Effect of the type and number of washes in the efficacy of long lasting insecticidal nets for Aedes aegypti control in Girardot, Colombia.

Introduction: The use of long lasting insecticidal materials has shown promising results in the control of Aedes aegypti. Objective: To evaluate the efficacy of long-lasting insecticidal nets PermaNet (R) for Aedes aegypti control after three washing treatments in Girardot - Cundinamarca. Materials and methods: Standard bioassays were conducted with the nets following the World Health Organization protocols using wild A. aegypti after three washing treatments: (1) Detergent powder, (2) Detergent powder and bleach, (3) Bar soap, until complete 20 washes. Results: There were differences between wash treatments and number of washes. Greater effects in the insecticide bioavailability were seen for the bar soap treatment. After six washes, mortality decreased by 50% (25/50), vs 66% (33/50) for the detergent powder and 84% (42/50) for the detergent powder and bleach treatments. Regarding the number of washes, with only three washes the efficacy of the bar soap treatment was reduced at 68%. Conclusion. The effectiveness of the Long-lasting insecticidal nets (PermaNet 2.0) for A. aegypti control varies in relation to the treatment and number of washes. The bar soap treatment presented greatest mortality effects. Further studies on insecticidal reductions are needed under local conditions.