[Susceptibility of Aedes aegypti larvae to the insecticide temephos in the Federal District, Brazil].
OBJECTIVE
To study the susceptibility status of Aedes aegypti to the organophosphate insecticide temephos.


METHODS
Samples of Ae. aegypti larvae were obtained, using ovitraps, from eight cities of the Federal District, central Brazil, in 2000 and 2001. Larvae were submitted to the diagnostic dose of 0.012 mg/l temephos, as recommended by standard World Health Organization methodology. Field populations were tested in parallel with reference strains Rockefeller and DIVAL, from the Environmental Surveillance Directory (DIVAL) insectary. The concentration and purity of temephos solutions were verified by gas chromatography. Correlation calculations were performed using StatView - SAS Institute Inc., version 5. Student's t test was used for detecting differences in susceptibility, with significance levels of alpha=0.05.


RESULTS
In 2000, Ae. aegypti larvae populations from Taguatinga, Guara, and Nucleo Bandeirante showed resistance to temephos, with mortality ranging from 54.1 to 63.4%. The populations from Gama, Planaltina, and Sobradinho showed altered levels of susceptibility (mortality ranging from 83.6 to 92.8%). The population from Ceilandia was the only susceptible one, with 98% mortality. In 2001, all populations tested were resistant (44.4 to 66.4% mortality). No significant correlation was found between the susceptibility of populations and the distance between the cities of origin, or the amount of insecticide applied in the years preceding the study.


CONCLUSIONS
Ae. aegypti susceptibility to temephos is changing in the Federal District. It is essential to continue monitoring the resistance of this vector to insecticides in order to ensure the efficiency of programs aimed at vector control and at the protection of human health.
Carvalho
Maria do Socorro Laurentino de
Mdo S
Vigilância Ambiental do Distrito Federal, Brasília, DF, Brazil. mslcarvalho@abordo.com.br
Caldas
Eloísa Dutra
ED
Degallier
Nicolas
N
Vilarinhos
Paulo de Tarso Ribeiro
Pde T
Souza
Luís César Kenupp Rodrigues de
LC
Yoshizawa
Maria Amélia Cavalcanti
MA
Knox
Monique Britto
MB
Oliveira
Cristiane de
Cd
D000330:Aedes; D000818:Animals; D001938:Brazil; D006801:Humans; D007303:Insect Vectors; D007306:Insecticides; D007814:Larva / Q000187:drug effects; D009032:Mosquito Control; D012621:Seasons; D000002:Temefos
D007306:Insecticides; D000002:Temefos