Spatial and temporal country-wide survey of temephos resistance in Brazilian populations of Aedes aegypti

Abstract

The organophosphate temephos has been the main insecticide used against larvae of the dengue and yellow fever mosquito (Aedes aegypti) in Brazil since the mid-1980s. Reports of resistance date back to 1995; however, no systematic reports of widespread temephos resistance have occurred to date. As resistance investigation is paramount for strategic decision-making by health officials, our objective here was to investigate the spatial and temporal spread of temephos resistance in Ae. aegypti in Brazil for the last 12 years using discriminating temephos concentrations and the bioassay protocols of the World Health Organization. The mortality results obtained were subjected to spatial analysis for distance interpolation using semi-variance models to generate maps that depict the spread of temephos resistance in Brazil since 1999. The problem has been expanding. Since 2002-2003, approximately half the country has exhibited mosquito populations resistant to temephos. The frequency of temephos resistance and, likely, control failures, which start when the insecticide mortality level drops below 80%, has increased even further since 2004. Few parts of Brazil are able to achieve the target 80% efficacy threshold by 2010/2011, resulting in a significant risk of control failure by temephos in most of the country. The widespread resistance to temephos in Brazilian Ae. aegypti populations greatly compromise effective mosquito control efforts using this insecticide and indicates the urgent need to identify alternative insecticides aided by the preventive elimination of potential mosquito breeding sites.

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

“…The use of Aracaju as a sentinel city may have obfuscated the spread of the resistance, delaying the replacement of temephos and leading to an intensification of temephos resistance in the region. Variation in mosquito resistance in closed cities has been seen in other areas in the country 4,7,8 . Because of the large variability in the level of resistance, it is likely that sentinel sites cover an area smaller than expected, considering the values in Sergipe, and this should be taken into account in resistance surveillance plans.…”

“…aegypti populations in Sergipe, as well as in other areas in the country [5][6][7][8] , may be related to how temephos is used in each locality. It may be used at different intensities and frequencies, and the mosquito populations could be under different selection pressures.…”

“…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.…”

“…Thus, the use of temephos in Brazil has been suppressed since 2009, with the belief that it could reverse the spread of resistant populations 7 . 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 .…”

Análise do controle vetorial da dengue no sertão piauiense entre 2007 e 2011

“…Fatores biológicos e antropogênicos são atribuídos à mudança na epidemiologia da dengue e no comportamento do vetor, tais como: mudanças demográficas em populações humanas, urbanização, velocidade e volume de tráfego internacional, introdução de novos genótipos da dengue, fracasso dos programas de controle de vetores devido à resistência aos inseticidas, prática de má gestão e picos sazonais na população do vetor e da dengue, além de fatores climáticos, como o aquecimento global e os fenômenos El Niño e La Niña, que influenciam na intensidade das chuvas e produzem alterações da biodiversidade nas regiões intertropicais, facilitando a permanência do vetor [4][5][6] . As consequências de uma epidemia de dengue são sentidas em diversas áreas sociais, tais como a economia, a educação e, principalmente, a saúde 7,8 .…”