A few years ago, some researchers had a crazy idea. What if we infected mosquitoes with their own pathogens and released them into the wild? That has since become one of our best weapons against mosquito populations. However, releasing them manually is time-consuming and inefficient. So instead, researchers have come up with a new plan: drones.

A small, unassuming white box designed by researchers is capable of carrying up to 160,000 mosquitoes. The mosquitoes are divided into multiple compartments, to be released at different times (and in different places).

Mosquito attack

Over the past 50 years, the incidence of diseases such as dengue fever, chikungunya, and Zika has surged. Traditional methods of controlling mosquito populations, such as insecticide use, have proved insufficient and sometimes harmful. The World Mosquito Program (WMP) has developed an innovative approach to combat these diseases by introducing Wolbachia bacteria into native Aedes aegypti mosquito populations.

This approach, of fighting parasites with parasites, aims to reduce the transmission of these diseases without attempting to eradicate the mosquito species itself.

In a recent study, the WMP demonstrated a 77% reduction in dengue cases in Yogyakarta, Indonesia, using Wolbachia-infected mosquitoes. However, it’s hard (and sometimes dangerous) to transport these infected mosquitoes.

So instead, researchers have developed an automated mosquito dosing and release system integrated into uncrewed aerial vehicles (UAVs). This new method aims to facilitate large-scale mosquito releases with less labor and risk.

Bacteria, fight these mosquitoes for me

Aedes aegypti mosquitoes are primary vectors for several debilitating diseases — and their spread is increasing. Because of globalization, urbanization, and climate change, these mosquitoes can thrive in larger and larger areas. Consequently, about 53% of the global population now lives in areas conducive to dengue transmission, resulting in 390 million cases annually and significant economic burdens on healthcare systems.

These mosquitoes are the prime target for such approaches.

There are several mosquito-release control strategies, such as the Sterile Insect Technique (SIT) and the Incompatible Insect Technique (IIT). Most involve releasing sterile or incompatible male mosquitoes to reduce mosquito populations. However, these techniques require continuous releases of large numbers of mosquitoes and are still not fully proven at large scales.

The Wolbachia method offers a promising alternative.

Wolbachia is a naturally occurring bacterium that, when introduced into Aedes aegypti populations, can prevent these mosquitoes from transmitting viruses like dengue, Zika, and chikungunya. The bacterium is maternally inherited, meaning it is passed from mother to offspring, and it also causes uninfected females to produce inviable eggs when they mate with infected males.

This new system is designed to release small batches of mosquitoes over wide areas, ensuring effective coverage without the need for extensive ground operations. Essentially, the UAV-mounted system releases 100-200 mosquitoes per shot. The drone flies over a pre-determined route, releasing the mosquitoes at key sites. During transport, it maintains optimal transport and humidity for the mosquitoes to ensure that they can survive and spread the bacteria.

Testing it out

The system was tested in Fiji. Before testing it, however, researchers sought approval from local communities in Fiji. Surveys conducted in revealed high levels of community awareness and acceptance of the Wolbachia method and UAV technology. Most residents felt positive or neutral about the use of UAVs to release Wolbachia-infected mosquitoes.

Over four weeks, paired aerial and ground releases of Wolbachia-infected mosquitoes were conducted. Despite some technical issues during the first aerial releases, the overall results showed similar mosquito recapture rates for both methods. The second trials involved improved UAV release mechanisms and longer release durations.

The UAV-based system successfully established Wolbachia infections in the local mosquito population, with Wolbachia prevalence remaining high one year after the final release.

Overall, the system proved its effectiveness and shows it can be an important tool in our fight against mosquito-borne diseases.

Journal References:

a-Hsun Lin et al, Field deployment of Wolbachia -infected Aedes aegypti using uncrewed aerial vehicle, Science Robotics (2024). DOI: 10.1126/scirobotics.adk7913

Jacob E. Crawford, Virus-blocking mosquitoes take flight in the fight against dengue, Science Robotics (2024). DOI: 10.1126/scirobotics.adr0224