including Rio de Janeiro in Brazil, Medellin in Colombia, and Indonesia.

In Rio de Janeiro, mosquitos have been released in the hope of targeting and eliminating the Zika virus. The results look promising but the experiment has only been conducted in small areas of the city.

As of now, O’Neill is confident that the technology for creating Wolbachia-carrying mosquitos is safe and does not prove to have any downsides for the environment. The mosquitos have been in the field for seven years and the effects have not slowed down, providing hope that the solution is long-lasting.

The next big project will take place in Yogyakarta, Indonesia, where O’Neill and his colleagues plan to conduct a randomized controlled trial to track the disease burden in areas with and without the presence of the Wolbachia-carrying mosquitos.

In the long run, the World Mosquito Program is aiming to use the mosquito technology to target other diseases, specifically malaria.

“There is lab data showing this approach could be effective in malaria as well, but that is much further upstream,” said O’Neill, as per The Guardian article.</s>Researchers are confident they've found a cost-effective and quick way for communities to protect themselves from mosquito-borne diseases.

Monash University says there hasn't been a single case of locally transmitted dengue fever in the past four rainy seasons in Townsville since mosquitoes carrying the Wolbachia bacteria were released in the north Queensland city.

The university's World Mosquito Program is investigating the practicality of using Wolbachia to prevent the spread of mosquito-borne diseases.

It has developed technology which shows the ability of Aedes aegypti mosquitoes to transmit diseases such as dengue, Zika and chikungunya is reduced when the naturally-occurring bacteria is introduced.

Mosquitoes carrying the bacteria pass on this ability after being introduced to local populations.

Program director Professor Scott O'Neill said the Townsville success showed the method was self-sustaining and cost-effective.

"At a cost of around $15 per person, the Townsville trial demonstrates the approach can be rolled out quickly, efficiently and cost effectively to help provide communities ongoing protection from mosquito-borne diseases," Professor O'Neill said.

The program now aims to deploy Wolbachia mosquitoes in larger cities around the world with a target of reducing the cost to just US$1 per person.

"Not only were communities accepting of the technology, but they also became active participants, with residents and local school students growing and releasing their own Wolbachia mosquitoes," Prof O'Neill said about the Townsville program.

"We believe our approach will be suitable for other cities, with appropriate local adaptation, and provides a framework for scaling-up our deployment, globally."
Researchers from Australia report the success of a plan to use mosquitoes infected with Wolbachia bacteria to prevent the spread of dengue fever in an Australian town, stating that they intend to bring the program to other locales.