Suicide mozzies!


Dengue fever is prevalent in tropical climates, so we have our fair share, as can be seen by the number of patients we see with Dengue Fever at the Bangkok Hospital Pattaya, including some with the potentially deadly Dengue Hemorrhagic Fever.

Queensland in Australia has a similar climate and similarly has the dengue carrier, the mosquito.

Up till now we do not have much defense against the dengue carrying breed of mosquito, but news has just come out about scientists in Townsville (Queensland) who say they have promising results from their bold trial designed to eradicate the deadly mosquito-borne disease.

The trial has involved the release of millions of specially bred mosquitoes across the North Queensland city. These mozzies are specially bred mosquitoes and carry the wolbachia bacteria which makes them less likely to transmit the dengue virus.

Scientists had hoped the mosquitoes being released would pass on the bacteria, leading to the eradication of the deadly virus – dengue kills more than 10,000 people every year worldwide.

Over the past seven months, more than 2,000 Townsville residents have had a container placed in their backyards.

One of those backyards belongs to one lady resident who said, “I’ve had kids growing up in North Queensland all their life and there’s always mosquitoes biting. You always have the fear that they’re going to get something else along the line with dengue or Ross River or those sort of things. So anything that I can do to help to eliminate, I’m more than ready to do so.”

The Eliminate Dengue project is being run by a team of international researchers, including scientists from James Cook University and Melbourne University and has the backing from the Australian and Brazilian governments as well as groups such as the Bill and Melinda Gates Foundation.

The latest results show the trial is working as planned. Dr Andrew Turley is the field trial manager for the Eliminate Dengue program who said, “So what we’re seeing at the moment is we’re seeing the spread of the wolbachia bacteria increase and we’re seeing the frequency, sorry how common this bacteria is in the local mosquito population increase over time.”

It has now been reported that data shows that in the suburbs where the insects were initially released, up to 80 percent of mosquitoes now carry the bacteria.

The local city council is excited about the interim results. Gary Eddiehausen is a local councilor and sits on the project’s reference group. “Dengue fever affects nearly 400 million people a year right throughout the world and if this trial is successful, it’s certainly very exciting for what can happen right across the world in the future and reduce and if not totally get rid of dengue fever across the world.”

This was backed up by Dr Turley from Eliminate Dengue who indicated that while there are still years of analysis and research that needs to be done, the results show the project can be replicated across the country and the world.

Dr Turley said, “All our of previous field trials both in Australia and in different field sites around the world have always focused on sort of small individual suburb-wide trials whereas this is the first time where we’ve done a large chunk basically a city-wide, or a large, it’s basically the inner city area of Townsville we’ve done a release in within only a few months period.

“So it’s really encouraging that potentially using wolbachia could be applied to some of these large cities around the world where the dengue version is much higher than what we have here in Australia.”

Whilst this is encouraging, it reminds me of mxomatosis being used to control rabbits in Australia. A full-scale release was performed in 1950. It was devastatingly effective, reducing the estimated rabbit population from 600 million to 100 million in two years. However, the rabbits remaining alive were those least affected by the disease. Genetic resistance to myxomatosis was observed soon after the first release and most rabbits acquired partial immunity in the first two decades. Resistance has been increasing slowly since the 1970’s, and the disease now only kills about 50 percent of infected rabbits.

Will wolbachia bacteria be the same?