Could mosquito traps provide an additional tool for controlling vector-borne diseases?
Mosquito traps are increasingly used in public spaces as a means to prevent mosquito bites and to control mosquito-borne diseases. However, the studies currently available are not sufficient to demonstrate the short-term effectiveness of these traps in preventing the spread of mosquito-borne diseases. ANSES is therefore encouraging their use primarily as a preventive measure (in the medium and long term) to reduce high mosquito density as part of an integrated control strategy. ANSES also points out that the marketing and use of these traps must comply with regulations.
In recent decades, a number of mosquito-borne diseases – such as dengue, chikungunya and Zika – have spread outside tropical regions. The use of mosquito traps as a complement or alternative to other techniques for controlling the spread of viruses, is a relatively recent idea. In France, the operators responsible for limiting the spread of mosquitoes are appointed by the Regional Health Agencies (ARSs). Some 15 operators currently exist, but they do not all use mosquito traps in the same way. ANSES conducted a literature review to assess the effectiveness of the mosquito traps used by operators as part of vector control.
Several ways to attract female mosquitoes
Two main types of trap are used to catch female mosquitoes, which are the only ones able to bite and to transmit pathogens. The first type of trap simulates an egg-laying site. A water-filled container uses a variety of means, including insecticide and glue strips, to trap the females when they come to lay their eggs. The second type of trap attracts mosquitoes by simulating the breathing of a living being through the diffusion of carbon dioxide (CO2) and/or the use of visual or olfactory attractants (for example, lactic acid to simulate human body odour).
A control method to be used alongside other techniques
“We have a body of evidence showing that both types of trap can have a preventive effect in reducing the mosquito population in the medium and long term (over several weeks, months, or even years), providing that they are well maintained and used in sufficient numbers,” says Johanna Fite, head of the "Vectors" unit at ANSES. “However, they are not a magic solution. Traps are most effective when used in conjunction with other control methods, particularly the elimination of breeding sites."
No studies concerning the impact of traps on the spread of disease
Some operators place traps when cases of vector-borne disease are identified. Traps are set up for a period of three to six weeks around the homes of infected people. The expert appraisal conducted by ANSES identified no data shedding light on the effectiveness of traps in quickly containing the spreading of disease when the viruses are already in circulation. The Agency therefore recommends that research be carried out in order to collect data on this question and to determine the best conditions for the deployment of these traps, based on different epidemiological scenarios, including an isolated case, an outbreak and an epidemic. Pending these additional data, mosquito traps should be used only as a preventive measure, or in cases where it is not possible to use an insecticide, for example when the area to be treated is inaccessible or close to a waterway.
A reminder needed of the regulations
CO2, lactic acid and other substances used to attract female mosquitoes are biocidal substances. Traps using these substances must therefore comply with the regulations on biocides. They also require marketing authorisation (MA). To date, no applications for marketing authorisation have been filed in France for mosquito traps using CO2. Under the terms of a transitional regime, the marketing of traps using CO2 produced through combustion is authorised until July 2022. After this date, it will no longer be possible to sell traps without a marketing authorisation in France. Applications for marketing authorisation must include documentary proof of the effectiveness and safety of these traps. Finally, devices will not be able to make claims such as "zero nuisance" or "mosquito-free home" without proof.