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Bulletin of the World Health Organization

Print version ISSN 0042-9686

Bull World Health Organ vol.78 n.10 Genebra Jan. 2000 

New fly trap may reduce prevalence of blindness from trachoma

Home-made fly traps using old plastic bottles and faeces may significantly reduce the prevalence of trachoma, a disease that is a major cause of blindness in the developing world. Results of tests of the devices in Kenya have shown the traps can reduce household fly populations by almost half, and the numbers of cases of trachoma by more than one-third.

According to the World Health Organization, which three years ago launched a programme to eliminate trachoma by 2020, the disease has resulted in blindness in around six million people in the world. Trachoma is a bacteria-related infection that is one of the world’s leading causes of blindness. Cumulative attacks by Chlamydia trachomatis result in local tissue inflammation and a sticky mucous is produced. This can lead to a tightening of the eyelid, making it bend inwards, and the eyelashes may damage the surface of the cornea. In some cases, this may lead to eventual blindness.

The latest technique, the development of which was supported by the Royal College of Surgeons in Ireland, is based on an original idea from Professor David Morley, a retired specialist in tropical child health at the Institute of Child Health in London, and Dr Michael Elmore-Meegan of the International Community for the Relief of Starvation and Suffering (ICROSS). The device uses two transparent drink bottles, mounted one above the other, to create a fly trap and exploits the concept that once they have had a meal, flies almost always fly upward and towards the brightest available light.

In the trap, the flies are first lured through the fly ‘ports’ into the bottom bait bottle, which is covered with mud so that it is dark on the inside, or with dark paint poured in and distributed evenly by twisting the bottle. The bait in this lower bottle is early morning breastfed baby’s stool and urine or milk that has gone sour. After eating, the flies move up through a tube attracted by the light emitted from the transparent bottle above which must be small ventilation slits or holes. Once in the upper bottle, the insects will stay until they die of exhaustion.

After a year long trial of the traps in 300 Maasai homes in Kenya, researchers reported that the fly population decreased by 40%. At the same time, the number of cases of trachoma decreased by 36%.

One big advantage of the traps, if they do prove to be effective in the long term, is that they are cheap to produce. According to Professor Morley, Maasai children were able to make the traps as part of a homework project at very low cost.

Roger Dobson, Abergaveny