In the final instalment of our summer showcase of case studies from our report, Celebrating UK Bioscience, today we take a look at the story behind Oxitec’s genetically engineered mosquitoes and how they are battling mosquito-borne diseases around the world.
The danger of the status quo – why we need new interventions to battle mosquito-borne diseases
Mosquitoes are the most dangerous creature in the world. They kill one person every 12 seconds and infect hundreds of millions of people each year with serious diseases. Aedes aegypti is a particularly harmful species because it mainly bites people and it lives in and around homes. The tendency of the biting females to hide in nooks and crannies around the home makes it remarkably difficult to reach those hiding places. This mosquito is also developing resistance to the chemicals used to kill it.
Ae. aegypti can carry serious diseases including dengue, chikungunya and Zika viruses, so without more effective ways to control these mosquitoes, the public health implications are stark. Even world-leading mosquito control groups with fleets of planes and helicopters can only reduce Ae. aegypti by about 50%. With that many disease vectors still around, it is possible for these serious diseases to be introduced and reintroduced at any time. With no cure or available vaccine for either dengue fever or chikungunya, the World Health Organisation recommends controlling the mosquito itself.
How Oxitec’s mosquitoes are providing a new way forward
The battle against mosquito-borne diseases can be fought on multiple fronts. Companies are racing to find working vaccines and to test them in clinical trials to determine whether they will work. But viruses mutate and new strains appear. A compatible but different approach is to reduce the numbers of mosquitoes spreading the disease below the transmission threshold, so that whatever the virus does, there simply aren’t enough mosquitoes around to spread it.
UK biotech company Oxitec, which was spun out of Oxford University in 2002, does exactly that by using genetically engineered mosquitoes to control their own species. Oxitec mosquitoes are genetically engineered so their offspring die before they can reproduce and before they can become transmitters of disease. It’s an approach similar to the Sterile Insect Technique (SIT) where male insects are sterilised by radiation and released to mate with pest females. With successive releases there are fewer offspring each generation and the pest population crashes.
The Oxitec mosquito is inspired by the SIT approach but doesn’t rely on radiation, which can affect many genes and the insect’s competitiveness. Instead, Oxitec uses just one gene to induce ‘sterility’ and a colour marker gene for monitoring the results. Like SIT, this approach requires successive releases, but there are major environmental benefits such as the disappearance of the engineered insects and their genes from the environment once releases are stopped. The approach is also species-specific, controlling only the non-native Ae. aegypti, so other native species can flourish.
Since trials started in 2009, Oxitec has reduced target Ae. aegypti populations by more than 90%. This is an unprecedented level of control and is a key reason why mosquito control groups around the world are keen to evaluate it for use in their countries. Another reason is its light ecological footprint because it’s a highly targeted control method that is non-toxic and pesticide-free.
Success to date and ambitions for the future
Since 2009, mosquito trials have been completed in Cayman, Malaysia, Brazil and Panama, without adverse effects on people or the environment, and more projects are being planned. The Oxitec mosquito has been rigorously evaluated both scientifically and by regulators in multiple countries with laboratory studies, cage studies, and field studies of increasing size.
This evaluation process for new control methods is vital to progress in the war against mosquitoes, and an important consideration for such evaluations is weighing the potential risks of a new intervention against the risks of maintaining the status quo.
In Brazil, the dengue burden is so great that they’ve called in the army to help educate people on how to fight the Ae. aegypti mosquito. Brazil has a lot of experience and expertise in tackling dengue and recognises the need for new approaches to complement and improve on current methods. This forward thinking has led to the first municipal project of genetically engineered mosquito control following approval by the national biosafety group (CTNBio) for release of Oxitec mosquitoes throughout the country. The city leading the way is Piracicaba, in São Paulo state.
The hope is to build on the success of the Oxitec mosquito to tackle the mosquitoes that transmit malaria next.
The lead inventor of the Oxitec mosquito was also the UK’s sole nominee for a prestigious international award for this biotechnology breakthrough in battling disease-carrying mosquitoes. Named one of the top 20 European inventors, award nominee, Dr Luke Alphey, also hopes to inspire the next generation of scientists to carry on this important work, and join in the fight against vector-borne disease.
Like to find out more? You can read the full version of the above story, along with five other case studies, in our report, “Celebrating UK bioscience: unravelling the stories behind UK bioscience success”.