The efficacy of a chitin synthesis inhibitor against field populations of organophosphate-resistant Aedes aegypti in Brazil

Abstract

Key words: Aedes aegypti -chitin synthesis inhibitors -temephos -deltamethrin -novaluron -cross-resistance Among the arboviruses transmitted by mosquitoes throughout the world, dengue is presently the most relevant; it is endemic to all of the continents, except Europe (Nogueira et al. 2001, Forattini 2002, Claro et al. 2004. Brazil has an alarming dengue incidence with several outbreaks all over the country and an increasing incidence of severe cases. Therefore, major public health campaigns target this disease (Teixeira et al. 1999, Câ-mara et al. 2007, MS/SVS 2009.Specific drugs and an effective vaccine against dengue virus are not yet available (Durbin & Whitehead 2010). Consequently, the only way to control the dengue epidemiological network is to target the virus' vector, Aedes aegypti (Medronho 2006. Although the elimination of potential Aedes breeding sites is increasingly considered a crucial component of dengue control, the utilisation of chemical insecticides is still a common measure. Until very recently, the most commonly used insecticides against Aedes in Brazil were the organophosphate temephos and the pyrethroid deltamethrin, which are used to control the larval and adult populations, respectively .The continuous use of chemical insecticides can lead to the dissemination of resistance and the consequent failure of the control efforts. Therefore, alternative methods of controlling disease-transmitting vectors are urgently needed. Two examples are entomopathogenic bacteria and insect growth regulators (IGRs). The biological insecticide Bacillus thuringiensis serovar israelensis (Bti) has been employed against Ae. aegypti in various municipalities of Brazil. However, the reduced field persistence of commercially available Bti formulations is an obstacle; under tropical conditions, the maximal residual effect observed lasted four weeks .In contrast to the classical chemical insecticides and biolarvicides, IGRs are not directly toxic, but act selectively on the development, metamorphosis or reproduction of the target insect species (Hoffmann & Lorenz 1998, Martins & Silva 2004. Among IGRs, the chitin synthesis inhibitors (CSIs) act by interfering with the synthesis or deposition of chitin on the exoskeleton or other chitinised internal structures, such as the peritrophic matrix (Merzendorf & Zimoch 2003, Merzendorf 2005.Novaluron is a CSI that is already utilised in agriculture. It is highly effective against Coleoptera, Homoptera and Lepidoptera larvae of several crop pests . It can act through ingestion, as verified in the larvae of the moth species Spodoptera littoralis and Helicoverpa armigera, or through contact, as reported with the flies Bemisia tabaci and Trialeurodes vaporariorum (Ishaaya et al. 1996(Ishaaya et al. , 1998. Novaluron is also efficient against Ae. aegypti larvae, as reported by Mulla et al. (2003) and Arredondo-jiménez and Valdez-Delgado (2006). Because novaluron is recommended by the World Health Organization for use in drinking water, it represents a potential tool in the con...

Toxicity of spinosad to temephos-resistant Aedes aegypti populations in Brazil

“…aegypti resistance to chemical products has been reported around the globe [50–56]. In Brazil, the detection of populations resistant to the temephos larvicide started in 1998 [14–16]. Because of this, additional to elimination or correct treatment of larvae breeding sites, there was a need to search for alternative compounds for Ae .…”

“…In Brazil, the control of dengue vector larvae has been carried out for decades with the use of temephos, an organophosphate larvicide. Resistance to this compound has been reported since 1998 [14–16]. Nowadays the majority of the evaluated Brazilian populations is resistant to temephos [14,17–20].…”

Temporal variation of wing geometry in Aedes albopictus

“…For instance, the evolutionary changes within a species may produce populations that are resistant to insecticides (Braga et al 2004, da-Cunha et al 2005, Gómez et al 2011, Fontoura et al 2012 or may alter their vectorial capacity (Almeida et al 2005, Freitas 2010). Although microevolution has been investigated in the congeneric dengue vector Aedes aegypti (Lourenço-de-Oliveira et al 2004, Costa-Ribeiro et al 2007, Vidal & Suesdek 2012, the knowledge of microevolution in Ae.…”

Triflumuron Effects on the Physiology and Reproduction ofRhodnius prolixusAdult Females

“…Interestingly, topical and impregnated surfaces treatments showed similar cumulative mortalities after 30 days. This indicates that, in spite of the stronger effect in the first day for the topical treatment, possibly due to better penetration, TFM impregnated surfaces are able to affect the insects during a more prolonged period, suggesting that, under our experimental conditions, environmental degradation of TFM is negligible [66]. …”