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The past 40 years have seen a dramatic emergence of epidemic arboviral diseases transmitted primarily by mosquitoes. The frequency and magnitude of the epidemics, especially those transmitted by urbanAedesspecies, have progressively increased over time, accelerating in the past 10 years. To reduce the burden and threat of vector-borne diseases, the World Health Organization (WHO) has recently adopted the Global Vector Control Response (GVCR) in order to support countries in implementing effective sustainable vector control. The evidence-base to support vector control is however limited for arboviral diseases which make prioritization difficult. Knowledge gaps in the distribution, mechanisms and impact of insecticide resistance on vector control impedes the implementation of locally tailoredAedescontrol measures. This report summarizes the main outputs of the second international conference of the Worldwide Insecticide resistance Network (WIN) on “Integrated approaches and innovative tools for combating insecticide resistance in arbovirus vectors” held in Singapore, 1–3 October 2018. The aims of the conference were to review progress and achievements made in insecticide resistance surveillance worldwide, and to discuss the potential of integrated vector management and innovative technologies for efficiently controlling arboviral diseases. The conference brought together 150 participants from 26 countries.

Only pyrethroid insecticides have so far been recommended for the treatment of mosquito nets for malaria control. Increasing resistance of malaria vectors to pyrethroids threatens to reduce the potency of this important method of vector control. Among the strategies proposed for resistance management is to use a pyrethroid and a non-pyrethroid insecticide in combination on the same mosquito net, either separately or as a mixture. Mixtures are particularly promising if there is potentiation between the two insecticides as this would make it possible to lower the dosage of each, as has been demonstrated under laboratory conditions for a mixture of bifenthrin (pyrethroid) and carbosulfan (carbamate). The effect of these types of treatment were compared in experimental huts on wild populations of Anopheles gambiae Giles and the nuisance mosquito Culex quinquefasciatus Say, both of which are multi-resistant. Four treatments were evaluated in experimental huts over six months: the recommended dosage of 50 mg m−2 bifenthrin, 300 mg m−2 carbosulfan, a mosaic of 300 mg m−2 carbosulfan on the ceiling and 50 mg m−2 bifenthrin on the sides, and a mixture of 6.25 mg m−2 carbosulfan and 25 mg m−2 bifenthrin. The mixture and mosaic treatments did not differ significantly in effectiveness from carbosulfan and bifenthrin alone against anophelines in terms of deterrency, induced exophily, blood feeding inhibition and overall mortality, but were more effective than in earlier tests with deltamethrin. These results are considered encouraging, as the combination of different classes of insecticides might be a potential tool for resistance management. The mixture might have an advantage in terms of lower cost and toxicity

International audience; Extraits du Rapport du groupe de travail du 9 novembre 2012, présidé par Éric Caumes, de la Commission spécialisée des maladies transmissibles du Haut Conseil de la santé publique (HCSP).

En Côte-d'Ivoire, le développement de la culture de riz dans les bas-fonds n'a pas d'effet ni sur l'infection ni sur la maladie palustre, en zone de savane comme en zone de forêt. Le parasite Plasmodium falciparum a été trouvé très résistant au traitement par la chloroquine en zone forestière alors qu'il y était sensible en zone de savane. Inversement, le vecteur Anopheles gambiae s.l. a été trouvé résistant aux insecticides pyréthrinoïdes en zone de savane alors qu'il y était sensible en zone forestière. Cette résistance est liée à une mutation du gène kdr. La mise en place au niveau national des combinaisons thérapeutiques à base d'artémisinine a permis de résoudre le problème de la résistance des parasites à la chloroquine. Par ailleurs, il a été démontré que les moustiquaires imprégnées de pyréthrinoïdes utilisées dans la lutte antivectorielle ont conservé leur efficacité contre la morbidité de la malaria dans les zones où An. gambiae s.l. a été trouvé résistant à ces insecticides.

L'efficacité d'un hamac expérimental muni d'une couverture en moustiquaire, tous deux en polyéthylène imprégné d'un insecticide pyréthrinoïde (perméthrine) et à longue durée d'efficacité, a été testée dans une case expérimentale en parpaings de ciment contre des populations naturelles de Anopheles gambiae s.l., vecteur de paludisme, et de Mansonia africana (Theobald) et Mansonia uniformis (Theobald), moustiques nuisants et vecteur d'arboviroses. Le hamac a été évalué pendant 20 semaines consécutives en comparaison avec des tortillons insecticides. 2,227 moustiques (130 An. gambiae et 2,097 Mansonia spp.), soit 27,8 moustiques par nuit de capture ont été collectés dans la case non traitée (témoin). L'effet répulsif des tortillons comme celui du hamac ont diminué significativement le taux d'entrée des moustiques dans les cases (de 35 à 60%). Le pourcentage d'inhibition du taux de piqûres a été élevé, tant pour les tortillons que le hamac (de 93 à 97%) ainsi que la mortalité (de 88 à 98%). En protégeant durablement les personnes dormant à l'intérieur des habitations, il apparaît que les hamacs imprégnés sont plus pratiques que les tortillons dans la mesure où ces derniers doivent être remplacés chaque nuit. Il serait intéressant d'évaluer l'efficacité de ces hamacs imprégnés contre les vecteurs exophages dans la mesure où la plupart des gens dormant spontanément dans des hamacs les utilisent à l'extérieur.

The kdr mutation, conferring resistance to pyrethroid insecticides, has been reported in several West-African populations of Anopheles gambiae S form and in the M form populations from tropical forest of Benin. We report the finding of a single M specimen collected in the rice-field area of Vallée du Kou (Burkina Faso) showing the mutation at the heterozygous state. The monitoring of kdr mutation in An. gambiae forms/species is of paramount importance to implement effective malaria control tools and may greatly improve the knowledge of the relationship between and within An. gambiae populations.

The effects of impregnated bednets treated with deltamethrin at a dosage of 25 mg a.i./m2 were evaluated at two testing stations in Côte d'Ivoire. The first one was located in Yaokoffikro, where Anopheles gambiae s.s. are resistant to pyrethroids (including deltamethrin), and the second in M'be, close to a large rice-growing area where An. gambiae s.s. are susceptible pyrethroids. In both situations, treating bednets with deltamethrin was very effective in limiting contact between man and vector. 72% fewer female An. gambiae entered the huts in the susceptible area, whereas a decrease of 43% was recorded in the resistant area, indicating that deltamethrin still has a certain repellent effect on resistant populations of An. gambiae s.s. Overall mortality induced by bednets treated with insecticide was significantly higher in the resistant area (56.4% as versus 44.3%). An explanation for this apparent paradox is that the mosquitoes being less repelled by the insecticide remain on the treated material for longer periods of time and most of them eventually die. The results of this study indicate that bednets treated with deltamethrin are an effective prophylactic measure even in areas where An. gambiae s.s. are resistant to pyrethroids and should still be considered as a practical means of personal protection against malaria even in pyrethroid resistance areas with high frequency of kdr resistance genes.

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