Resistance Status to the Insecticides Temephos, Deltamethrin, and Diflubenzuron in BrazilianAedes aegyptiPopulations

Abstract

Insecticides are still largely applied in public health to control disease vectors. In Brazil, organophosphates (OP) and pyrethroids (PY) are used against Aedes aegypti for years. Since 2009 Insect Growth Regulators (IGR) are also employed in the control of larvae. We quantified resistance to temephos (OP), deltamethrin (PY), and diflubenzuron (IGR) of A. aegypti samples from 12 municipalities distributed throughout the country, collected between 2010 and 2012. High levels of resistance to neurotoxic insecticides were detected in almost all populations: RR95 to temephos varied between 4.0 and 27.1; the lowest RR95 to deltamethrin was 13.1, and values higher than 70.0 were found. In contrast, all samples were susceptible to diflubenzuron (RR95 < 2.3). Biochemical tests performed with larvae and adults discarded the participation of acetylcholinesterase, the OP target, and confirmed involvement of the detoxifying enzymes esterases, mixed function oxidases, and glutathione-S-transferases. The results obtained were discussed taking into account the public chemical control component and the increase in the domestic use of insecticides during dengue epidemic seasons in the evaluated municipalities.

Insecticide resistance, associated mechanisms and fitness aspects in two Brazilian Stegomyia aegypti (= Aedes aegypti) populations

“…The resulting strain presented reduced alteration of detoxifying activity, but was still highly resistant to pyrethroids. However, insecticide resistance is a multifactorial and complex phenomenon, in which each population uses 'local solutions' to deal with the challenge of insecticide (Viana-Medeiros, 2011;Bellinato et al, 2016). Such solutions have close relationships with the changes in metabolic resistance enzymes, which are likely to have been preselected in previous challenges in field larval breeding sites (Mallet, 1989;Belinato & Martins, 2016).…”

Variation in temephos resistance in field populations of Aedes aegypti (Diptera: Culicidae) in the State of Sergipe, Northeast Brazil

“…Due to the continued use of temephos throughout the world, many populations of Ae. aegypti were reported to be resistant not only in Brazil [4][5][6][7][8][9][10][11] , but in several other countries [12][13][14][15] , as well. In 1999 and 2000, populations of Ae.…”

“…However, a disadvantage to these insecticides is related to the acetylcholinesterase binding sites. This enzyme hydrolyzes acetylcholine molecules, resulting in an exacerbation of nerve impulse transmission and results in the paralysis and death of a target insect 9 , but this enzyme is also present in vertebrates 5,9 . In addition, its effectiveness depends on many factors, such as water turnover rate, as well as environmental factors, such as organic debris, temperature, and exposure to sunlight 19 .…”

“…As a consequence of the high degree of resistance, the Brazilian Ministry of Health initially promoted its replacement by products based on Bacillus thuringiensis (Bti) in regions with reported resistance 16 ; these were subsequently replaced by growth inhibitory products, such as inhibitors of chitin synthesis and juvenile hormone analogs 22 . However, products used to replace temephos have the disadvantage of short residual effects 6 , which necessitates periodic reapplication, and they do not cause immediate mortality in larvae, but rather mortality occurs at the pupal stage or during the emergence of an adult 9 . This latter fact makes it necessary to modify the method of estimating mosquito infestation, as the House Index may be overestimated in treated areas 23 .…”

Control of Vector-Borne Human Parasitic Diseases

“…Its control is the main tool available to fight transmission of diseases such as dengue, Zika, or chikungunya. Bellinato et al [12] bring us an overview of the resistance profile of A. aegypti to several insecticides in Brazil, the country most affected currently by dengue and Zika virus.…”