In the space of only two years, scientists have virtually wiped-out the most invasive mosquito in the world from two islands in the Chinese city of Guangzhou.
The mosquito species, also known as the Asian tiger (Aedes albopictus), is a carrier of dangerous infectious diseases such as Zika, dengue, and chikungunya, which affect millions of people worldwide. Also, the insect is notoriously difficult to control.
Over the past 40 years alone, the wily blood-sucker has spread from its original home in Asia to every other continent on the planet, excluding Antarctica. With limited vaccines and drug treatments for the diseases that it transmits, the mosquito's impact on public health has been disproportionate to its tiny size.
An exciting field test of an innovative mosquito control technique shows we have the potential to change all of that. By combining two existing methods, scientists reduced Asian tiger mosquito populations by up to 94% on two river islands in China. In some cases, not a single viable egg was found for up to 13 weeks.
In a recent review of the work, Peter Armbruster, a mosquito ecologist at Georgetown University, said that the results were "remarkable" and that they show the "potential of a potent new tool in the fight against mosquito-borne infectious disease."
The two-pronged approach includes a dose of radiation that sterilizes the mosquitoes, and a bacterial strain from the Wolbachia genus, that prevents the mosquito eggs from hatching. Together, when those two methods are applied to lab-grown mosquitoes, they seem to work much more effectively than on their own.
According to Science Alert, current radiation-based techniques work by releasing sterile male insects into the environment, so they breed with females (that only mate once), decreasing the overall size of their population. The issue is, irradiation tends to make these males less competitive sexually and also more likely to die.
Other methods which use bacteria to reduce offspring are less harmful to the individual mosquito, but they only work if the lab-grown male is infected and not the wild female. If both the male and female have the bacterial infection, they will have no issue producing healthy offspring, making it a delicate balancing act.
As you can imagine, sifting through male and female insects in the lab is painstaking business, and even when scientists go to all this effort, the accidental release of Wolbachia-infected females happens approximately 0.3% of the time, undermining the entire mission.
Therefore, the new solution rears Wolbachia-infected mosquitoes in the lab and then subjects them to low levels of radiation, effectively sterilizing any included females while leaving the males still able to reproduce.
Not only does that sound great in theory, it also seems to work in practice. By getting rid of the need for sex testing, the group could produce and release large numbers of those lab-grown mosquitoes - around two hundred million in total - in a city with the highest dengue transmission rate in China.
After two years, their findings demonstrate an approximately 97% decline in mosquito bites suffered by locals on the two islands. Plus, every year, the average number of wild-type adult females caught per trap dropped by 83% to 94%, with none detected for up to six weeks.
The few mosquitoes which remain on the island probably migrated from outside the study area, according to the authors. And while this suggests that the region will not be mosquito-free for long, if the technique can be implemented on a larger scale, it could create a place free from Asian tiger mosquitoes and the deadly diseases they carry.
The study has been published in Nature.
COMMENTS