Malaria, dengue fever, chikungunya or Zika virus fever, with climate change and globalization, diseases caused by infectious agents transmitted by arthropods, in particular mosquitoes, have been reappearing for several years. The tiger mosquito, vector of several viruses, arrived in Metropolitan France in 2004 and imported or native cases of dengue fever, chikungunya and Zika are regularly detected there. In this context and in the absence of vaccine and specific treatment once morest these diseases, the fight once morest mosquitoes transmitting the viruses responsible for these diseases remains the main means of action. This fight involves the implementation of different strategies combining chemical and non-chemical means.
Insecticides, a solution with limits
Repeated use of the same insecticidal substance gives a selective advantage to resistant mosquitoes which can proliferate. Various active substances formerly used have been deemed dangerous for humans or the environment and have been gradually withdrawn from the market. Today, in France, very few active substances are used in vector control. Treatments essentially focus on an active substance targeting mosquito larvae, Bti, and another targeting adult mosquitoes, deltamethrin. However, the massive use of deltamethrin, without alternating with other active substances, has led to the appearance of resistance in mosquitoes in the overseas departments. Other substances and means of control are therefore to be developed.
ANSES involved in the identification of new substances once morest vectors
The use in France of biocidal products, including insecticides, is governed by European regulations. ANSES is responsible for assessing biocidal products according to these regulations and issuing marketing authorisations. In order to identify potential alternatives that would lead to the diversification of products that can be used in vector control, ANSES has for several years undertaken an inventory of active substances with reported or supposed activity on mosquitoes and their families, as well as on biting insects. (flies, horseflies). A total of 129 substances were thus identified. These molecules were then compared according to toxicity, ecotoxicity and environmental contamination criteria. In 2012, this analysis led to the selection of 32 active substances (PDF), potentially usable once morest adult mosquitoes or larvae, and on which the Agency recommended that research and development efforts focus more particularly. In 2016, this inventory was updated (PDF) in the light of the European regulatory framework and their possible use in the medium term in France. The Agency has also produced several opinions and reports on the use of impregnated mosquito nets during the chikungunya epidemics in 2006 and Zika virus fever in 2016.
Non-chemical methods, to be used as first intention
To avoid the emergence of resistance and limit the impact of products on humans and the environment, non-chemical methods should be preferred whenever possible. Treatments using adulticidal insecticides must remain specific means, intended to prevent the spread of the disease around sources of contamination within a well-defined framework, depending in particular on the epidemiological context and local conditions. ANSES recommends that they be used as part of an integrated pest management strategy, combining several approaches, including:
- social mobilization and public education, in order to promote good practices in the fight once morest mosquitoes and vector-borne diseases. The objective is to induce a lasting change in behavior, to maintain preventive measures once morest mosquito bites, such as mechanical control;
- mechanical control: it can target the larvae, by eliminating stagnant water, in which mosquitoes can lay their eggs, such as in flower pots, containers or used tires. Mechanical control can also target adult mosquitoes, with the setting of traps;
- prevention once morest mosquito bites, which essentially involves individual protection. It is therefore recommended, first of all, to wear loose and covering clothes and to sleep under mosquito nets. If these non-chemical measures are insufficient, it is advisable to apply suitable repellent products to the skin or clothing, favoring products with marketing authorization, and following the instructions for use, as well as than to resort to the use of mosquito nets impregnated with insecticide.
Other innovative methods are studied. ANSES has funded studies on alternatives to insecticides. In particular, the use of bacteria or viruses which kill mosquitoes is envisaged. Attempts to release male mosquitoes which cannot produce offspring, either because they have been made sterile or because they carry bacteria which make them incompatible with females, are also implemented.