Global plan for insecticide resistance management in malaria vectors

Annex 5 Example of ‘tippingpoint’in resistant AedesmosquitoesThe evolution of kdr resistance to pyrethroids in Aedes mosquitoesin Mexico demonstrates the ‘tipping-point’ concept. Between2000 and 2003, the frequency of resistance was very low (≤ 10%)at most sentinel sites. At some time between 2003 and 2007,however, because of continuous selection pressure from thesame insecticide, the tipping-point was reached, and resistanceincreased significantly in six sites, reaching frequencies of ≤ 80%by 2007 (Figure A5.1).Figure A5.1: Frequency of kdr resistance to pyrethroids in Aedes mosquitoes in Veracruz, Mexico, 2000-2007Low levels of resistance between 2000and 2003: 2–3% in most placesSignificant increase in level of resistanceat almost all sites by 2007: up to 80% insome areas.From J Hemingway and Liverpool School of Tropical MedicineThis map has been reproduced with the agreement of the original author.113