80% Of Disease-Carrying Mosquitoes Wiped Out

In an experiment with global implications, Australian scientists have successfully wiped out more than 80% of disease-carrying mosquitoes in trial locations across north Queensland. The experiment, conducted by scientists from the Commonwealth Scientific and Industrial Research Organization (CSIRO) and James Cook University (JCU), targeted Aedes aegypti mosquitoes, which spread deadly diseases such as dengue fever and Zika.

In JCU laboratories, researchers bred almost 20 million mosquitoes, infecting males with bacteria that made them sterile. Then, last summer, they released over three million of them in three towns on the Cassowary Coast. The sterile male mosquitoes didn’t bite or spread disease, but when they mated with wild females, the resulting eggs didn’t hatch, and the population crashed. “The invasive Aedes aegypti mosquito is one of the world’s most dangerous pests,” said CSIRO Director of Health and Biosecurity Rob Grenfell in a statement, describing the experiment as a victory. “Although the majority of mosquitoes don’t spread diseases, the three most deadly types — the Aedes, Anopheles and Culex — are found almost all over the world and are responsible for around (17%) of infectious disease transmissions globally.” The successful experiment offers a potential new solution for diseases which infect millions every year. Many mosquito-spread diseases are difficult to treat. Some don’t have effective vaccines, pesticides can be unsustainable, and methods such as clearing standing water are inefficient against mosquito breeding rates. The Zika virus is an infamous example. Its explosive outbreak in 2015 infected millions worldwide, causing babies to be born with neurological disorders. Researchers raced to develop a vaccine, and many are still conducting trials.

The experiment

Although the process used in the experiment, called the Sterile Insect Technique, has been around since the 1950s, it has never been used for mosquitoes like the Aedes aegypti. “We learned a lot from collaborating on this first tropical trial and we’re excited to see how this approach might be applied in other regions where Aedes aegypti poses a threat to life and health,” Kyran Staunton from James Cook University said in a statement. Scientists in the Cairns region of Australia have also used similar techniques to replace populations with mosquitoes that couldn’t spread infections, according to ABC News. This CSIRO-JCU experiment, however, aimed to eradicate those populations, working in partnership with Verily, a health research organization owned by Google parent Alphabet. Since the Aedes aegypti is an invasive species native to Africa, wiping them out in Australia wouldn’t do much ecological damage in the country. “The main ecological impact would be to restore the ecosystem to how it was before the mosquitoes invaded,” according to Verily. The experiment has been limited to north Queensland for now, but Verily may hold further field trials, the organization said.

Credit: Jessie Yeung for CNN, 10 July 2018.