A. Introduction

Since the introduction of DDT forty years ago, numerous chemical products have been invented for the destruction of disease vectors and agricultural insect pests.

Two major problems have appeared:

- Many insects vectors have developed a resistance to these products.
- Their human toxicity has, at times, caused serious public health problems.

In the context of the work of Medecins Sans Frontieres we are confronted by these problems in several ways:

- in the course of medical treatment after poisoning,
- as users during a specific vector control programme,
- as trainers in public health.

This chapter should, within the limited context of our actions, allow us to choose and to use suitably some selected insecticides, to know the precautions for their use and finally to be able to take emergency medical action in the case of poisoning.But it is also intended as a warning against the apparent ease of use and effectiveness of these products.

The use of pesticides is costly, is never without risk and is not always effective. In the context of a medical programme it may be conceived:

- either in an emergency phase (an epidemic due to a vector),
- or when the control of vector breeding sites is a problem (difficult to locate, far away, etc.).

Chemical control should always be planned alongside a programme of improvement of the site and/or of general living conditions and hygiene (the removal of stagnant water and refuse, scrub clearance, reduction of living density, water and sanitation services, etc.).

If no action is taken in this direction even the most active and powerful insecticide would have little impact in the long term.

The pesticides are frequently used in agriculture often, however, the users are not informed of the precautions to take during the transport and use of these products. The health problems which result may go unnoticed because the poisoning is chronic.

Here again, the remedy is prevention: information and education.