A truly sacred cow

The tsetse fly is one of Africa's most harmful pests carrying fatal sleeping sickness (trypanosomiasis) and nagana (the equivalent disease in cattle) caused by a protozoan but could soon be completely eradicated from parts of the continent thanks to an artificial cow.

Scientists from the University of Greenwich, UK, working with international colleagues have built an artificial cow that attracts the tsetse fly using kairomones (a blend of chemicals emitted by one species and detected by another - the inter-species equivalent of pheromones). The kairomones mimic the smell of real cattle and attract the tsetse to the fake cow, which is loaded with pesticide.

	Stephen Torr

Since the introduction of the artificial cows in Zimbabwe thousands of cattle have been saved from nagana infection.

One important spin-off of the work is that by controlling the tsetse fly in this way, insecticide requirements have fallen dramatically. Four artificial cows are needed per square kilometre to be effective and the insecticide used is much more targeted than conventional widespread aerial and ground spraying. "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," says Greenwich's Stephen Torr, "This pest control policy has now been abandoned in favor of more effective and environmentally-friendly alternatives."