Mosquitoes are the world’s deadliest animal. Infectious diseases, including malaria, are transmitted through female mosquitoes, which need a blood meal to produce eggs. According to the World Health Organization, there were an estimated 241 million cases of malaria in 2020, which resulted in 627,000 deaths. While nearly half of the world’s population is as at risk of being infected with malaria, an estimated 96% of associated deaths occur in sub-Saharan Africa. Children under 5 years old are the most vulnerable, accounting for 80% of these deaths.
Targeting Mosquitos With Technology
Wealthy countries can spray their way out of the problem. For example, Manatee County in Florida has an annual budget of $5.5 million for mosquito control, according to YourObserver.com. With about 400,000 residents, that’s $14 per person per year. That money pays for helicopters and pilots that fly over neighborhoods at night to spray insecticides. The goal is to spray female mosquitos as they buzz through the air looking for a blood meal. As a result of these efforts, mosquitos are mostly just a nuisance in Manatee County, although there have been recent outbreaks of mosquito-transmitted encephalitis, West Nile virus, and Zika virus. Wealthy countries also have more resources for treating malaria and other diseases.
In sub-Saharan Africa, a more economical approach is needed. One method that is proving to be effective is the use of drones — like the ones used by backyard hobbyists — connected to a smartphone app that identifies sites where mosquitos lay their eggs. Those same drones can be equipped to dispense insecticides quite precisely. By treating these sites before the mosquitos can mature and fly away, small amounts of insecticide can prevent the transmission of infectious diseases. This reduces the cost, the environmental impact, and the likelihood that the mosquitos become resistant to the insecticide. One recent study published in the American Journal of Entomology tested this approach in Uganda, where the GDP is about $800 per person per year.
Identifying Larval Habitats
Malaria is transmitted by Anopheles mosquitoes, which lay their eggs in stagnant water and typically take 10 to 14 days to develop from egg to larva to adult, according to the CDC. Some larval habitats are essentially permanent and easy to identify, such as marshes, mangrove swamps, and rice patties. Other larval habitats are temporary and small, such as rain pools at construction sites, in hoof prints, and in tire tracks on unpaved roads. There may be thousands of these sites within an acre of land after a heavy rain. Identifying and treating these sites would be very labor intensive for a human, but ideal work for a drone.
The research team designed a smartphone app that uses high-resolution video and artificial intelligence to identify potential larval sites, and it integrates that information with satellite data to produce a detailed map in real time. The smartphone app was first trained on known larval sites for Anopheles mosquitoes. The algorithm works by identifying the unique “fingerprint” of larval sites, which depends on characteristics such as whether the water is turbid or clean, stagnant or running, sunlit or shaded. This was done by determining the spectral “signature” of larval sites based on how it reflects or emits light of different wavelengths — including red, green, blue, near infrared and mid-infrared. Once the app has been trained on known larval sites, the drone can be flown at a higher altitude to survey a larger area and create a spatial map of where mosquitoes are likely to lay their eggs. The system can easily be adapted for different mosquito species that prefer to lay their eggs in different habitats.
Reducing the Burden of Infectious Diseases
The goal of the research team was to not only identify larval sites but also effectively treat the sites and reduce the burden of disease. The operation was dubbed Seek and Destroy. The test site was in the Gulu district of Northern Uganda, where 90% of the population engages in subsistence agriculture. Malaria infection occurs year-round, with peaks in June through July and September through October. Preventative measures include sleeping under insecticide-treated bed nets and regularly spraying indoor areas with insecticides. Members of the community who may be infected are tested for malaria and treated if any infection is detected. Treating malaria in the early stages reduces the possibility of serious complications.
In January 2021 — just before Seek and Destroy was initiated — 2,459 people in the community were tested for malaria, and 1,984 people tested positive and were treated. Larval sites were identified and treated in February and March, and weekly surveillance and treatment were conducted in April and May. By June, only 533 community members required testing for malaria, and just 2 people tested positive. June normally coincides with a peak in malaria infections. The number of adult female Anopheles mosquitos detected in 120 randomly selected homes was also reduced from hundreds to zero.
Different Species, Same Strategy
The strategy of killing eggs and larvae is the same regardless of the type of mosquito, where they live, or the disease they may carry. Other viral diseases transmitted by mosquitos include dengue fever, chikungunya fever, yellow fever, and Japanese encephalitis, as the World Health Organization explains.
It’s currently unclear whether this smartphone and drone approach can be effective against other disease-spreading insects. According to the University of Southern Florida newsroom, the technology used in Uganda is being adapted for black fly larvae, which can transmit a parasitic disease that causes blindness. However, what is clear is that innovative engineering and clever problem solving is spurring leaps forward in how we tackle worldwide medical problems.
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