Insecticide Resistance

We drive research and development toward new solutions, mobilizing resources around effective insecticide resistance management.

Insecticide resistance is the greatest current threat to the future of malaria control and to the sustainability of the achievements of recent years, according to Pedro Alonso, Head of the WHO Global Malaria Program, 2015.

It is important to note that insecticides do not create resistance – they do not generate mutations in insects which then become expressed as resistance. The resistant traits or ‘mutations’ are present in the insect population already at very low levels. Insecticides represent a selection pressure which allows resistant individuals to build up in numbers within a given population if the selection pressure is repeatedly applied. Selection for, and development of, insecticide resistance is a real and pending threat, especially in areas where monitoring resistance management strategy is not pro-actively implemented.

The biggest problem currently faced by the vector control community is the heavy reliance on only four different chemical classes of insecticides:

  1. organochlorines (OC) – e.g. DDT
  2. organophosphates (OP) – e.g. pirimiphos-methyl, malathion
  3. carbamates (CAR) – e.g. bendiocarb
  4. pyrethroids (PY) – e.g. deltamethrin, cyfluthrin, permethrin, lambda-cyhalothrin

These four groups of insecticides act on only two different target sites and represent only three modes of action. OPs and CAR both inhibit the activity of the enzyme acetylcholinesterase, however, carbamates differ from OPs in that the inhibition is reversible. Pyrethroids and DDT are modulators of voltage-gated sodium channels.

Developing knowledge about the types of resistance which may be present in a mosquito population is important in order to make informed decisions about the selection of an effective insecticide. For example, in situations where high levels of kdr resistance in mosquito populations are present, the rotation of pyrethroids with Ficam (a carbamate) has proven to provide successful disease control.

The science of Resistance Prevention and Management has become one of Bayer’s key considerations in developing new products and initiatives worldwide and already has a new mode of action under evaluation with the WHO Pesticides Evaluation Scheme.