Nguyen Thi Yen rolls up the sleeves of her lab coat and slips her arms into a box covered by mesh netting. Immediately, the feeding frenzy begins. Hundreds of mosquitoes light on her thin forearms and swarm her fingers. They spit, bite and suck until becoming drunk with blood. Yen laughs in delight while her so-called “pets” enjoy their lunch and prepare to mate.
She smiles and nods at her red arms, swollen and itchy after 10 minutes of feeding. She knows those nasty bites could reveal a way to greatly reduce one of world’s most menacing infectious diseases.
All her mosquitoes have been intentionally infected with bacteria called Wolbachia, which essentially blocks them from getting dengue. And if they can’t get it, they can’t spread it to people.
New research suggests some 390 million people are infected with the virus each year, most of them in Asia. That’s about one in every 18 people on Earth, and more than three times higher than the World Health Organisation’s previous estimates.
Known as “breakbone fever” because of the excruciating joint pain and hammer-pounding headaches it causes, the disease has no vaccine, cure or specific treatment. Most patients must simply suffer through days of raging fever, sweats and a bubbling rash. For those who develop a more serious form of illness, known as dengue haemorrhagic fever, internal bleeding, shock, organ failure and death can occur.
And it’s all caused by one bite from a female mosquito that’s transmitting the virus from another infected person.
So how can simple bacteria break this cycle? Wolbachia is commonly found in many insects, including fruit flies. But it is not carried naturally by certain mosquitoes, including the most common one that transmits dengue, the Aedes aegypti.
The germ has fascinated scientist Scott O’Neill his entire career. He started working with it about two decades ago at Yale University. But it wasn’t until 2008, after returning to his native Australia, that he had his eureka moment.
One of his research students figured out how to implant the bacteria into a mosquito so it could be passed on to future generations. The initial hope was that it would shorten the insect’s life. But soon, a hidden benefit was discovered.
“The dengue virus couldn’t grow in the mosquito as well if Wolbachia was present,” says O’Neill, dean of science at Monash University, Melbourne.
O’Neill’s team conducted research in small communities in Australia, where dengue isn’t a problem, and