This article is republished from The Conversation under a Creative Commons license. Read the original article.
With the return of fine weather, the nuisance associated with mosquitoes is a growing concern for many people and communities looking for effective means of control to protect themselves from the bites and diseases likely to be transmitted by these insects. Remember that in mainland France, the tiger mosquito (Aedes albopictus) is the only one capable of transmitting the viruses responsible for dengue fever, chikungunya and Zika. Arriving in mainland France in 2004 in the Alpes Maritimes, it moved north and colonized 67 departments.
Since decree of March 29, 2019, mayors have new responsibilities in terms of vectors, since it is now within their competence to “act to prevent the establishment and development of insect vectors in (their) municipality”. As such, they can in particular inform the population regarding the necessary preventive measures and set up actions to raise public awareness, or even a program to identify, treat and control public sites likely to facilitate the development of insect vectors.
In this context, some communities, such as Libourne or the municipality of Sambuc, in the Camarguehave decided to deploy electric “mosquito traps” or “mosquito terminals” placed outdoors in order to reduce the presence of mosquitoes and reduce the nuisance caused by bites.
However, these devices are expensive (a few hundred to more than €2,000 per unit), demanding in terms of maintenance (replacement of consumables: bottle of CO2olfactory lure, capture net, etc. and their effectiveness is relative.
The National Agency for Food, Environmental and Occupational Health Safety (ANSES) has published an opinion and an expert report on the effectiveness of traps used once morest mosquitoes Aedes arbovirus vectors in September 2021 to which we contributed.
It also issued recommendations for studies aimed at evaluating trapping methods in terms of cost-effectiveness and feasibility following a rigorous scientific evaluation protocol to be carried out.
Several types of traps exist
There are two main types of traps used to control female mosquitoes, which are the only ones to bite: lethal ovipositor traps targeting females looking for a place to lay their eggs and traps targeting unfed females looking for food. host (because they need a blood meal to bring their eggs to maturity).
The first, imitating a place of laying, consist of a container filled with stagnant water and make it possible to trap by various means (laying medium impregnated or treated with an insecticide or sticky strips inside the trap) the females seeking to lay. These traps aim to reduce the number of adult female mosquitoes and that of their future offspring (the larvae can also be killed in the trap by insecticide residues or using a mesh that prevents the emergence of adults) . However, if these traps are not maintained (regular water changes), they can themselves become breeding grounds for adult mosquitoes.
The second type of trap attracts female mosquitoes in search of a host by simulating the respiration of a living being by the diffusion of carbon dioxide (CO2) and/or using light and/or an olfactory lure (for example by simulating human body odor with lactic acid).
Mosquitoes drawn into the trap are then sucked up by electric ventilation and rushed into a capture net. Unlike so-called “passive” nest traps, these are called “active” because they need electricity to operate and use a lure.
Marketed traps must demonstrate their effectiveness
According to the data available in the scientific literature (which concern the BG GAT, CDC AGO, BG Sentinel, MosquiTRAP, and BioBelt Anti-Mosquitoes trap models), passive and active traps can contribute to significantly reducing mosquito populations in gender Aedes in the medium and long term (over several weeks, months or even years), provided that they are well maintained and that there are a sufficient number of traps in the area to be protected.
The effectiveness of other traps marketed in France to reduce the density of mosquitoes is not yet documented.
While waiting to have these data, the claims used by certain manufacturers, such as “zero nuisance” or “mosquito-free house” seem excessive. Such claims should not be made without proof of what they claim being established and only for products that otherwise fully meet the applicable regulatory requirements.
As part of our review of the scientific literature, no evidence was found regarding the effectiveness of mosquito traps in rapidly limiting the spread of vector-borne diseases when viruses are already in circulation. Virus transmission by mosquitoes is a multifactorial phenomenon, and mosquito density is only one of the factors that help explain the circulation of viruses among others (such as socio-economic, behavioral, environmental and case management).
While some traps may be effective in reducing mosquito populations, their effectiveness in reducing the spread of vector-borne diseases has not been demonstrated We therefore recommend conducting research to collect such data and determine the optimal deployment conditions for these traps . Pending this additional data, mosquito traps should only be used when it is not possible to use the insecticide treatments currently recommended around the cases, for example when the area to be treated is close to a watercourse. or inaccessible or, in addition to other preventive measures.
Some marketed traps are subject to marketing authorization
With CO2, lactic acid and other substances used to attract female mosquitoes are “biocidal” substances. The traps using them must therefore comply with the European regulation on biocides and benefit from a marketing authorization (AMM). Examination of the MA application dossier for a product makes it possible to assess the efficacy of the product, as well as the risks for humans and the environment.
To date, none of the mosquito traps using CO2 marketed in France does not have MA. The commercialization of CO traps2 produced by combustion of butane/propane is authorized under a transitional regime until 1is July 2022. After this date, traps without marketing authorization can no longer be marketed in France.
Traps should be used in addition to other preventive measures
Traps are not a silver bullet. To be more effective, they must be used in addition to other means of control, starting with the treatment of the problem at the source and the elimination of breeding sites. Indeed, the effective elimination of stagnant water deposits is the main means of combating the spread of mosquitoes. To do this, every gesture counts (emptying the cups under the flower pots, ensuring that the gutters run smoothly, collecting waste so that it does not turn into a receptacle for rainwater, etc.) and it is essential that each citizen involved in the fight once morest breeding sites.
To find out more regarding the measures that mayors can take in this area, there is a Guide for local authorities wishing to implement a fight once morest urban mosquito vectors of dengue, chikungunya and Zika published in 2016 by the National Center of Expertise on Vectors. Even if this guide is no longer up to date on regulatory issues, it is rich in advice and recommendations for carrying out integrated pest management combining biological, physical, chemical and social mobilization measures, with a dual objective of effectiveness in combating once morest the targeted mosquito population and respect for the environment.
Thierry BaldetSearcher, CIRAD
