1. Introduction

Malaria continues to be a major public health problem in many endemic countries and is one of the major causes of morbidity and mortality in sub-Saharan Africa. It is estimated that malaria causes from 300 to 500 million clinical cases, and 1.5 to 2.7 million deaths worldwide each year, with 80 to 90% of the clinical cases and one million deaths occurring in Africa alone. Malaria also considerably affects the health of children, leaving sequelae, increasing susceptibility to other infections and hampering their development. Even non-fatal cases have severe consequences. The disease is associated with considerable economic burden, including direct cost to governments and patients for hospital admissions and outpatient consultations, cost to households for treatment sought outside the official system, and cost due to absenteeism from productive work, or education.

The governments concerned have decided to intensify efforts to deal with the malaria problem in Africa and have agreed to implement the Global Malaria Control Strategy (GMCS) endorsed at the Ministerial Conference in Amsterdam (1992).

The GMCS advocates four technical measures:

· to provide early diagnosis and prompt treatment; · to plan and implement selective and sustainable preventive measures, including vector control; · to detect early, contain or prevent epidemics; · to strengthen local capacities in basic and applied research to permit and promote the regular assessment of a country's malaria situation, in particular the ecological, social and economic determinants of the disease.

The implementation of the vector control component involves the selective use of methods based on personal protection, use of insecticides, environmental management, and biological control. Insecticide-treated mosquito and other materials (ITMNs) are options combining one aspect of personal protection (mosquito nets) with insecticides.

The inherent tendency to avoid insect bites and disturbances often prompts people to resort to physical and/or chemical means. Records on the use of mosquito nets date back to the 6^th century B.C. They have been used for decades as protection against nuisance insects, dust and roof debris falling on sleepers as well as for privacy. Nets, curtains and clothing impregnated with insecticides have been used even during the Second World War to protect from malaria and other vector-borne diseases. DDT impregnated bednets were among the malaria control tools used in the 1950s; their utilization was short-lived due to the introduction of malaria eradication approaches. The potential usefulness of insecticide-treated mosquito nets (ITMNs) in malaria control was reconsidered in the 1980s with the advent of the photostable synthetic pyrethroids.

Large-scale implementation of ITMNs as part of an integrated approach to malaria control started in the WHO Western Pacific Region in the 1980s. The practical experience thus gained highlighted the need, for adaptation to local conditions, appropriate resources, and local capacities, and the importance of addressing the managerial and operational issues relevant to large-scale implementation, including community and intersectoral actions, and decentralization. In the African Region, ITMNs application is recognized as one of the three key elements i.e. i) appropriate case management, ii) use of insecticide-impregnated bednets and other materials, and iii) strengthening of local and national capabilities, which form the basis for intensified malaria control (AFR/RC45/R4: Resolutions of the Regional Committee for Africa, Regional Programme on Malaria Control, 1995).

Studies have been carried out on the short-term efficacy of pyrethroid-treated mosquito nets on malaria vectors and disease in many parts of the world; some with positive results, others inconclusive or contradictory. However, recently, four randomized controlled large-scale field trials in Africa have shown that appropriate use of insecticide-treated bednets can reduce mortality among children aged 1-4 years by 17-33% (average 25%) depending on the site; thus clearly demonstrating opportunities for significant improvements in child survival through the use of ITMNs. The results of the studies were reviewed at a meeting on insecticide-impregnated materials (Brazzaville, 18-20 March 1996). The recommendations made included the strategic introduction of ITMNs to high risk groups wherever possible, taking into account the experience gained in programmes that are being implemented. This, in addition to ITMNs already being a key element of intensified malaria control in Africa, has led to the development of these guidelines to support their implementation.

So far, the experience gained in the implementation, especially on a large-scale is limited in Africa. Many managerial and operational aspects involved in their delivery and financing, as well as the overall issues of sustainability are not yet ascertained. The implementation (within the framework of the intensified malaria control strategy) in Africa therefore has to be phased and closely monitored and the various issues of sustainability addressed. The programme expansion is to benefit from the experience gained in the implementation, and the outcome of further research including the issues in relation to immunity.