Hacking mosquitoes to save lives
Mosquitoes cause more human suffering than any other insect, including nearly half a million deaths annually from malaria alone, the World Health Organization (WHO) reports.
Past efforts to stop mosquito-borne diseases have had limited success. That’s why public health experts worldwide are cautiously optimistic about a new approach, tested recently in Fresno, California, the state’s fifth-largest city, and Queensland, Australia, that country’s third most-populous state.
The new strategy is the brainchild of scientists at Verily, the life sciences research and engineering company of Alphabet Inc., parent company of Google.
The company’s big idea is to “hack” and eradicate disease-bearing mosquitoes by releasing millions of sterile males (males don’t bite) in areas where the insects are a problem. The males then mate with native females, but the eggs don’t hatch. As a result, the mosquito population declines over time.
That’s what the company did last year and the results are noteworthy. In Fresno, for example, the number of female aedes aegypti mosquitoes (females are the biters) decreased 68 percent last year in the release areas compared to similar “control” neighborhoods. The experiment was repeated again this summer using improved techniques, but the results are not yet available.
The experiment also was conducted in Queensland during its 2017-18 mosquito season. Results reported in July found the population of female aedes aegypti mosquitoes dropped by more than 80 percent relative to similar untreated areas. The Queensland experiment was significant because it showed that the new approach could be effective in tropical climates, where mosquitoes naturally thrive.
Only about 100 of the 3,500 species of mosquitoes spread disease to humans. So the initial company effort targeted one of the worst species, which is responsible for spreading dengue fever, yellow fever, and the Chikungunya and Zika viruses. Mosquitoes also transmit encephalitis, West Nile Virus, and a variety of diseases and parasites that afflict dogs, horses and livestock.
The big killer, of course, is malaria. The WHO reports that malaria alone kills one child every two minutes, most of them in Africa. There are 200 million to 300 million new cases globally each year. The incidence of new cases is one of 18 indicators of human well-being tracked by the Gates Foundation Goalkeepers report. The benefits of a successful mosquito “hack” would be revolutionary.
Traditional approaches to mosquito control include protective nets and government-run spraying programs, which started in the early 1900s and have been controversial since Rachel Carson’s 1962 book, “Silent Spring,” linked pesticide use to various health and environmental problems. Insecticides have improved since then, but the basic approach remains the same: kill mosquitoes with deadly insecticides.
Verily’s most difficult challenge, company officials say, is producing enough sterile males. The company has spent millions of dollars building a lab that breeds, raises, sterilizes and sorts by gender millions of mosquitoes.
Not everyone is enthusiastic about the new approach. Critics warn of disruption to the food chain from eradication. But Verily argues that aedes aegypti — native only to parts of Africa, invasive everywhere else — is not a critical part of any animal’s diet and does not pollinate crops.
Hacking pests could be a turning point in defeating some deadly diseases and saving millions of lives worldwide. It could also end the need for conventional spraying campaigns.
Victory appears increasingly possible. Smithsonian Magazine reported in August that the World Mosquito Program at Monash University, Melbourne, Australia, has used the sterile insect technique (SIT) to stop all outbreaks of dengue fever in the tropical city of Townsville, Queensland, for four years. Similar field studies continue elsewhere around the world.
Scientists and entrepreneurs using modern technology are creating a blueprint for ending an age-old pest that up to now has proven deadly and impossible to stop.
Private foundations and other NGOs focused on global health could take the next step by paying for a series of regional “inoculations” to permanently eradicate the 100 species of disease-carrying mosquitoes and diminish, if not end, associated diseases.
The days of harmful mosquitoes are hopefully numbered and with them the illnesses that have killed generations of children and ravaged countries around the world.