Fighting flies with fancy

RESEARCHERS in Zimbabwe have found an effective way to deal with tsetse flies. The novel solution, which is simple, cost-effective, efficient and environ- ment-friendly, was first devised by the Rekomitjie research station in the Zambezi Valley in northern Zimbabwe.

The research team discovered that tsetse flies are attracted by both visual stimuli and odours. With assistance from scientists in Europe, particularly the Natural Resources Institute in the UK, they succeeded in reproducing cattle odours artificially. These are placed in plastic sachets or bottles and fixed to insecticide- treated coloured targets in tsetse-infested areas like Hurungwe. These 'stuffed warthogs', made of blue and black canvas, can be seen dotting the countryside.

The fly is attracted to blue, but prefers black surfaces. Attracted by the smell and look of the blue cloth, the flies nevertheless land on black panels that are treated with an insecticide. They flyaway, only to drop dead nearby - simple, effective and environmentally clean.

The tsetse fly is unusual in that, in many ways, it is more like an animal than an insect. Glyn Vale, research coordinator for the Regional Tsetse and Trypanosomiasis Control Programme (RTTCP), describes it as a "little lion" which feeds on blood every two to three days. A fly becomes a carrier of trypanosomes - the organisms causing sleeping sickness among humans - by feeding on the blood of an infected domestic or wild animal. It may then pass on the disease to every animal on which it feeds during its lifetime.

The fly infests about 10,000,000 sq krn of warm and humid tropical Africa and is a serious obstacle to rural development, causing a disease called nagana in cattle and sleeping sickness in humans. Infected cattle become weak and unable to pull ploughs, while fertility and milk production decline rapidly.

Despite the huge area infested by the fly, the new techniques have been highly successful. According to Vitalis Chadenga, assistant director of the Zimbabwe tsetse and trypanosomiasis control branch, cases of trypanosomiasis in cattle in the country fell from 15,000 in 1986 to 300 in 1995. "There has been a tremendous decline in cases of nagana and sleeping sickness in areas infested by the flies," says Chadenga.

The tsetse control programme, launched in 1986, has been funded by the European Union. Around the time the war for Zimbabwe's independence came to an end, large areas in the northern, northeastern, eastern and southeastern parts of the country had been invaded by flies from Mozambique and Zambia. Other civil wars and economic constraints in other countries in southern Africa have also hampered efforts to control the tsetse. While Zimbabwe led the effort, other nations also realised that the problem was not defined by national boundaries and that a regional approach was required. This led to the formation of the RTTCP, which covers Malawi, Mozambique, Zambia and Zimbabwe.

"It was a formidable task, covering the 322,000 sq km-spread in Zambia, Malawi, Mozambique and Zimbabwe which is infested with the fly," says Robert Connor, regional coordinator for the RTTCP. Linking tsetse control with sustainable rural development programmes was of utmost importance, he notes. Once an area becomes open to agricultural development after removal of the tsetse, demand for the arable land rises fast. Often, there is a huge influx of people and cattle into the area, resulting in over-grazing and other damage to the fragile environment.

Various control methods were used over the years, including slaughter of wild animals whose blood the tsetse fed on, removal of vegetation in which the flies sheltered, and ground and aerial spraying of insecticides over wide areas.

The last proved very successful, but caused increasing concern over the environmental impact of such spraying. Also, normal insecticide spraying would affect many other insects and animals' but the odour-baited targets kill only the tsetse itself.

In comparison, setting 'traps' is an extremely cost-effective method of dealing with the fly. Targets can be erected in minutes by a skilled team and can be moved once an area has been cleared. Further research is being done to identify odours to boost the :ttractiveness' of the targets and killing more flies at a time.