Anopheles gambiae is the main malaria-carrying mosquito in Africa. It enters houses through the open eaves of over-hanging roofs. Could changes in house design reduce the spread of malaria? Researchers from the UK University of Durham and the Medical Research Council tested different hut modifications in the Gambia.

Malaria control is currently based on treatment of illness and personal protection against mosquitoes using insecticide-treated bednets or indoor spraying. But other strategies may be just as effective. House screening helped to eliminate malaria from many parts of the world. The researchers compared six huts with different modifications:

• traditional design
• plywood ceiling
• synthetic netting ceiling
• insecticide-treated synthetic netting ceiling
• plastic insect screen ceiling
• eaves closed with mud.

Their results show that a ceiling reduces the entry of Anopheles gambiae. Synthetic netting or plastic insect screens are more effective than plywood (78-80 per cent reduction versus 58 per cent). This degree of protection is similar to the effect of using insecticide-treated bednets in the same huts. However, closing the eaves does not have a significant effect. Ceilings also reduce entry by Mansonia mosquitoes which spread lymphatic filariasis and various viruses. The reduction is similar if the netting is treated with insecticide, but protection might be improved if insecticide is applied to curtains around the door and windows. Houses with closed eaves or a wooden ceiling are a little hotter than the other houses, whereas netting and insect-screen ceilings may be stuffier than control huts.

The researchers also interviewed 128 Gambian adults – 54 men and 74 women. They found that:

• People feel that ceilings improve the functioning and look of houses and reduce disturbance by mosquitoes.
• Less than 20 per cent of houses have ceilings or closed eaves.
• The cost of materials and the extra effort required limit the use of ceilings in house construction.

However, all the structural changes made to the huts are cheap: almost free for closing eaves or £0.36-0.59/person/year for locally made ceilings, which last three to five years. Ceilings could be an effective way to prevent malaria in places where people are reluctant to use nets because there are few nuisance mosquitoes. The researchers recommend that policy-makers should consider including ceiling construction as part of an integrated approach to malaria control.

Source(s):
‘Changes in house design reduce exposure to malaria mosquitoes’, Tropical Medicine and International Health 8 (6): 512-517, by S.W. Lindsay, et al, 2003
'Reducing malaria by mosquito-proofing houses', Trends in Parasitology 18: 510-514, by S.W. Lindsay et al, 2002

id21 Research Highlight: 13 November 2003

Further Information:
Steve Lindsay
Institute of Ecosystem Science
School of Biological and Biomedical Sciences
University of Durham
Science Laboratories
Durham DH1 3LE
UK

Contact the contributor: s.w.lindsay@durham.ac.uk

University of Durham, UK

Medical Research Council Laboratoires, Gambia

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