Simulating dynamic insecticide selection pressures for resistance management in mosquitoes assuming polygenic resistance
Fig 3
An example insecticide decay profile for an ITN.
In this example the insecticide is deployed at its manufacturers recommended concentration with an initial deployed insecticide efficacy of =1. It is a two-step function. Step 1 describes the first two years (~20 mosquito generations) as the insecticide decays slowly at its base decay rate (blue line). Step 2 occurs after the decay threshold (
) has been reached (vertical yellow line) and the insecticide efficacy decays rapidly (red line). In this example the base decay rate
was 0.015, the rapid decay rate
was 0.08 and the decay threshold
was 20 generations (~2 years). These values are user-defined inputs and can be varied allowing insecticides to decay faster/slower or sooner/later. Setting
and
to 0 prevents insecticide decay from occurring (a key assumption in previous models). Insecticides in mixture can have different decay properties. Setting decay rates to be identical before and after the threshold eliminates the second phase and converts the decay profile to a single dynamic if required.