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      The combination of NPK fertilizer and deltamethrin insecticide favors the proliferation of pyrethroid-resistant Anopheles gambiae (Diptera: Culicidae) Translated title: L’association de l’engrais NPK et de l’insecticide deltaméthrine favorise la prolifération d’ Anopheles gambiae (Diptera: Culicidae) resistants aux pyréthrinoïdes

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          Abstract

          In this laboratory study, we investigated how the biological cycle of Anopheles gambiae s.s. (VKPR strain) would be like when grew in an environment containing more or less plant matter (2.5 or 5 g/l) and fertilizer (8-12-8 or 17-23-17 mg/l). Half of the environments studied were not exposed to insecticide (control) whereas the other half was submitted to deltamethrin treatment at the concentration of 0.015 mg/l. The bioassays showed that 2.5 g/l of plant matter in water are not sufficient to feed the hundred larvae, each breeding site contains. Treating these breeding sites with deltamethrin reversed the situation as it decreased the competition for food resources and allowed the surviving larvae to share the small amount of food enabling them to pursue their development until adults. If the introduction of NPK in untreated sites has not improved the nutritive qualities of the water, in the treated sites it multiplied the number of emerging adults by 2.5. In the waters containing 5 g/l of plant matter, the larvae did not undergo feeding competition and the impact of insecticide followed of a more traditional selection scheme that expressed itself by a lower number of emerging adults. In these environments treated or nontreated where plant matter is abundant, adding NPK brings food supplement to the larvae therefore increases the survival rate of An. gambiae. To conclude, whether in habitats with little or much plant matter, NPK presence in water results in larger adults with generally, more soluble proteins.

          Translated abstract

          Dans cette étude de laboratoire, les auteurs ont étudié le cycle biologique d ’Anopheles gambiae s.s. résistant aux pyréthrinoïdes (souche VKPR) selon que celui-ci se développe dans un environnement plus ou moins riche en matière végétale (MV = 2,5 et 5 g/l) et en engrais NPK (8-12-8 et 17-23-17 mg/l). La moitié des environnements composés n’a subi aucune pression de sélection (gîtes témoins) alors que l’autre moitié a fait l’objet d’un traitement à la deltaméthrine à la concentration de 0,015 mg/l. Les essais ont montré que 2,5 g de MV par litre d’eau ne suffisent pas à nourrir la centaine de larves contenue dans chaque gîte. Le fait de traiter ces gîtes avec la deltaméthrine inverse toutefois la situation en donnant aux larves survivantes l’occasion de se partager le peu de nourriture disponible et de poursuivre ainsi leur développement jusqu’au stade adulte. Si l’apport en NPK dans les gîtes non traités n’a pas amélioré les qualités nutritives des eaux, cet apport dans les gîtes traités a multiplié par 2,5 le nombre des adultes émergents. Dans les eaux contenant 5 g de MV par litre, les larves n’ont pas subi de stress alimentaire et l’impact de l’insecticide a suivi un schéma de sélection plus classique qui s’est exprimé par une réduction du nombre des adultes émergents. Dans ces environnements (traités ou non) où abonde la matière organique, l’ajout de NPK apporte aux larves un complément nutritionnel qui augmente plus encore le taux de survie d ’An. gambiae. Enfin, que ce soit dans les milieux pauvres ou riches en MV, la présence de NPK dans l’eau engendre des adultes plus gros et généralement plus riches en protéines solubles.

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          Most cited references 10

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          Pyrethroid resistance in African anopheline mosquitoes: what are the implications for malaria control?

          The use of pyrethroid insecticides in malaria vector control has increased dramatically in the past decade through the scale up of insecticide treated net distribution programmes and indoor residual spraying campaigns. Inevitably, the major malaria vectors have developed resistance to these insecticides and the resistance alleles are spreading at an exceptionally rapid rate throughout Africa. Although substantial progress has been made on understanding the causes of pyrethroid resistance, remarkably few studies have focused on the epidemiological impact of resistance on current malaria control activities. As we move into the malaria eradication era, it is vital that the implications of insecticide resistance are understood and strategies to mitigate these effects are implemented. Copyright © 2010 Elsevier Ltd. All rights reserved.
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            The role of agricultural use of insecticides in resistance to pyrethroids in Anopheles gambiae s.l. in Burkina Faso.

            Agricultural use of insecticides is involved in the selection of resistance to these compounds in field populations of mosquitoes in Burkina Faso. Anopheles gambiae s.l. was resistant to permethrin and DDT in cotton-growing and urban areas, but susceptible in areas with limited insecticide selection pressure (rice fields and control areas). Nevertheless, resistance to these insecticides was observed in a village on the outskirts of the rice fields at the end of the rainy season, suggesting that the latter population of mosquitoes had migrated from the surrounding cotton villages into the rice fields. A seasonal variation of resistance observed in the cotton-growing area is related to the distribution of the molecular M and S forms of An. gambiae, since resistance to pyrethroids has so far only been reported in the S form. Pyrethroid resistance in west African An. gambiae was conferred by target site insensitivity through a knockdown resistance (kdr)-like mutation, which was present at high frequencies in mosquitoes in the cotton-growing and urban areas.
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              Cotton pest management practices and the selection of pyrethroid resistance in Anopheles gambiae population in Northern Benin

              Background Pyrethroid insecticides, carbamate and organophosphate are the classes of insecticides commonly used in agriculture for crop protection in Benin. Pyrethroids remain the only class of insecticides recommended by the WHO for impregnation of bed nets. Unfortunately, the high level of pyrethroid resistance in Anopheles gambiae s.l., threatens to undermine the success of pyrethroid treated nets. This study focuses on the investigation of agricultural practices in cotton growing areas, and their direct impact on larval populations of An. gambiae in surrounding breeding sites. Methods The protocol was based on the collection of agro-sociological data where farmers were subjected to semi-structured questionnaires based on the strategies used for crop protection. This was complemented by bioassay tests to assess the susceptibility of malaria vectors to various insecticides. Molecular analysis was performed to characterize the resistance genes and the molecular forms of An. gambiae. Insecticide residues in soil samples from breeding sites were investigated to determine major factors that can inhibit the normal growth of mosquito larvae by exposing susceptible and resistant laboratory strains. Results There is a common use by local farmers of mineral fertilizer NPK at 200 kg/ha and urea at 50 kg/hectare following insecticide treatments in both the Calendar Control Program (CCP) and the Targeted Intermittent Control Program (TICP). By contrast, no chemicals are involved in Biological Program (BP) where farmers use organic and natural fertilizers which include animal excreta. Susceptibility test results confirmed a high resistance to DDT. Mean mortality of An. gambiae collected from the farms practicing CCP, TICP and BP methods were 33%, 42% and 65% respectively. An. gambiae populations from areas using the CCP and TICP programs showed resistance to permethrin with mortality of 50% and 58% respectively. By contrast, bioassay test results of An. gambiae from BP areas gave a high level of susceptibility to permethrin with an average mortality of 94%. Molecular analysis identified An. gambiae s.s, and An. arabiensis with a high predominance of An. gambiae s.s (90%). The two molecular forms, M and S, were also determined with a high frequency of the S form (96%). The Kdr gene seemed the main target- site resistance mechanism detected in CCP, TICP, and BP areas at the rates ranging from 32 to 78%. The frequency of ace-1R gene was very low (< 0.1). The presence of inhibiting factors in soil samples under insecticide treatments were found and affected negatively in delaying the development of An. gambiae larval populations. Conclusions This research shows that Kdr has spread widely in An. gambiae, mainly in CCP and TICP areas where pyrethroids are extensively used. To reduce the negative impact of pesticides use in cotton crop protection, the application of BP-like programs, which do not appear to select for vector resistance would be useful. These results could serve as scientific evidence of the spread of resistance due to a massive agricultural use of insecticides and contribute to the management of pesticides usage on cotton crops hence reducing the selection pressure of insecticides on An. gambiae populations.
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                Author and article information

                Journal
                Parasite
                Parasite
                parasite
                Parasite : journal de la Société Française de Parasitologie
                EDP Sciences
                1252-607X
                1776-1042
                May 2012
                15 May 2012
                : 19
                : 2 ( publisher-idID: parasite/2012/02 )
                : 159-164
                Affiliations
                [1 ] Institut de Recherche pour le Développement (IRD), Unité Mixte de Recherche (UMR) Maladies Infectieuses et Vecteurs, Écologie, Génétique, Évolution et Contrôle (MIVEGEC), Laboratoire de Lutte contre les Insectes Nuisibles (LIN) 911, avenue Agropolis BP 64501 34394 Montpellier Cedex 5 France
                Author notes
                [* ]Correspondence: Frédéric Darriet. Tel.: 33 (0)4 67 04 19 24 – Fax: 33 (0)4 67 54 20 44. E-mail: frederic.darriet@ 123456ird.fr
                Article
                parasite2012192p159 10.1051/parasite/2012192159
                10.1051/parasite/2012192159
                3671440
                22550627
                © PRINCEPS Editions, Paris, 2012

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                Figures: 3, Tables: 2, Equations: 0, References: 26, Pages: 6
                Categories
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