Insects unable to transmit viruses halted disease in Australian city –
now scientists hope same technique could help tackle Zika and malaria
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 https://www.theguardian.com/world/zika-virus" rel="nofollow - 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 https://www.worldmosquitoprogram.org/" rel="nofollow - 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 https://gatesopenresearch.org/" rel="nofollow - 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.
Source: https://www.theguardian.com/society/2018/aug/01/dengue-fever-outbreak-halted-by-release-of-infected-mosquitoes" rel="nofollow - https://www.theguardian.com/society/2018/aug/01/dengue-fever-outbreak-halted-by-release-of-infected-mosquitoes