[Susceptibility of Aedes aegypti to DDT, deltamethrin, and lambda-cyhalothrin in Colombia].
OBJECTIVE
To assess the susceptibility status of 13 natural populations of Aedes aegypti (collected from sites in Colombia where dengue is a serious public health problem) to the pyrethroids, deltamethrin and lambda-cyhalothrin, and to the organochlorine, DDT, and to identify any biochemical mechanisms associated with resistance.


METHODS
Immature forms of the vector were collected from natural breeding spots at each site and then raised under controlled conditions. Using the F2 generation, bioassays were performed using the World Health Organization's 1981 methodology (impregnated paper) and United States Centers for Disease Control and Prevention's 1998 methodology (impregnated bottles). In populations where mortality rates were consistent with decreased susceptibility, levels of nonspecific esterases (NSE), mixed-function oxidases (MFO), and acetylcholinesterase (AChE) were measured using colorimetric tests.


RESULTS
All of the mosquito populations that were tested showed resistance to the organochlorine DDT. In the case of the pyrethroids, widespread resistance to lambda-cyhalothrin was found, but not to deltamethrin. Assessing the biochemical resistance mechanisms showed that 7 of the 11 populations had elevated NSE, and one population, increased MFO.


CONCLUSIONS
Physiological cross-resistance between DDT and lambda-cyhalothrin in the A. aegypti populations tested was dismissed. Physiological resistance to lambda-cyhalothrin appears to be associated with increased NSE. The differences in susceptibility levels and enzyme values among the populations were associated with genetic variations and chemicals in use locally.
Santacoloma Varón
Liliana
L
Laboratorio de Entomología-Red Nacional de Laboratorios, Instituto Nacional de Salud de Colombia, Bogotá, Colombia. lisantacoloma@gmail.com
Chaves Córdoba
Bernardo
B
Brochero
Helena Luisa
HL
D000110:Acetylcholinesterase / Q000032:analysis; D000330:Aedes / Q000201:enzymology; D000818:Animals; D001681:Biological Assay; D043182:Carboxylesterase / Q000032:analysis; D003105:Colombia; D003124:Colorimetry; D003634:DDT; D004351:Drug Resistance; D018432:Drug Resistance, Multiple; D019476:Insect Proteins / Q000032:analysis; D007306:Insecticides; D006899:Mixed Function Oxygenases / Q000032:analysis; D009032:Mosquito Control; D009570:Nitriles; D011722:Pyrethrins
D019476:Insect Proteins; D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin; D003634:DDT; D006899:Mixed Function Oxygenases; D043182:Carboxylesterase; D000110:Acetylcholinesterase; C037304:cyhalothrin