MALARIA AND BEDNETS

• Mosquito nets made of silk were first used by the Chinese, and they were brought to Japan more than a thousand years ago. Mosquito nets made from hemp became popular in Japan in the 17th century.
• Anti-malaria bednets, treated with DDT, were first used during World War II by the Russian, German and US armies.
• In the late 1970s, synthetic pyrethroids were developed to mimic natural insecticidal compounds found in chrysanthemums. Pyrethroids are widely used as household insecticides and are effective against mosquitoes. Unlike DDT, for example, pyrethroids such as permethrin do not accumulate in the food chain and are rapidly broken down in both sunlight and the soil.
• The World Health Organization's interest in mosquito nets began in the early 1980s. It has given its approval to the use of pyrethroids in general and of permethrin in particular for the treatment of bednets.
• IDRC is funding a project in Tanzania to test the effectiveness of insecticide-treated bed curtains made from locally available sacking material used for agricultural products. The research was in response to promising results from community trials of insecticide-treated mosquito nets and interest in substituting locally available material.
• Impregnated Bednets and Community Prevention of Malaria (Benin) is an ongoing IDRC project begun in 1992 to evaluate mosquito nets treated with permethrin and to examine the feasibility of integrating bednets into other components of a malaria control and primary health care strategy.
• IDRC's bednet project in Benin led to the identification of Rentex Inc. of Montreal as a supplier of the material used for bednets. Rentex produces polyester material for a variety of apparel and agricultural uses and was able to create a suitable fabric for bednets used in the project.
• Rentex worked in collaboration with the McGill University Centre for Tropical Medicine at the Montreal General Hospital to create a strong, durable netting that would last for five years. The 100% polyester netting was designed and woven to have the appropriate hole size to ensure protection from mosquitoes while providing sufficient ventilation.

• The Benin project is examining community participation in the local production, distribution and use of bednets, as well as variables pertaining to the process of periodically treating the bednets with insecticides.
• Rentex is now producing a stronger material made from high density (HD) polyethylene that is expected to last 20 years. The company is researching the incorporation of insecticide into the fabric to be effective for up to two years. The conventional nets need to be retreated every six months.
• Permethrin is now being used as the insecticide for bednet treatment with a dose of up to 500 milligrams per square metre of net. IDRC has funded research to develop effective methods for the production and distribution of bednets and to prolong the insecticidal effects while ensuring the safety of the insecticide impregnation process.
• The results from the first mortality study of insecticide-impregnated mosquito nets in The Gambia showed a reduction in deaths from all causes in children under the age of five of 63%. (Lancet 1994; 344: 1175-82)
• The mortality study in the Gambia prompted the Malaria Intervention for Child Survival program, begun by IDRC in 1993, in collaboration with WHO. Trials were conducted in Burkina Faso, The Gambia, Ghana, and Kenya to confirm the efficacy of bednets to reduce mortality.
• The results of the second study in The Gambia confirmed the earlier study results showing a reduction in mortality of 25 to 38% in children under 9 years of age. (Lancet 1995, 345: 479-83)
• More than 20 studies of insecticide-treated nets (ITNs) have been conducted in different areas of the world where malaria is endemic. Most studies have documented a reduction in malaria disease rates between 20 and 63% following the introduction of ITNs.
• The results from two large-scale trials in Kenya and Ghana, funded primarily by WHO and IDRC/CIDA, are now available and demonstrate a substantial impact on child survival. These studies, also supported by a number of other international development organizations, are helping to define new research priorities and strategies for the effective implementation of ITN programmes.

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