Now, the disease has been all but eradicated from parts of the African continent with the help of a novel artificial cow.

Developed by an international group of researchers including scientists from the University of Greenwich in the UK, the artificial cows attract tsetse by using kairomones (a blend of chemicals emitted by one species and detected by another) to mimic the smell of real cattle.

The fake cattle are impregnated with insecticides that kill the tsetse attracted to them.

These artificial cows were introduced into Zimbabwe in the mid-1980s, when thousands of cattle were infected with Nagana, transmitted by tsetse.

Cases of Nagana in Zimbabwe have plummeted to practically zero and have remained at this low level for the last five years, largely due to the use of artificial cows, of which there are now about 60,000 in use. The fake cows also act as an effective barrier to stop tsetse re-invading areas cleared of flies.

Not only are artificial cows highly successful in controlling tsetse, but their use also results in a dramatic reduction in the amount of insecticide necessary to control this pest.

With only four artificial cows needed per square kilometer to ensure effective pest control, the use of insecticide is far more targeted than conventional widespread aerial and ground spraying, resulting in a greatly reduced environmental impact.

"During the mid-1980s, when cases of Nagana were at their peak in Zimbabwe, the government was spraying 100-200 tons of the DDT pesticide per year (now banned in many countries) to control the tsetse fly population," says Dr. Stephen Torr of the University of Greenwich's Natural Resources Institute. "In total, around 2,900 tons of DDT have been used in Zimbabwe. This pest control policy has now been abandoned in favor of more effective and environmentally-friendly alternatives such as artificial cows."

Sleeping sickness, spread by the tsetse fly, is rife in Africa, threatening over 60 million people in 36 countries, according to the latest World Health Organization (WHO) statistics. Without treatment, the disease is fatal. There have been three severe epidemics of sleeping sickness in Africa over the last century, with the last one beginning in 1970 and still in progress.

Sleeping sickness and Nagana are transmitted to humans and cattle by tsetse infected with a parasite called Trypanosoma. These parasites multiply in the blood, initially causing bouts of fever and joint pain.

If left unchecked, they can cross the blood-brain barrier and infest the central nervous system. This can lead to confusion, sensory disturbances, irreversible brain damage and eventual death.

The effects of Nagana on cattle are equally devastating. Found over an area of 10 million square kilometers in Africa, the disease is a major constraint on agricultural development in many poor countries, and is estimated to infect 46 million cattle in Africa alone and cause three million cattle deaths a year.

"We believe that these artificial cows (developed with funding from the Department for International Development and the EU) could significantly reduce cases of Nagana," says Dr. Torr.

20-Sep-2001