Introduction

7. The Use of POPs in Malaria Control: The Search for Alternatives

by Dr. Mambu Ma-Disu

Introduction

Since the beginning of time, the parasitic infectious disease of malaria due to the plasmodium carried by mosquitoes of the genus anopheles, wreaks havoc in the areas where is endemic.

This disease, while it is on the decrease in developed countries, continues to be one of the main concerns of developing countries.

WHO statistics estimate that there are between 300 and 500 million cases of malaria every year, causing 1.05 to 2.7 million deaths. 90 per cent of these cases occur in Africa south of the Sahara.

As is the case with other endemic countries, Mali does not escape from attacks of this disease; the 1996 Statistical Annual gives a specific death rate of 1.16 per cent, and 31.64 per cent of medical consultations are due to this disease.

The fight against this scourge is carried out through the National Malaria Control Programme (PNLAP) and uses several strategies, including vector control through the use of various insecticides with various secondary effects.

The aim of what follows is to make proposals for alternatives starting from current practices.

Malaria control strategies

The years of experience of trying to control this disease have given rise to a range of strategies, from creating a barrier between the host and the vector to the use of various medicines.

Major current strategies are:

* Diagnosis and early treatment of simple and serious cases with medicines which have various results and effects. The products mainly used are chloroquin tablets, quinine, sulphadoxine-pyrimethamine ...;

* Chemical prophylaxis for pregnant women groups weakened by their condition. They receive a weekly treatment with products which prevent them having an attack of malaria;

* The use of insecticides to destroy the vector or to avoid its contact with man;

* Prevention and control of epidemics in areas at risk.

The use of insecticides

Throughout the world many different insecticides are used for malaria control causing difficulties in complying with established standards. This is an area in which many actors intervene, in the manufacturing, distribution and dispensation of aid.

In Mali, a varied range of insecticides is used, with varying modes of action and harmful effects. The main ones used are:

. Diazinon

. Durban or chlorpyriphos ethyl

. Cyhalon or cyfluthrine

. Cypermethrine

. Propoxur

. Permethrine, the most used at present for the impregnation of mosquito netting, with a persistence of 4 to 6 months;

. Icon 2.5 cs or Lambda-cyhalothrin, recently proposed, with a persistence of 18 months.

The major disadvantage of these insecticides is the risk of intoxication, their persistence in the environment, with slow or variable biodegradation, and the risk of the development of resistance on the part of mosquitoes.

It seems that some such as permethrine or lambda do not have these disadvantages or at least have them to a lesser degree.

Alternatives to the use of insecticides

In reference to the harmful effects quoted above, for many years man has been searching for better and less harmful methods of controlling malaria. At present there is no completely satisfactory method.

Possible approaches are:

. Sanitation of the environment, requiring a healthy environment resulting from sound town planning works, preventing the hatching of mosquitoes and their larvae. In Mali, lime slurry has been used and appears to be effective in controlling larvae;

. The search for vaccines that are sufficiently effective and low-priced to be used on a large scale. Despite a few glimmers of hope in this area (the Colombian vaccine), little progress has been made. For a vaccine to be considered as effective, it should enable 80 per cent of the population to be protected during a period of at least one year;

. Biological control, which consists in using the toxigenic powers of strains of the bacteria bacillus thurengiensis, fish (minnows) and aquatic mushrooms, against mosquito larvae;

. Information and awareness-raising of manufacturers, distributors, suppliers and the general public to encourage compliance with standards of conservation and use of insecticides.