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.
