Mosquitoes in the spotlight: innovative techniques for mosquito control in Latin America

In Latin America, mosquito-borne diseases such as malaria, dengue and Zika represent a significant threat to public health. According to the Pan American Health Organization (PAHO), in 2022, 2,803,906 cases of dengue will be reported in the Americas, with more than 1,773 deaths (PAHO, 2023). With the growing global impact of vector-borne diseases, it is essential to implement effective control strategies to protect public health. Therefore, it is necessary to know the latest tools developed for mosquito control, analyzing the benefits and challenges that each one presents. Integrated mosquito management focuses primarily on controlling larvae or adults. Larvicides are deposited directly in aquatic areas where larvae can filter or come into contact with the product, while adulticides are used to control mosquitoes in flight or resting on previously sprayed surfaces. This means that both applications require a precise and strategic approach to their application. However, in both cases it is important to take into account the ecology, biology and behavior of the vector, for example: Where the breeding sites are, the most active hours of the adults and the preferred resting places of the species to be controlled. Mosquito larval control has had a constant evolution in recent decades, from the introduction of temephos in the 1950s to the applications of liquid and granular larvicides, such as spinosad or BTI, with aerial and terrestrial dissipation techniques. Thus, for control to be successful, it is crucial to use the appropriate larvicide for the mosquito species in question. In addition, areas where mosquito larvae develop must be identified and the larvicide applied in a precise and timely manner. One of the larvicide dispersal techniques currently used in urban mosquito control is Wide Area Larviciding (WAL) spraying. This consists of the application of liquid larvicides (mainly Spinosad and BTI) using a vertical atomizer with a range of up to 20 meters. The atomizer forms droplets of different sizes (< 50 to more than 600 microns), which when they reach their terminal height, disperse in areas to reduce the population of mosquito larvae. Larger droplets allow controlling larvae close to the street, such as in drains and pools of water, while smaller droplets can penetrate patios and areas behind houses to control cryptic or difficult-to-access breeding sites. For the application of WAL, various high-capacity equipment can be used, but the most recognized to date is the Buffalo Turbine, which uses a turbine to create an air current that disperses larvicide droplets over a wide radius. This airstream has a speed of up to 160 km/h and a Micronair nozzle (commonly used for aerial applications) AU5000 that rotates from 6,000 to 9,000 RPM. The nozzle sleeve can be redirected from the remote control to allow application in areas where environmental conditions do not favor cloud dispersion. Adulticides can be applied manually, terrestrially or aerially. Aerial applications are a rapid, extensive and highly effective method for controlling adult mosquitoes. Application should be done at specific times, during dusk or night hours, when mosquitoes are most active. Indoor residual spraying (IRS) is a widely used manual application method, which includes applying insecticides to walls and, in some cases, ceilings inside homes. This technique aims to get mosquitoes to land on sprayed surfaces. The insecticides used in the IRS have a residual effect that provides long-term protection against populations susceptible to the active ingredient of the formulation. However, the development of insecticide resistance has become a significant challenge to the effectiveness of IRS. Additionally, the IRS is labor intensive and may not be suitable for all housing types or areas with high mosquito density. One of the recent modifications to the IRS method includes the area-specific application approach known as Targeted Indoor Residual Spray (TIRS). Unlike the traditional IRS method, TIRS involves applying insecticides to specific indoor surfaces that are most likely to come into contact with larger numbers of mosquitoes. This technique is primarily aimed at urban areas and depends on community participation for its success. The TIRS methodology is more sustainable in terms of resources and reduces insecticide exposure of people living in the homes, compared to traditional IRS. Currently, the Autonomous University of Yucatán, in collaboration with Emory University (Prokopec Laboratory) and the Collaborative Unit for Entomological Bioassays (UCBE), leads the research and application efforts of TIRS worldwide. One of the most common and effective techniques for spatial mosquito control is thermofogging, an application that can be manual, terrestrial or aerial. Thermofogging includes the application of the product in the form of thermal mist. Insecticides are vaporized by heat, forming a fine mist that disperses in the air, affecting mosquitoes that come into contact with it. This technique is commonly used in urban areas to control intra- and peri-home populations of adult mosquitoes. Like the thermofogging technique, the Ultra Low Volume (UBV) application, also known as ULV (Ultra Low Volume) in English, involves the spatial dispersion of insecticides using the air pressure in the equipment. For this technique, a special nozzle is used that produces very small droplets, generally between 10 and 30 microns in average diameter, creating a cloud that disperses in the air and expands in the desired direction. This technique is highly effective in controlling adult mosquitoes in large areas if applied aerially, or precisely if applied terrestrially, and its success depends largely on the environmental conditions at the time of application. Aerial application of adulticides is highly effective in controlling adult mosquitoes, and for this, drones have proven to be a valuable tool for vector control, especially in difficult-to-access areas. The drones have been equipped with sprayers for the application of insecticides and larvicides, although their carrying capacity is limited. Additionally, drones can be used for surveillance and monitoring of mosquito populations in remote areas, such as mangroves, swamps or coasts, which helps vector control teams direct their efforts more effectively. The evolution of drone technology represents an increasingly important tool, especially with drones that have greater payload capacity and longer range flights. It is important to note that aerial or drone application can be costly and require significant resources in vector control programs. In addition to the techniques and equipment that use insecticides as the main control method, methods have been developed to reduce the transmission of vector diseases. For example, the release of Wolbachia-infected mosquitoes to suppress or replace populations or the release of genetically modified mosquitoes or sterile males resulting in a reduction in the vector population. These techniques rely on the biology of the vectors for their successful operation. Despite the many options and methods for mosquito control, in many cases, resources are limited, and it is important to find a balance and sustainable options. In these situations, vector control approaches that focus on prevention, such as eliminating mosquito breeding sites, and educating the community on how to prevent the reproduction of these insects, may be more effective. Integrated management is a joint effort that requires the collaboration of the community, private industry, government, and public health experts. We need every voice and resource to be maximized to combat the presence of mosquitoes in our populations. As new tools for their control are developed, it is important that these are accessible and effective for everyone, especially groups that are most vulnerable to vector-borne diseases. Finally, let us remember that mosquitoes do not distinguish borders and that we must work together, learn from the experiences of others and actively support research efforts, innovation and development of control techniques to ensure a healthier and safer future for populations. Product prequalified by the WHO An effective alternative for the control of adult populations of Aedes aegypti resistant to pyrethroids and organophosphates.