Arguments in favour of a request for essential use of temephos for the treatment of nuisance and vector mosquito breeding sites
Context: nuisance and vectors mosquitoes are linked
Public operators in charge of the mosquito control in metropolitan France and French overseas Departments and Territories have mainly the mission to control nuisance and/or vector mosquitoes. The socio-economical stakes of mosquito control in the areas controlled by these operators are of first importance.
In the metropolitan area, the controlled species are essentially noxious. The mosquito control contributes mainly to local development and improves the well-being and health of inhabitants.
But this mosquito control is of public health concern in the French overseas Departments and Territories where mosquitoes transmit vectorial diseases such as dengue or malaria. Nevertheless, a vectorial risk, even low for the time being, do exists in metropolitan France (West Nile virus outbreaks in 1962, 1967, 2000 and 2003 et human cases en 2003, in southern France).
Moreover, the management of introduced tropical species, as potential arboviral disease vectors must be not neglected (i.e. Aedes albopictus, discovered in metropolitan France in 2000, now present in some cities of the Mediterranean coast has to be vigorously controlled because of its vectorial but also noxious capacities).
Temephos: essential for nuisance and vector mosquito control
Gathered by convention into a national agency (ADEGE)[1], French public mosquito control operators have been acting from several years for a global strategy in accordance with the politics of the European Commission, aiming in particular to reduce any environmental risk linked with pesticide use.
Further to the announcement of the non-notification of temephos by the main producer/manufacturer, the ADEGE has asked the French Ministry of Ecology and Sustainable Development apply for an essential use for temephos arguing that this organophosphorous larvicide is, up to now, one of the key elements in the control mosquito strategy, especially in the Mediterranean basin.
The ADEGE want to inform formally the European Commission that the quick withdrawal, in September 2006, of the use of temephos for controlling nuisance mosquitoes endangers the effectiveness of the larvicidal control, particularly in the Mediterranean area, in parts of the Atlantic coast and in the French overseas Departments and Territories
The alternative larvicides available on the market, i.e. Bacillus thuringiensis ser. israelensis (Bti) and some insect growth inhibitors (IGRs), such as diflubenzuron, to the need of effectiveness.
Bti acts by ingestion (and not by contact as temephos). Factors against the effectiveness of Bti are water temperatures lower than 10 to 12°C, low water depth, late instar larvae (ineffective against 4th instar larvae and pupae), mixtures of different larval instar resulting of a progressive flooding. If 100% effectiveness is not the aim, a loss of 10 to 15 % effectiveness on an area of several tenth or hundredth hectares will result in the production of millions of mosquitoes, which is unacceptable in most circumstances.
It should be noted that the Grande Camargue is not controlled up to now, even if an experimental trial will be undergoing in late 2006 and 2007. Adult mosquitoes from this area can fly up to Marseilles in the East and Montpellier in the West. These swarms of mosquitoes must be stopped by anti-adult treatments.
This situation confirms the need for considering adulticiding as an intrinsic part of the strategy. So we need finding alternative insecticides duly authorised for adult mosquito control in wetlands.
The paradox of the «all Bti»strategy is that it often involves the additional use of adulticides more aggressive than temephos which is used before the emergence of adults in well delimited areas.
In urban areas, the control of Culex pipiens is achieved with Bti and temephos, the only insecticides for which there is no resistance today.
Recall of arguments
- The antivectorial and nuisance control must not be separated, regarding the materials and methods used, even if methodologies and stakes differ.
In metropolitan France and French overseas departments and territories, we can find same species of mosquitoes that can be both pests and vectors.
dengue, present overseas, can be transmitted by Aedes albopictus, found in Metropolitan France in 2000 (Atlantic and Mediterranean coasts)
West-Nile virus, for which outbreaks along the Mediterranean coast is transmitted by Culex mosquitoes found everywhere in France.
Rift Valley fever now present in North Africa can be transmitted by several species of mosquitoes present in France andit is well known that the Mediterranean is not an effective barrier.
- The ADEGE declaration adopted in Fort-de-France (Martinique) in 2000, stated that a panel of active substances (Bti, temephos, fenitrothion, pyrethroids, and others) is essential for managing the resistance phenomenon (Culex, Aedes) and answering to the specific requirements of our missions. This declaration was published in the WHO bulletins to all Member States.
- The quick withdrawal of temephos might induce medical and sanitaryhazards, much more important than transient environmental impacts. The same phenomenon has be noted with the withdrawal of DDT from the list of substances used in public health and agriculture. WHO revised this decision, considering as a drawback in terms of public health.
- ADEGE is fully concerned by all the measures to protected environment. ADEGE is very active in its cooperation with bioinsectide manufacturers to evaluate new molecules or formulations, but these researches are time consuming and it is the reason why ADEGE asks for essential use of temephos. These researches have two objectives:
- the improvment of bioinsecticide formulations, in order to increase their effectiveness, and
- the finding of at least one alternative (larviciding and adulticiding) to temephos, taking into account environmentalprotection.
- In the list of 112 biocides substances notified in the 98/8/EC Directive for the product type n°18, very few might be usable for mosquito control and only a small number of manufacturers wish to fight for a specific use against mosquitoes. Beside Bti, there is diflubenzuron, an insect growth regulator but its environmental side effects must be fully studied and its mode of action implies, as does Bti, the absolute need of …an adulticide.
- Right now, there is no active substance available because they must firstly prove their cost-effectiveness in agriculture before the manufacturer’s engagement in the field of public health. The only notified exception is today the spinosad which belongs to a new family of bioinsecticides. It is studied at the present time by WHO (Whopes) as a potential larvicide. Its effectiveness and safety in the field have still to be proven. If it proves to be interesting, at least three years will be necessary for its registration in France. The mosquito control operators need time to get used to a new product especially as the concerned program covers wide territories and the economic and sanitary stakes are important.
- The availability of temephos must be permanent. The Art. 15th of the directive biocides offers the possibility to ask for essential use every time it is necessary for a maximum period of 120 days, in case of epidemics. But it can not answer to our specific needs in proper time due to the delivery delays from manufactures in foreign countries.Creation of strategic stocks is no realistic (2 year validity, non registered product). Finally this is unacceptable regarding the rules of the public market.
- The overcost of an “all Bti” program along the French Mediterranean coast is not conceivable in a such short delay, especially as it is less effective. It also involves additional costs for aerial means (the number planes must be doubled), the purchase of a minimum of 75,000 to 90,000 litres of formulated product, and of adulticides in case of failure!
- The impact of an«all Bti» program on the local economy of Languedoc-Roussillon might induce a deep crisis
- The problem of exotic mosquito species control, such as Aedes albopictus, and insect vectors of emerging diseases implies a rapid access to products other than Bti (including persistence of action, efficiency, resistance risk management), able to control mosquito larva and adults in out of reach breeding sites (i.e. used tires piles)
All this is a good arguments for the essential use of temephos by the French public operators of the ADEGE, for controlling mosquitoes whether there are pests or vectors.
This position is sustained unanimously by allelective peoples and administrations financing mosquito control programs in France.
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[1]ADEGE: «agence nationale pour la démoustication et la gestion des espaces naturels démoustiqués», founded by the convention of July 4th, 1996. It gathers the 3 EIDs (Méditerranée, Atlantique, Rhône-Alpes, including altogether 15 Departements), as well as the General councils of Martinique and French Guyana, and the SIVU of Lauterbourg (Alsace).